Winchester .204 brass major issue with loose primer pockets on first reloads
- Thread starter Cyres
- Start date
@ChesterP
Just out of interest, if you have saved a new GRT template with the trued velocities, have you had a play with length?
The .204r that I have encountered have had ample freebore, (I think they copied that from the Wby Mags when they designed the cartridge), so the only constraints will be mag length and actually having some shank left in the neck.
I've reloaded for a few using 5 powders and have ended up around the 2.275" COAL mark with each of them.
Pressure and velocities drop a bit, but BLT doesn't drop as much as would be expected due to the bullet being closer to the rifling.
I was going to have a play, but I don't know how far from the muzzle your Chrono was so the figures wouldn't have tied up.
Just a thought.
Just out of interest, if you have saved a new GRT template with the trued velocities, have you had a play with length?
The .204r that I have encountered have had ample freebore, (I think they copied that from the Wby Mags when they designed the cartridge), so the only constraints will be mag length and actually having some shank left in the neck.
I've reloaded for a few using 5 powders and have ended up around the 2.275" COAL mark with each of them.
Pressure and velocities drop a bit, but BLT doesn't drop as much as would be expected due to the bullet being closer to the rifling.
I was going to have a play, but I don't know how far from the muzzle your Chrono was so the figures wouldn't have tied up.
Just a thought.
ChesterP
Well-Known Member
Yes, indeed. The seating though of smaller bullets such as the 35 and 40 grn have very limited scope for seating further out without risking larger runout or case neck tension variations, which also affect accuracy but can be helpful in fine tuning loads. The chrony for my rifle loads was set at 2m from the muzzle, and this figure was entered in for correction of measured results at the muzzle for the model. A few fps won't make much difference to the model though. It's quite a neat thing because other environmental variables one might normally enter, for example within QL, are all worked back to one main factor, ie chamber pressures.
I think it beneficial to generally stick with at least one bullet diameter of shank and stay away from too hot a load but getting to full case can improve uniformity/reliability of ignition so often you end up improving consistency by reducing these variables, hence improve likely precision as tuning can be done using powder changes combined with slight seating variations. Eric Cortina has a whole raft of videos on this where he advocates sticking to one seating depth as the start point, irrespective of where the lands are (they move in a changing feast with round count) as OBT is what matters, then fine tune by moving back 2 to 3 thou at a time.
Whichever way you choose to do it, the main thing is to record and calibrate accordingly.
I think it beneficial to generally stick with at least one bullet diameter of shank and stay away from too hot a load but getting to full case can improve uniformity/reliability of ignition so often you end up improving consistency by reducing these variables, hence improve likely precision as tuning can be done using powder changes combined with slight seating variations. Eric Cortina has a whole raft of videos on this where he advocates sticking to one seating depth as the start point, irrespective of where the lands are (they move in a changing feast with round count) as OBT is what matters, then fine tune by moving back 2 to 3 thou at a time.
Whichever way you choose to do it, the main thing is to record and calibrate accordingly.
In complete agreement, particularly the starting seating depth, that is also my mantra, and the stubby, skinny little neck of the .204 does need some TLC to maintain consistent neck tension through sizing and/or annealing, particularly as it has 50000+ PSI exerted on a very small area.
Indeed. TBH it's probably the last cartridge for a less experienced reloader to have a play with.In complete agreement, particularly the starting seating depth, that is also my mantra, and the stubby, skinny little neck of the .204 does need some TLC to maintain consistent neck tension through sizing and/or annealing, particularly as it has 50000+ PSI exerted on a very small area.
I have no interest in them, they have no application here except for foxing and smaller things to blow up. Certainly not a target shooting sort of thing.
Whereas say a 223, (had one for many years, just a standard 12" twist, nothing more than 55gr bullets) or maybe even an old school 222 can do pretty much the same, maybe better even, and still allow me to shoot small deer with it.
Convince me why I would feel the need for one ,since I don't really shoot fox, or lesser vermin, unless I am asked to. If that was my mainstream activity I'd probably have some other chamberings in mind.
For reloaders a deep rabbit hole I suspect, to what end? Finnicky and fussy to say the least, never mind trying to find components, which, to be frank, are hardly mainstream.
ChesterP
Well-Known Member
Had a very interesting day with Cyres and we both learned a lot from running through a stack of tested load data and playing about with GRT.
In general, once MV's were used to calibrate OBT, tested loads corresponded closely with model predictions.
We found that the base model tended to under-estimate MVs for his 204 by an average of around 3% to a max of 6%.
This could be down to a number of reasons including variation in primer energy between brands, barrel differences etc but truing the velocity spat out in almost all cases the same accuracy nodes he managed to find when testing.
The other thing as expected was that case capacity variations can be the difference between being a hot load to being a dangerous one so it is essential to test and batch cases for reloading anything fast of moderate in this calibre. Magnum primers (in this case Remington 7.5's) also significantly raise initial chamber pressures for hotter loads to greater than 10% PMax.
The other interesting thing was variations between brass in terms of quality, consistency and case thickness. We annealed perhaps a few hundred cases and timings varied between makes by as much as 2 full seconds using propane in my "Raptor Calls" annealer.
The big surprise was how consistent Hornady 204 superformance cartridge cases were. Once fired cases were amongst the tightest on tolerance on case capacity and compared to Remington were far better quality cases. It's almost as cheap to buy a stock of superformance ammo in 204, and re-use the cases for reloading as to buy off the shelf cases with similar consistency.
Cyres also brought with him his 3-decimal place electronic scales (RRP £40) made by "on Balance" being their 50gr capacity Carat digital mini scales.
Despite the talk in the thread decrying such inexpensive scales as "cheap and inaccurate" (words to that effect) they were anything but. I checked them against my own £265 Lyman loading scale and another specialist calibrated digital scale and they were every bit as accurate with repeatable accuracy across the complete range down to 0.05 grains. Very popular with drug dealers allegedly!
We checked loads for 204, 243 and 223 and Cyres has gone away with his load data notebook with several suggested nodes for a range of powder and bullet combinations.
We also ran a load which Laurie had suggested worth trying using N140 (!) and the big surprise is that 26.7gr N140 produced a very good accuracy node with Berger 40gr varmint bullets for a BLT to OBT comparison 0f 0.90/0.91mS for a 91.5% load ratio and almost 99% burn rate in his 21.5 inch barrel. Not an obvious powder choice but on paper it looks to be an excellent match producing a moderate 3380fps at 52Kpsi. Next node below that seemed to be at 25.8gr for around 3270fps at a very moderate 47Kpsi.
Cyres has gone away to try this pairing but on paper N140 seems a far better suited powder with better burn and load efficiency for milder pressures than BL-C2. In fact, we found that BL-C2 was not the best choice and it ranked last in a group of 3 different powders because pressures were all quite high for poor burn rate in that barrel. It would fair better in a 24 to 26inch barrel I think.
Finally, a word of caution. As another check, we cross checked loads from various manuals, including Lyman and Vhit reloading tables. We found the odd tested load in some cals with Lyman were particularly hot so ALWAYS double check what the the test barrel and brass used was, especially for smaller calibres.
In general, once MV's were used to calibrate OBT, tested loads corresponded closely with model predictions.
We found that the base model tended to under-estimate MVs for his 204 by an average of around 3% to a max of 6%.
This could be down to a number of reasons including variation in primer energy between brands, barrel differences etc but truing the velocity spat out in almost all cases the same accuracy nodes he managed to find when testing.
The other thing as expected was that case capacity variations can be the difference between being a hot load to being a dangerous one so it is essential to test and batch cases for reloading anything fast of moderate in this calibre. Magnum primers (in this case Remington 7.5's) also significantly raise initial chamber pressures for hotter loads to greater than 10% PMax.
The other interesting thing was variations between brass in terms of quality, consistency and case thickness. We annealed perhaps a few hundred cases and timings varied between makes by as much as 2 full seconds using propane in my "Raptor Calls" annealer.
The big surprise was how consistent Hornady 204 superformance cartridge cases were. Once fired cases were amongst the tightest on tolerance on case capacity and compared to Remington were far better quality cases. It's almost as cheap to buy a stock of superformance ammo in 204, and re-use the cases for reloading as to buy off the shelf cases with similar consistency.
Cyres also brought with him his 3-decimal place electronic scales (RRP £40) made by "on Balance" being their 50gr capacity Carat digital mini scales.
Despite the talk in the thread decrying such inexpensive scales as "cheap and inaccurate" (words to that effect) they were anything but. I checked them against my own £265 Lyman loading scale and another specialist calibrated digital scale and they were every bit as accurate with repeatable accuracy across the complete range down to 0.05 grains. Very popular with drug dealers allegedly!
We checked loads for 204, 243 and 223 and Cyres has gone away with his load data notebook with several suggested nodes for a range of powder and bullet combinations.
We also ran a load which Laurie had suggested worth trying using N140 (!) and the big surprise is that 26.7gr N140 produced a very good accuracy node with Berger 40gr varmint bullets for a BLT to OBT comparison 0f 0.90/0.91mS for a 91.5% load ratio and almost 99% burn rate in his 21.5 inch barrel. Not an obvious powder choice but on paper it looks to be an excellent match producing a moderate 3380fps at 52Kpsi. Next node below that seemed to be at 25.8gr for around 3270fps at a very moderate 47Kpsi.
Cyres has gone away to try this pairing but on paper N140 seems a far better suited powder with better burn and load efficiency for milder pressures than BL-C2. In fact, we found that BL-C2 was not the best choice and it ranked last in a group of 3 different powders because pressures were all quite high for poor burn rate in that barrel. It would fair better in a 24 to 26inch barrel I think.
Finally, a word of caution. As another check, we cross checked loads from various manuals, including Lyman and Vhit reloading tables. We found the odd tested load in some cals with Lyman were particularly hot so ALWAYS double check what the the test barrel and brass used was, especially for smaller calibres.
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@mealiejimmy found much the same with his own induction annealer, doing it scientifically using a calibrated hardness tester. Likewise AMP have done a lot of research into the same thing. Not all brass is the same. Flame annealing is, I think a bit old-school, but the cost of entry for a commercial induction machine is still high.
Yes, as previously said, I too have had great luck with my inexpensive milligram resolution (0.02 grains) scales, I have two sets, different makes (just in case one goes down) and have also tested them with lab grade cal. weights.
I trust them far more than say relying on an automatic powder thrower, supposedly in the +/- 0.1 gr resolution class. Not that I have used one myself, but did help another evaluate his new Chargemaster Lite. He was pleased with it, I was not so much impressed, but kept my counsel on that. Or a typical digital scale sold for reloaders, again +/- 0.1 gr. Or a beam balance. Particularly as you, and Laurie have discovered, even 0.1gr absolute variations can make such a difference in small cases.
I suspect that in trueing GRT to match the real world MVs actually discovered, you have compensated for what might well have been a rather poor model of the specific powder concerned. If so it won't have necessarily made that model any better, over all conditions and chamberings, but might be worth feeding back your results to "The Community" to add to their knowledge base.
Though, curiously, I think that P-Max gave me a better insight, at the outset, with pure guesswork on my part. I also wonder where QuickLOAD fits in, unadjusted.
I've just repeated it, for your seemingly safe (uncorrected GRT) suggested load, using the same defaults I used the first time.
Your load: 30.7gr BL-C2 under a 35gr Berger Varmint @ 2.25COL, we have a measured velocity of 3872fps
Again severe overpressure predicted, 62,035 psi. Presumably GRT, uncorrected, didn't predict that, initially.
Tried again, this time at your (corrected) GRT suggested max safe node, 29.4gr BL-C2 for around 3710fps although BLT and OBT are a little apart at 0.91mS V's 0.85mS. Still looking a bit high on pressure but within upper limit.
So, I tweaked P-Max to match the muzzle velocity 3541 fps of your simulated (not yet tested ?) load the only way I know how, by adjusting powder space. Only took a few seconds. In fact the whole re-visit by me only took a few minutes. Anything with a web browser can access P-Max, no installation required. The hard work is all done behind the scenes, by his server.
So now we have two simulators theoretically aligned as far as predicted MV is concerned anyway.
It only took 1.8 grs water increase (0.12 cc) to match it. Within the sort of differences you've already measured between different makes of brass. 30.9gr water powder space, behind the bullet. Not the overflowing method followed by calculation of how much if that is lost when seating the bullet, I think the way that GRT, and QL do it. Might be interesting for you to try actually measuring it the borbal way, injected into the flash hole, with your bullet, seated at your depth to see how they compare.
Or a simple difference in primer could do that. Or neck tension, crimp etc.
You predict barrel time 0.91 ms. P=Max says 0.85 ms (exactly your predicted OBT)
Pressure is looking safe, but P-Max (corrected) still says you would be on the ragged edge by 31 gr. Get it wrong by half a grain, or a slight case capacity variation, change of primer, let your ammo get too hot in the sun etc. etc. and you could easily be over-pressure again. Which seems to be the recurring theme emerging.
Which model is closer, I have absolutely no idea. But at least the pressure now looks good.
I still think that weight-sorting a specific batch of one make of brass can give a pretty good insight into likely internal powder space variations in that batch, rather than laborious water measurements of each one. Assuming FL sized, and identical trim length. The way Norma do it, or suggest you do. And am prepared to discuss why, though I did bang on boringly about this on some much earlier thread, which escapes me ATM. Hint, brass density is about 8.5 grams/cc, but within quite a range of densities. That's for standard 60:40 brass. Cartridge brass is more like 70:30 copper to zinc, so probably a bit denser, depending on exactly what a particular manufacturer has chosen to use. Water 1.0. I reckon, other things being equal, that say measuring a 1gr variation in brass weight would give perhaps eight and a half times more precision in assessing powder space than say a 1gr water weight difference.
Anyway, great work, thanks for sharing. I've learned a lot from this, and your real-world experiences. Time I went to bed.
ChesterP
Well-Known Member
Thank you but I have to say there's some inaccuracies and supposition on your assessment of GRT which I'm unsure of what your basis is, so just needed to set the record straight, if for no other reason, to give you a steer in the right direction. You said that: "Again severe overpressure predicted, 62,035 psi. Presumably GRT, uncorrected, didn't predict that, initially."
Yes, it did. Uncalibrated it did predict the charge as unsafe (62,900psi with an MV of 3829fps, when tested MV was 3872fps hence actual pressures compensated for rose to closer to 65Kpsi) and is very close to QL on pressure predictions for just about all loads.
The one thing you can tweak to compensated for primers used is the Combustion Coefficient as this is another way to true the model. I figured that as primers can affect combustion ignition, then very slight tweaks to this figure can be used without changing anything else to land you smack bang on actual outputs. This makes sense as varying conditions can affect powder burn rates such as temperature and also brisance of primers used for ignition efficiency. The figure used in the standard model for Hogdon BCL-2 Combustion Coefficient (Ba) was 0.5391. This only has to increase fractionally to 0.5484, by some 0.0093 to get the model predicting exact MV, and likely truer pressures.
When looking to refine models you have to have tested data irrespective of the model used. The reason for the shortfall in velocities, as with many of these models, is that very few of them can accurately predict ignition efficiency accounting for variables such as primers which is why if you change a primer for example, it can be the sole arbitor of some of the velocity differences seen due to slight ignition hence combustion changes. Models have to use set ignition figures in initial pressure rises but at least there's the option of modifying the main model in lieu of velocity data or the combustion coefficient with the type of bullet and primer used (ie "standard" or "magnum"), entering "corrected" figures for "Ba" if using the same primers for a difference charge or as with QL, simply editing the powder energy figure to up the MV output. It's chicken and egg though as if you had the MV data you wouldn't need to do that.
Some barrels between two rifles of different makes, and sometimes even of the same make with identical bores and lengths can also exhibit velocity differences. There's a raft of variables which can affect actual V's modelled which is why we always have to test these things. A model exists with the main aim of predicting LIKELY pressures and nodes and in this respect, all the work so far done suggests that GRT is actually remarkably accurate or at least based on about 6 years worth of data I've been using to test it. But it does need more than a basic understanding to scratch its potential which means it is one you have to play around with until you understand how it works and know how it should be used.
Point is, and this one really does have to be accepted, that there are several very important factors which can never be exactly replicated across every piece of brass or across different powders or which accurately reflect slight changes in powder batches, hence why no mathematical model in its own right "knows" where these differences might lay and compensate for them. You have to use the likely culprits for changes to variables or at least use tested data and refine the models accordingly. At least GRT allows for this across a range of input variables providing you understand the significance of meddling with such variables. It therefore becomes a very useful tool for the advanced loader as well as a good way for the novice to throw out some safe data for start charges and work up slowly to within safe limits which I would caution anyone starting out to keep to within 10% of Pmax until test data can be obtained.
The one idiosyncrasy of GRT it does have is one which everyone needs to be aware of to avoid being caught out and that is due to the way that it runs sub routines and the implications of changing something on the same model by for example picking a charge adjustment highlighted in the OBT and entering that on the main charge input section throwing out the result as invalid. The reason for this is that the OBT model when pulled up and data entered must be deleted before you change it again or run for another set of loads otherwise the main charge entry does not link back to the calibration which is done on the OBT set up page. Also, sometimes throwing in a magnum primer option in the charge details on the main page can raise the initial pressures above 10% of Pmax which then invalidates the OBT times.
The shortfall in predicted velocities does not have to be far out to be reflected in OBT nodes, only a 2% variation with calibrated has quite an impact.
All in all, it is an extremely valuable tool which provides imho far more useful outputs than either QL or PMax whilst being more straightforward to tune with minimal ammo costs involved. That's not decrying Pmax nor QL, both of which are very useful checks on pressure but as with all these things, they have their limitations and each has its drawbacks.
I still feel minded to use GRT together with Pmax or QL as a cross check but only GRT once calibrated provides an output report which can be taken straight to the range to try a few predicted nodes once you have already picked and shot a handful of charges to get the velocity data needed. Then, to compensate for things like suppressors, which none of these programmes account for in models, you can play either side of predicted loads or work back in small increments seating depths until your rifle tuning as set up for the field, is perfected.
Yes, it did. Uncalibrated it did predict the charge as unsafe (62,900psi with an MV of 3829fps, when tested MV was 3872fps hence actual pressures compensated for rose to closer to 65Kpsi) and is very close to QL on pressure predictions for just about all loads.
The one thing you can tweak to compensated for primers used is the Combustion Coefficient as this is another way to true the model. I figured that as primers can affect combustion ignition, then very slight tweaks to this figure can be used without changing anything else to land you smack bang on actual outputs. This makes sense as varying conditions can affect powder burn rates such as temperature and also brisance of primers used for ignition efficiency. The figure used in the standard model for Hogdon BCL-2 Combustion Coefficient (Ba) was 0.5391. This only has to increase fractionally to 0.5484, by some 0.0093 to get the model predicting exact MV, and likely truer pressures.
When looking to refine models you have to have tested data irrespective of the model used. The reason for the shortfall in velocities, as with many of these models, is that very few of them can accurately predict ignition efficiency accounting for variables such as primers which is why if you change a primer for example, it can be the sole arbitor of some of the velocity differences seen due to slight ignition hence combustion changes. Models have to use set ignition figures in initial pressure rises but at least there's the option of modifying the main model in lieu of velocity data or the combustion coefficient with the type of bullet and primer used (ie "standard" or "magnum"), entering "corrected" figures for "Ba" if using the same primers for a difference charge or as with QL, simply editing the powder energy figure to up the MV output. It's chicken and egg though as if you had the MV data you wouldn't need to do that.
Some barrels between two rifles of different makes, and sometimes even of the same make with identical bores and lengths can also exhibit velocity differences. There's a raft of variables which can affect actual V's modelled which is why we always have to test these things. A model exists with the main aim of predicting LIKELY pressures and nodes and in this respect, all the work so far done suggests that GRT is actually remarkably accurate or at least based on about 6 years worth of data I've been using to test it. But it does need more than a basic understanding to scratch its potential which means it is one you have to play around with until you understand how it works and know how it should be used.
Point is, and this one really does have to be accepted, that there are several very important factors which can never be exactly replicated across every piece of brass or across different powders or which accurately reflect slight changes in powder batches, hence why no mathematical model in its own right "knows" where these differences might lay and compensate for them. You have to use the likely culprits for changes to variables or at least use tested data and refine the models accordingly. At least GRT allows for this across a range of input variables providing you understand the significance of meddling with such variables. It therefore becomes a very useful tool for the advanced loader as well as a good way for the novice to throw out some safe data for start charges and work up slowly to within safe limits which I would caution anyone starting out to keep to within 10% of Pmax until test data can be obtained.
The one idiosyncrasy of GRT it does have is one which everyone needs to be aware of to avoid being caught out and that is due to the way that it runs sub routines and the implications of changing something on the same model by for example picking a charge adjustment highlighted in the OBT and entering that on the main charge input section throwing out the result as invalid. The reason for this is that the OBT model when pulled up and data entered must be deleted before you change it again or run for another set of loads otherwise the main charge entry does not link back to the calibration which is done on the OBT set up page. Also, sometimes throwing in a magnum primer option in the charge details on the main page can raise the initial pressures above 10% of Pmax which then invalidates the OBT times.
The shortfall in predicted velocities does not have to be far out to be reflected in OBT nodes, only a 2% variation with calibrated has quite an impact.
All in all, it is an extremely valuable tool which provides imho far more useful outputs than either QL or PMax whilst being more straightforward to tune with minimal ammo costs involved. That's not decrying Pmax nor QL, both of which are very useful checks on pressure but as with all these things, they have their limitations and each has its drawbacks.
I still feel minded to use GRT together with Pmax or QL as a cross check but only GRT once calibrated provides an output report which can be taken straight to the range to try a few predicted nodes once you have already picked and shot a handful of charges to get the velocity data needed. Then, to compensate for things like suppressors, which none of these programmes account for in models, you can play either side of predicted loads or work back in small increments seating depths until your rifle tuning as set up for the field, is perfected.
Sorry, my misunderstanding. Presumably that load was one of the ones Cyres had previously tested at primer pocket expanding pressures, not one that you had suggested then tried recently. Sorry for any confusion.
This all makes sense. From watching some of Gordon's videos introducing the Beta to the public three years ago, he seemed rather obscure about the details of the powder models. Subsequently he made a video explaining in detail, this one:
From that I learned about how they were derived by his group of three people, and how (unlike QL) they did not simply use bomb pressure measurements, about which he was a little dismissive, believing that actual measurements in barrels gives a better picture, so why GRT has its own incompatible methodology whereby his is group of three conduct actual testing in rifles, using the "Pressure Trace II" equipment. With its limitations. Such as it does not directly measure pressure. It is not a substitute for the industry standard piezo transducer methods used in proofing, using universal receivers and test barrels.
He also explains, and names, how a few powder manufacturers have been very cooperative in providing their pressure bomb data, as a starting point. Particularly praising Reload Swiss. For the ones who were not, particularly all the US ones, it is basically done by reverse engineering of some sort by his inner circle, methodology still obscure. And refined by further real world (muzzle velocity) measurements of whatever quality, received from "the community".
Please do not think I am being in any way dismissive, just clarifying (I hope) my understanding of what the GRT powder models are, and how different they are from e.g. the QuickLOAD method, which we must admit is the industry standard, and why GRT did not set out to simply copy it.
Absolutely
I agree. For start charges. And an indication of likely Pmax at the upper limits. Do cross compare with published data also, even if its not for the exact bullet, case or primer. don't entirely rely on it, or any other simulator, to be infallible. Unfortunately the companies with reloading manuals to sell often still don't make this information available freely on the web.
I still have my own thoughts about the validity of OBT, and why going for a "half node" i.e. an antinode, might actually work better. At the node the barrel is whipping through it at maximum rate. Whereas at an antinode, whilst barrel deflection is at maximum, it is not whipping around, it's actually the most stable part of the vibration, provided it is consistent from shot to shot. Just my theory.
Dr Geoffrey Kolbe did some interesting research into something similar, in rimfire barrels. You might find it interesting reading: Using barrel vibrations to tune a barrel
Sounds reasonable. My concern about taking OBT at face value is that there are, IMO many variables, e.g. the mass of the receiver attached to the breech end of the barrel, and as you say the influence of any mass at the muzzle (moderator, "barrel tuner" etc,) never mind the fact that barrels are contoured, not a cylindrical rod, and made of steels with varying mechanical properties. But if it gets you in the ballpark, as you are finding, that's useful.
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ChesterP
Well-Known Member
I think you might think different of you use it and try the nodes, calibrate the model and compare MVs and groups. I've based my conclusions on a lot of tried and tested data. The whole node thing cannot be simplified to a half node is more reliable than a node for reasons already given and fwiw there is no difference in frequency based accelerations at any point on a node but at half nodes you can probably half the error by reducing spread. It's a moot point because that is dependant upon barrel profile as well as length as that affects sensitivity of a node. That's the key thing, working out which nodes are the least pressure sensitive and that can only be determined through trying it for yourself and your loads.
I fully accept that. And that GRT, uniquely, integrates a lot of the work in calculating the nodes, clearly quite well.
On an unrelated point though, I observe that, uniquely, Reload Swiss do state their allowable production variation for all their powders. I would guess that this would not be untypical of other manufacturers also,
If properly stored, the propellant powder remains safe to use for up to ten years.
Batch-to-batch tolerance:
v5 ±12 m/s
pmax ±250 bar
So, from one batch of powder to another, pmax could vary by as much as 7,252 psi. And that's when new, not after up to ten years later.
Not sure what v5 is, I'm guessing that might be velocity measured 5m from the muzzle in a particular test barrel and chambering.
Just another thing to be aware of, if developing precision loads, what seems spot-on with one batch of powder might not be quite so good with the next batch. I do know that ultra precision types sometimes stock up for the season with one batch of powder, for these reasons, then check again when they move on to the next batch. Their powder doesn't usually last long enough to age appreciably.
For any simulator the powder model is the heart of it, without a good one they are nothing. This is where I sense the GRT frustration in being unable to access the pressure bomb measurements from many powder manufacturers directly, It's fair enough to say that they use those, when they are given them, as a starting point then refine their model with testing in real rifles, including Pressure Trace II instrumentation, but otherwise their "reverse engineering" process in the absence of a starting point still seems pretty obscure to me, and in the hands of a select few, obviously. This is too serious to open up to others. I could hazard a guess as to how that could be done, rummaging through published load data, maybe even, ahem, running them through QL and "reverse engineering" from that for a starting point. Which of course would be borderline unethical.
The QuickLOAD chap does do his own testing with his own bomb, that's how he started out the whole simulation thing, and is clear about which powders, at least at the time he tested them, have good confidence. I found his document listing them all, identifying the ones he'd tested himself, those for which manufacturers had supplied data, others where he was not so confident, others where he had adjusted for the new formulations incorporating the trendy "copper fouling eliminator" or improved heat stability etc. However I can't ATM find that link again. Here is the closest to the source info:
POWDERS in QuickLOAD October 2021 - QuickLOAD
Note the annotations. preliminary data, approximation, C (copper solvent version) T (temperature improvement version) etc. In his original he also identifies those where the manufacturers gave their bomb data to him, and those which he had to test himself.
But here is the latest info showing the alterations and additions in the most recent update, to give a feel for how he keeps things up to date, and whether you would feel the need to pay for the latest update, if it affects some things that matter to you.
https://quickload.co.uk/wp-content/uploads/2022/07/CCE15072022.pdf
Also an old article from Chris Long, about fine tuning QuickLOAD V2
http://www.the-long-family.com/Tuning QL to achieve best results.pdf
TBH, still not really knowing what will be the future of GRT, (or I suppose of QL either, unless Dipl.-Ing. Hartmut G. Brömel has a good plan for succession), if and when I do feel the need for a fully featured simulator, I still might be tempted to pay for QL.
Meanwhile I'm just fascinated by the subject, as an Applied Physicist, and Engineer. And very boring (no I am not a Civil Engineer, joke).
On an unrelated point though, I observe that, uniquely, Reload Swiss do state their allowable production variation for all their powders. I would guess that this would not be untypical of other manufacturers also,
If properly stored, the propellant powder remains safe to use for up to ten years.
Batch-to-batch tolerance:
v5 ±12 m/s
pmax ±250 bar
So, from one batch of powder to another, pmax could vary by as much as 7,252 psi. And that's when new, not after up to ten years later.
Not sure what v5 is, I'm guessing that might be velocity measured 5m from the muzzle in a particular test barrel and chambering.
Just another thing to be aware of, if developing precision loads, what seems spot-on with one batch of powder might not be quite so good with the next batch. I do know that ultra precision types sometimes stock up for the season with one batch of powder, for these reasons, then check again when they move on to the next batch. Their powder doesn't usually last long enough to age appreciably.
For any simulator the powder model is the heart of it, without a good one they are nothing. This is where I sense the GRT frustration in being unable to access the pressure bomb measurements from many powder manufacturers directly, It's fair enough to say that they use those, when they are given them, as a starting point then refine their model with testing in real rifles, including Pressure Trace II instrumentation, but otherwise their "reverse engineering" process in the absence of a starting point still seems pretty obscure to me, and in the hands of a select few, obviously. This is too serious to open up to others. I could hazard a guess as to how that could be done, rummaging through published load data, maybe even, ahem, running them through QL and "reverse engineering" from that for a starting point. Which of course would be borderline unethical.
The QuickLOAD chap does do his own testing with his own bomb, that's how he started out the whole simulation thing, and is clear about which powders, at least at the time he tested them, have good confidence. I found his document listing them all, identifying the ones he'd tested himself, those for which manufacturers had supplied data, others where he was not so confident, others where he had adjusted for the new formulations incorporating the trendy "copper fouling eliminator" or improved heat stability etc. However I can't ATM find that link again. Here is the closest to the source info:
POWDERS in QuickLOAD October 2021 - QuickLOAD
Note the annotations. preliminary data, approximation, C (copper solvent version) T (temperature improvement version) etc. In his original he also identifies those where the manufacturers gave their bomb data to him, and those which he had to test himself.
But here is the latest info showing the alterations and additions in the most recent update, to give a feel for how he keeps things up to date, and whether you would feel the need to pay for the latest update, if it affects some things that matter to you.
https://quickload.co.uk/wp-content/uploads/2022/07/CCE15072022.pdf
Also an old article from Chris Long, about fine tuning QuickLOAD V2
http://www.the-long-family.com/Tuning QL to achieve best results.pdf
TBH, still not really knowing what will be the future of GRT, (or I suppose of QL either, unless Dipl.-Ing. Hartmut G. Brömel has a good plan for succession), if and when I do feel the need for a fully featured simulator, I still might be tempted to pay for QL.
Meanwhile I'm just fascinated by the subject, as an Applied Physicist, and Engineer. And very boring (no I am not a Civil Engineer, joke).
ChesterP
Well-Known Member
Yes, each new powder batch needs loads checking. They can all have variations rendering a hot load in one batch dangerous in another, or conversely, a low load, dangerously underpressure if loaded at the bottom. It's why I shoot a couple at my pet load for each new batch and re-calibrate GRT to see if the node has changed (invariably it does). I keep seating exactly the same, and loads get tweaked up or down a little until I have the same MV as for the previous batch. My degree was in Civil Engineering so I've heard it all before! I've an amateur interest in applied sciences and have done extensive further studies in acoustic physics and applied ballistics over the past 15 to 20 years or so. Doesn't make me expert in anything, but is an active interest. Reloading is a series of rabbit holes but my real interest is more in internal and external ballistics.
ChesterP
Well-Known Member
New data now obtained from field testing of GRT loads!
GRT modelled for Nostler brass with case capacity of 2.086cm3 and COAL of 2.25 with Remmy 7.5 SR primers at 25.9gr H335:
GRT model: MV = 3,463ft/s at 54,330psi for 96.4% powder burn in 21.5" barrel at close on optimum barrel time node (ie accuracy node). Without entering measured velocities the model was adjusted for magnum primers.
Field test gave 3,490fps and bug hole group
Best GRT node given as 25.4gr once model was calibrated with field test MV readings.
Conclusive test which underlines how darned close GRT can safely get you to an ideal load when brass prep is done uniformly and decent data obtained to calibrate it. Also proof that it allows very efficient load development without the need to shoot ladder tests although pressure testing for pressure signs is still sensible. There is a caveat. Using the magnum primers, there's little evidence until grossly overpressure loads reached of any signs from primers so it's not sensible to use primer condition to assess safety of load. Not exceeding powder makers recommended upper limits is still recommended.
GRT modelled for Nostler brass with case capacity of 2.086cm3 and COAL of 2.25 with Remmy 7.5 SR primers at 25.9gr H335:
GRT model: MV = 3,463ft/s at 54,330psi for 96.4% powder burn in 21.5" barrel at close on optimum barrel time node (ie accuracy node). Without entering measured velocities the model was adjusted for magnum primers.
Field test gave 3,490fps and bug hole group
Best GRT node given as 25.4gr once model was calibrated with field test MV readings.
Conclusive test which underlines how darned close GRT can safely get you to an ideal load when brass prep is done uniformly and decent data obtained to calibrate it. Also proof that it allows very efficient load development without the need to shoot ladder tests although pressure testing for pressure signs is still sensible. There is a caveat. Using the magnum primers, there's little evidence until grossly overpressure loads reached of any signs from primers so it's not sensible to use primer condition to assess safety of load. Not exceeding powder makers recommended upper limits is still recommended.
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