Winchester .204 brass major issue with loose primer pockets on first reloads

[Foxyboy43]

“TBH I never had a problem with them in my 223 and used several thousand, but never loaded that hot, just standard book loads.”.
In the spirit of SD friendship IMHO in Sharpie’s short sentence is perhaps the best advice a fox-shooting reloader will ever have, regardless of chambering. I can well understand the quest for ultimate accuracy in target shooting circles but to chase this elusive zephyr by exceeding manufacturer’s loads for fox shooting is dancing with the devil - especially in such a small volume case as the .204. The .204 is an extremely accurate and, for foxes, a deadly round at amazing distances utilising only mid-range powder manufacturer’s recipes - for example from Viht’s excellent site:-

N530

1,50

23.1

1013

3323

1,67

25.8

1236

4055

So a 2.7 gns increase of powder gives an extra 700 fps at the muzzle for a 40gns vmax but if you are shooting sub-moa with say, 24.5 gns, why burn extra powder, incur additional cost and increase wear and tear on your rifle? You will still drop foxes at distance and it certainly will not notice any difference.
Now call me old-fashioned and to avoid sounding like a silly old fool (moi?) the above view is very much aimed at the inexperienced (.204 and other small cases) reloader who may be unduly influenced by detailed conversations between clearly savvy posters and thus be tempted to go for the “big bang” without proper testing of progressive loads. It is also based on 40 years or more reloading of everything from .222 to 8mm and shooting very many foxes and quite a few deer.
Just my threehappence (younger readers ask your grandad) worth. Helmet on, chin-strap tightened……

 

[Foxyboy43]

My god! Two great statements in one morning - thank you HeymS20.
“But I am expecting lots of incoming, and note I said “hunting” ammo. A lot of serious reloaders will spend a lot of time adjusting the length of the bullet in the case, applying different neck tensions etc etc. This may make the difference between winning a match and picking up silverware, or doing the clearing up whilst others celebrate.

For me, I want a load that puts the bullet through the vitals of any deer, boar or fox, that has a trajectory where I don’t have to worry about range or wind, or for that matter the exact angle that the deer presents.”.
Bless

 

[ChesterP]

The long and short of it is there are several factors here combining with clearly fairly hot loads: Case volume between batches, powder batch (variations?), primer choice and brass quality.

Cyres is popping up next week, so we'll look at case volumes again and I'll run his loads through the GRT load development software and enter the bullet details so we get pressures compensated for actual case (spare) capacity under the projectiles. We'll run with the magnum primers being used (CCI400's are out!) and see what the nodes are for measured MVs in that rifle as all these things can be modelled and calibrated within GRT. That allows for OBT nodes to be identified (however close or not they might be) and we then have the option of coming up with milder accurate loads just as capable at dropping charlie without all the drama of blowing primers or going overpressure. Sometimes it pays to just take stock and to stay away from hot loads in smaller cases where any variance in case volume, temperatures and the like can push a hot load to a dangerously over pressure load.

 

[ChesterP]

Just entered all the data including measured MVs and case capacity, and max safe node for OBT appears to be 29.6gr for 3700fps (21.5" barrel) at 55K PSI. Next lowest is 28.4gr for 3513fps. 31.2 showing massively overpressure at 67,600psi. Data was trued for measured MVs to calibrate modelled pressures.

 

[NP435]

I use br4 in 204 and 223, loaded to the max book data not over, no issue with soft primer cups, the only loose primer pockets were in 22-250 at 9 firings, at that point they went in my recycle bucket. One thing you may consider is each projectile brand differs in jacket thickness and softness this will effect pressure. so will a longer bearing surface. I don't ever exceed max powder charges and I tend to test at temps over 30c.

 

[Sharpie]

Just entered all the data including measured MVs and case capacity, and max safe node for OBT appears to be 29.6gr for 3700fps (21.5" barrel) at 55K PSI. Next lowest is 28.4gr for 3513fps. 31.2 showing massively overpressure at 67,600psi. Data was trued for measured MVs to calibrate modelled pressures.

Which is even worse than what I predicted in post #12, simply using P-Max's suggestion of a starting point for powder space, in the absence of any other knowledge/measurement. What was the measured case capacity BTW, I'd like to give that one last spin to see how closely P-Max will then match GRT.

Possibly 10,100 psi overpressure in a 57,500 psi (MAP) rated case. Frankly I think his brass, and primers, were doing very well to have held up to that for even just the first firing. I wouldn't expect them to be in a good state after doing that.

Of course these are only simulations, but I think can be pretty good indications, particularly if tweaked to match your chrono results even more closely.

Whilst I also have GRT, I've only just skimmed the surface so far. What do you think of the optimum barrel time theory, have you found it to get close to real world ? P-Max also predicts barrel time, interesting to see how that matches GRT's numbers.

I've been thinking of making a spreadsheet for the-long-family.com formula, I presume this is something like what GRT does for you. Use that to calculate OBT for some nodes, then adjust charge weight in the simulator to get to those times. Maybe someone has already done that and published it.



Usually I just use published loads, ideally for the exact bullet, otherwise something the same weight or a little more, run them through P-Max as a sanity check looking for good correlation with the published muzzle velocities, and pressure if stated.

Then, if feeling gung-ho, when loading a normal sort of bore case, not overbore and small capacity like a 204 Ruger, (Caveat: I do not recommend this of course) dive in with a published load midway between start and max. If that works OK, leave it there, unless I then start looking a bit more closely for target shooting precision. Mid way ought to be a tolerant place to be, regarding the inevitable variations in components.

Long range precision types of course have their own ideas, stock up on components all from one manufacturing batch, fine tune their QuickLOAD parameters to match actual results, and load to the max. for the edge that gives them. Even then at some matches they have to submit their rifles and ammo for chronoing, to make sure they've not over-done it, or are cheating.

Far far away from what most of us need for our goals.

I've not been developing loads for several years now, nor was ever serious about target shooting, though I've had my moments in club competitions, so am pretty much a theoretician these days, just follow this stuff vicariously for the fascination.

I do wonder where @Cyres got his 31.9 gr figure from that he worked all the way up to, on a warm day. QuickLOAD I suppose. Possibly a little pilot error when wrangling that ?

 

[ChesterP]

I modelled both sets of brass so one was 2.16cm3 and the second was 2.077cm3. In terms of OBT it only works well once calibrated.

I've taken years worth of load data for each of my cals including case capacities, loads, tested MV's and groups, and entered a selection for each cal into GRT.

The results were a bit hit and miss if you left it to the program's outputs without validation but still reasonably close for all but some of my 223 loads.

308 was spot on, as in precisely matching for two nodes (155 sierra hpbt gamekings) using N140 and Lapua brass. My accuracy nodes as tested were 44gr and 42.8gr. GRT gave me 44.03gr and 42.93gr for velocities within 20fps of what I measured. It's the first program I've used to get that close, so that's confidence inspiring.

However...small variations in smaller case capacities can throw it out a fair bit so in order to get meaningful outputs, the fire formed case capacities have to be accurate or rubbish in = rubbish out thing applies. My go to loads for the #1390 bullet have been nodes for PPU with measured case capacity of 30.7gr were 23.6gr and another at 22.8gr using N133. GRT predicted 22.85gr for the lower node and 23.6 on the nose for the higher one. That was using an averaged MV for the load step test I did for my last PPU batch. Again, spectacularly accurate output. Moving to my Sako cases, it was a little further away but I suspect that's more down to my Chronograph error on that specific day as the best groups shot were roughly in agreement with one of the gRT accuracy nodes on barrel time.

The way it calculates initial pressures relies on accurate data in. As long as you're careful with everything from case capacities (it deducts bullet seating depth from COAL to give actual case capacity) to verifying at least one MV for a specific charge, enter the correct barrel length and twist, and I'm impressed enough to be confident in the OBT predictions being spot on or very close indeed. Whilst QL does have a facility for outputting barrel times, it doesn't correlate them with bullet lead time at 10% of Pmax to give approximations for OBT, GRT does exactly this which for me is one reason for using it, as well as checking on safe pressures.

The only drawback is shooting Palma brass (308) or SR Creedmoor (6.5) where initial pressures seem high in GRT because I think it bases them in LR brass. For those cals as long as you true the model for measured velocities, it will alter Pmax accordingly which will then allow reasonably good OBT estimates, For standard cases I'm putting my neck on the block and saying it gets very close indeed, at least with N133, N140 and RS62. RS50 results were a little off resulting in slightly lower velocities than I got

 

[Lancaster]

I modelled both sets of brass so one was 2.16cm3 and the second was 2.077cm3. In terms of OBT it only works well once calibrated.

I've taken years worth of load data for each of my cals including case capacities, loads, tested MV's and groups, and entered a selection for each cal into GRT.

The results were a bit hit and miss if you left it to the program's outputs without validation but still reasonably close for all but some of my 223 loads.

308 was spot on, as in precisely matching for two nodes (155 sierra hpbt gamekings) using N140 and Lapua brass. My accuracy nodes as tested were 44gr and 42.8gr. GRT gave me 44.03gr and 42.93gr for velocities within 20fps of what I measured. It's the first program I've used to get that close, so that's confidence inspiring.

However...small variations in smaller case capacities can throw it out a fair bit so in order to get meaningful outputs, the fire formed case capacities have to be accurate or rubbish in = rubbish out thing applies. My go to loads for the #1390 bullet have been nodes for PPU with measured case capacity of 30.7gr were 23.6gr and another at 22.8gr using N133. GRT predicted 22.85gr for the lower node and 23.6 on the nose for the higher one. That was using an averaged MV for the load step test I did for my last PPU batch. Again, spectacularly accurate output. Moving to my Sako cases, it was a little further away but I suspect that's more down to my Chronograph error on that specific day as the best groups shot were roughly in agreement with one of the gRT accuracy nodes on barrel time.

The way it calculates initial pressures relies on accurate data in. As long as you're careful with everything from case capacities (it deducts bullet seating depth from COAL to give actual case capacity) to verifying at least one MV for a specific charge, enter the correct barrel length and twist, and I'm impressed enough to be confident in the OBT predictions being spot on or very close indeed. Whilst QL does have a facility for outputting barrel times, it doesn't correlate them with bullet lead time at 10% of Pmax to give approximations for OBT, GRT does exactly this which for me is one reason for using it, as well as checking on safe pressures.

The only drawback is shooting Palma brass (308) or SR Creedmoor (6.5) where initial pressures seem high in GRT because I think it bases them in LR brass. For those cals as long as you true the model for measured velocities, it will alter Pmax accordingly which will then allow reasonably good OBT estimates, For standard cases I'm putting my neck on the block and saying it gets very close indeed, at least with N133, N140 and RS62. RS50 results were a little off resulting in slightly lower velocities than I got

That pretty much mirrors what I have found with GRT, and it is easier than using an OBT table and playing with adjusted results in QL which I have done by unlocking and changing the powder burn characteristics to match observed velocities.
Having said that I have had some good results and also helped out a fair few people to get very close to, if not bang on a node using OBT tables and QL.
Once you get into this rabbit hole it is bloody hard to get back out again

 

[Sharpie]

Once you get into this rabbit hole it is bloody hard to get back out again

Just so. Though I do have a certain skepticism about OBT, at least some of the originator's ideas, and his propensity to enumerate things to nine decimal places, whilst conveniently ignoring the fact that, no, not all barrel steels have the same same identical properties as regards the factors that might be relevant, nor should be expected to vibrate the same irrespective of profile, contour, fluting, nevermind fancy carbon wrapped things.

 

[ChesterP]

Just so. Though I do have a certain skepticism about OBT, at least some of the originator's ideas, and his propensity to enumerate things to nine decimal places, whilst conveniently ignoring the fact that, no, not all barrel steels have the same same identical properties as regards the factors that might be relevant, nor should be expected to vibrate the same irrespective of profile, contour, fluting, nevermind fancy carbon wrapped things.

Yes, I agree. However, the correlation with tested results in all of my rifles suggest for me at any rate, it's pretty much mirrored my most accurate nodes, hence out of all the methods including Satterlee, OCW etc, I've found that loading a few steps either side of the predicted OBT times gets results almost every time as long as the data input is accurate. That includes recording tested MVs for a couple of load steps. Do that and as where with QL you have to adjust burn rates to mirror velocities in your rifle, with GRT you true the velocity in the model for a specific charge and it recalibrates for pressures and OBT.

The correlation is tied in with chamber pressures and for those familiar with "P" wave theory and rifle barrel harmonics, it helps explain why barrel length is critical in determining accurate nodes. Rather than repeat it all here, those interested can read about Chris Long's studies into this and he was credited with being the first to properly correlate barrel times and pressure wave theory. A good explanation is available on this link: https://www.shootingsoftware.com/barrel.htm

 

[Sharpie]

A good explanation is available on this link: https://www.shootingsoftware.com/barrel.htm

Thank you for that link. Again another chap with his own ideas, and his product to sell.

Fortunately I've never come across ringed barrels simply caused by weird pressure events, never mind with the ends blown off them due to his "secondary spikes" idea.

He also got this bit wrong:

Note: Customers who send ammo to commercial labs rarely become aware of severe secondary pressure spikes for two reasons. Test barrels are typically only 20 inches long. The above examples of severe secondary pressures should not occur in a 20 inch long tight bore.

Standard test barrels are actually 24" long.

BTW, the Birmingham Proof House will test your ammo for you, for a very reasonable fee, last time I enquired they'd do it for £25, using pukka piezo transducers in the approved way,, even give you the pressure trace, not just the Pmax and MV.

Not some strain gauge that you've glued onto your barrel. Which I could do very easily, condition it ,then send it to a digital storage 'scope to capture. Even glue on a couple of accelerometers at the muzzle as well. Might make an interesting student project I suppose

I'll still carry on using some of my favourite ball powders too, even though he thinks they are the devil's work.

 

[Lancaster]

Thank you for that link. Again another chap with his own ideas, and his product to sell.

Fortunately I've never come across ringed barrels simply caused by weird pressure events, never mind with the ends blown off them due to his "secondary spikes" idea.

He also got this bit wrong:

Note: Customers who send ammo to commercial labs rarely become aware of severe secondary pressure spikes for two reasons. Test barrels are typically only 20 inches long. The above examples of severe secondary pressures should not occur in a 20 inch long tight bore.

Standard test barrels are actually 24" long.

BTW, the Birmingham Proof House will test your ammo for you, for a very reasonable fee, last time I enquired they'd do it for £25, using pukka piezo transducers in the approved way,, even give you the pressure trace, not just the Pmax and MV.

Not some strain gauge that you've glued onto your barrel. Which I could do very easily, condition it ,then send it to a digital storage 'scope to capture. Even glue on a couple of accelerometers at the muzzle as well. Might make an interesting student project I suppose

I'll still carry on using some of my favourite ball powders too, even though he thinks they are the devil's work.

Going back to ChesterP's point about OBT, instead of googling stuff, why don't you try doing in it in practice, use GRT or QL and OBT and put in your own data from your own loads and then actually fire some rounds and see if it correlates, then try finessing your loads using the suggestions to see how it works.
I am getting the firm impression that you are an armchair expert who actually knows sod all about many of the subjects that you fill page after page of on this site, whilst using the site owners bandwidth, which has to be paid for, with regurgitated stuff rom the internet.

 

[Sharpie]

Going back to ChesterP's point about OBT, instead of googling stuff, why don't you try doing in it in practice, use GRT or QL and OBT and put in your own data from your own loads and then actually fire some rounds and see if it correlates, then try finessing your loads using the suggestions to see how it works.

Maybe one day, as I said earlier I am not doing much shooting at the moment, never mind load development.

And unfamiliar with GRT as yet, so very interested to hear ChesterP's experiences using it for OBT work. Looking to maybe doing so myself one day. I don't have Quickload. Just as I might be interested in your knowledge, since it is not a topic that otherwise receives much attention here, if you would care to share a little detail of "I have had some good results and also helped out a fair few people to get very close to, if not bang on a node"

My dabbling with simulations has simply been tinkering with P-Max and comparing it with published load data, with which it seems to correspond very well, which is why I nowadays have confidence that simulators can provide good correlation.

My old days of load development were primitive by such standards, when borrowing the club chrono. was considered the height of sophistication. Long before e.g. Magnetospeeds and Labradars existed. And QuickLOAD had only just been invented, and still viewed with some skepticism.

Plus I've only been shooting centrefire for about 25 years, and shot my first deer about 12 years ago, So am a complete newbie by some people's standards.

I am getting the firm impression that you are an armchair expert who actually knows sod all about many of the subjects that you fill page after page of on this site, whilst using the site owners bandwidth, which has to be paid for, with regurgitated stuff rom the internet.

Yes, I spend far too much time keeping my mind active and interested researching and learning from others. I try to never stop learning, nor get set in my ways.

On many other topics I do actually know quite a lot. But I'm not going to post a CV here, nor feel any desire to boost my ego with grandiose postings.

You do seem to have rather a chip on your shoulder about me for some reason. I think the site owners can look after their own business running this forum, which, as for all such successful things, requires frequent content contributions to keep it relevant and of interest to as wide an audience as possible.

I observe that you have contributed 400 posts since you joined five years ago. Some of them quite sarcastic, a personality trait that I try to avoid indulging in myself.

Please, in future, try to resist stalking and having sly digs at me, it's not big, nor clever.

 

[ChesterP]

Thank you for that link. Again another chap with his own ideas, and his product to sell.

Fortunately I've never come across ringed barrels simply caused by weird pressure events, never mind with the ends blown off them due to his "secondary spikes" idea.

He also got this bit wrong:

Note: Customers who send ammo to commercial labs rarely become aware of severe secondary pressure spikes for two reasons. Test barrels are typically only 20 inches long. The above examples of severe secondary pressures should not occur in a 20 inch long tight bore.

Standard test barrels are actually 24" long.

BTW, the Birmingham Proof House will test your ammo for you, for a very reasonable fee, last time I enquired they'd do it for £25, using pukka piezo transducers in the approved way,, even give you the pressure trace, not just the Pmax and MV.

Not some strain gauge that you've glued onto your barrel. Which I could do very easily, condition it ,then send it to a digital storage 'scope to capture. Even glue on a couple of accelerometers at the muzzle as well. Might make an interesting student project I suppose

I'll still carry on using some of my favourite ball powders too, even though he thinks they are the devil's work.

I wasn't pushing his software nor upholding his opinions on test barrel lengths. I was saying that he got it right on the pressure wave theory because, he, Litz and a raft of other well respected top shots and ballisticians now agree on this pressure theory, not least because it correlates well with actual tests which is what science is all about...ie looking to best describe things we experience then testing those theories to see if they hold water.

In this case, OBT does indeed have a direct relationship with both barrel length and pressures. I have worked up a lot of loads and correlated them against an MV corrected model in each case and in almost all cases they either come close enough to be within a pressure insensitive zone or have been spot on. That. for me anyway, speaks volumes. It is free to anyone who wants it, and no-one needs to understand pressure wave theory to use it, just use a Chrony to test your loads, enter the data, true the data and have reasonable confidence in the outcome. It also correlates well to trued QL outputs for pressure providing that powder energy figures are correct.

It's similar (analogous) in a way to trying Strelok using either a modified G7BC or MV until you get the drops at step distances which mirror those shot. A great many people use Strelok and know the value of this function, which is first time hits at distance, subject to the usual caveats of understanding how pressure sensitive powders might be to temperature fluctuations and accounting for environmental conditions etc.

The way a barrel actually behaves in relation to profile etc has more I think to do with how many and how wide the pressure insensitive nodes are. For example, bench rest shooters might find that their heavy bull barrels which limit sinusoidal whip amplitudes might be less sensitive, hence have wider insensitive (ie wider accuracy) nodes than a thin sportster barrel profile. This doesn't in any way invalidate pressure wave theory, it just means for those shooting target competitions, they will choose a profile most suited to long shot strings where they have to have more uniform precision whereas sporting rifle users may have to accept that their nodes are much narrower, hence GRT becomes arguably even more useful in getting them close as efficiently as possible without the need to get through 50 or more bullets in load development to find those accuracy nodes. The rest is up to fine tuning and good shooting technique.

In the same way you can take actual measurements (MV's) and do similar with GRT to obtain your nodes which thanks to the fact that pressure wave theory was discovered and used in computational ballistic analysis, we have the means to 1) check that our loads are well within allowable pressures and 2) find good approximations for our accuracy nodes.

Discussing the relative merits or not of various theories when they have been both established and verified is up to each person. How well they have been explained or described is a moot point as science usually evolves, but keeping that open mind to learning is valuable, and thankfully we have GRT because of the dedication of Gordon (RIP) which I'd argue is one of the most valuable and usable ballistic tools to come out in decades.

 

[Sharpie]

Thank you @ChesterP for that considered reply. When I have time I will try to scratch the surface of GRT. I had been putting that off, not knowing how things might progress after Gordon died, thinking it might become a frozen moment in time. I hope that plans for succession will continue.

Thank you so much.

And I do hope you can help @Cyres next week. You seem to be a generous and helpful person.

 

[Lancaster]

Maybe one day, as I said earlier I am not doing much shooting at the moment, never mind load development.

And unfamiliar with GRT as yet, so very interested to hear ChesterP's experiences using it for OBT work. Looking to maybe doing so myself one day. I don't have Quickload. Just as I might be interested in your knowledge, since it is not a topic that otherwise receives much attention here, if you would care to share a little detail of "I have had some good results and also helped out a fair few people to get very close to, if not bang on a node"

My dabbling with simulations has simply been tinkering with P-Max and comparing it with published load data, with which it seems to correspond very well, which is why I nowadays have confidence that simulators can provide good correlation.

My old days of load development were primitive by such standards, when borrowing the club chrono. was considered the height of sophistication. Long before e.g. Magnetospeeds and Labradars existed. And QuickLOAD had only just been invented, and still viewed with some skepticism.

Plus I've only been shooting centrefire for about 25 years, and shot my first deer about 12 years ago, So am a complete newbie by some people's standards.



Yes, I spend far too much time keeping my mind active and interested researching and learning from others. I try to never stop learning, nor get set in my ways.

On many other topics I do actually know quite a lot. But I'm not going to post a CV here, nor feel any desire to boost my ego with grandiose postings.

You do seem to have rather a chip on your shoulder about me for some reason. I think the site owners can look after their own business running this forum, which, as for all such successful things, requires frequent content contributions to keep it relevant and of interest to as wide an audience as possible.

I observe that you have contributed 400 posts since you joined five years ago. Some of them quite sarcastic, a personality trait that I try to avoid indulging in myself.

Please, in future, try to resist stalking and having sly digs at me, it's not big, nor clever.

Sorry, didn't intend any digs to be sly, I was hoping that they were quite open?
Definitely not stalking you, but I will happily highlight instances when I encounter verbal Diarrhoea.
Perhaps I should just use the Ignore feature as I find you to be incredibly irritating.

 

[ChesterP]

Thank you @ChesterP for that considered reply. When I have time I will try to scratch the surface of GRT. I had been putting that off, not knowing how things might progress after Gordon died, thinking it might become a frozen moment in time. I hope that plans for succession will continue.

Thank you so much.

And I do hope you can help @Cyres next week. You seem to be a generous and helpful person.

Thank you Sharpie. I'm just someone who shoots (and worked with) guns most of my adult life, as I suspect many others contributing on SD are. Being an engineer, I'm struck with the engineer's disease which is looking at the detailed aspects of things which can often be as much of a hindrance as a help but I do find that having a curious and questioning mind usually helps learning. There's a wealth of experience on this site and I do see it as a community where as with most communities, it takes all sorts but if we can help one another out then all the better. I'm only too happy to help out others even if I consider my own knowledge eclipsed by a fair few on here. I hope that Cyres trip is worthwhile and if nothing else, at least he'll get his brass annealed and can go out and try again . We have actually been in contact and based on his measured data, we've worked up what we think will be safe and decent loads for him to try, between us. If there's anyone else in the Glos area that needs a little input or help, I'm always more than happy to help out.

 

[NP435]

I checked the Berger data 28.6 BLC2 is the max charge with the 35 grn projectile. Now I wonder what the data source was. There is a reason to check published data.
Now the pierced and blown primers make sense its.........................................overpressure, no wonder the primer pockets expanded.

 

[Laurie]

The long and short of it is there are several factors here combining with clearly fairly hot loads: Case volume between batches, powder batch (variations?), primer choice and brass quality.

Just so!

Case capacity variations have become my latest obsession and Bore-A-Thon topic. The long and the short of it is that the closer you run to absolute pressure limits, the less room exists for minor loading procedure errors and ANY variation introduced by component change(s). Different make cases frequently have enough capacity difference to have a material effect on peak pressures; same make but different batches less likely, but by no means unknown. I have Lapua 'Match' 223 Rem brass in use some of which goes back 15 years and there is a half-grain water capacity change over various batches. QuickLOAD calculates c. 2,000 psi change in peak pressure over that range and I'd expect something similar with the 204. Throw in that, like most people, I'd back Lapua any day against Winchester for manufacturing consistency. Change primer, zero beam scales marginally 'out' and inject some small unnoticed variation in charges thrown, and if those changes go one way, a hot load becomes a dangerous one!

On priming with a Lee primer it was clear that there was a huge issue with the primer pockets. Some no resistance at all and the primer fell out other were minimal resistance others were a bit better.

Assuming I've read your post right and this was new brass, I'd have rejected the contents of the entire bag and returned it even if some appeared OK when using the priming tool. Case integrity is so fundamental to safety that the risk in using any case from such a lot is far, far too high. Manufacturers do occasionally get it very wrong - I have the remains of a carton of 1980s era Norma 270 Win 130gn PSP factory ammo somewhere from a batch that was subsequently recalled. Nine out of ten performed fine; the tenth produced an MV in line with those of the others, so wan't obviously overloaded, but the case-head and lower body expanded to such a degree that the rifle bolt had to be hammered open and the spent primer fell out into the magazine well. No need to mike the case-head or web - simple inspection showed the bulging.

What I cannot understand is why having developed and tested a load at 30c last summer and loaded 200 rounds why suddenly has it gone massively over pressure?

Stainless match-quality barrels have a nasty habit of producing significantly higher pressures / MVs after 150-250 rounds down them, even after a careful running-in exercise. Some barrels seem to avoid this fate; others suffer badly. As part of a Hodgdon VarGet / H4895 alternatives exercise I'm running using 223 with the 77gn SMK, I recently remeasured my baseline MVs for the two 'control' powders as their original readings came from a new barrel with 65-120 rounds down it. The VarGet load saw an MV increase from 2,935 to 3,000 fps MV, but unfortunately I had to use a different VarGet lot and that likely accounted for at least some of the change. H4895 using the same lot as the original test saw 2,975 fps rise to 3,015 with all components the same as before. Both increases would have needed significant pressure increases. This phenomenon is being increasingly commented on in target shooting forums, and I know one gunsmith who warns recipients of a newly rebarreled rifle not to load up to max immediately and to recheck MVs and groups at around the 200 rounds mark. (MVs were measured on a Labradar, so should be reliable.)

3 cases went of with a large bang and the primer cases were blown out of the pockets in that on ejection the primer fell out on the 3rd I removed the bolt to extract the fired case. The heads were covered in soot and an extractor mark left on the case head.

Ow! That made me wince! Three was two examples too many - ie when that happens, not a single additional cartridge from that lot should be fired. I don't want to sound 'preachy' on this, but well remember a fellow shooter working loads up in batches of five many years ago. Something went disastrously wrong and he exited the range refusing to admit anything had happened or explain how he had a cut eyebrow with blood running down his face. He did admit to his best shooting friend that he knew his top load was OTT from the primer condition and hard bolt opening, but thought he'd 'get away with it' firing the other four off and avoid pulling them at home. He did get away with it for three further shots; the final one saw a case failure that blew the extractor off and out and that was likely what hit him. Half, three-quarters lower strike and it would have been a major injury and lost eye.

 

[NP435]

Just so!

Case capacity variations have become my latest obsession and Bore-A-Thon topic. The long and the short of it is that the closer you run to absolute pressure limits, the less room exists for minor loading procedure errors and ANY variation introduced by component change(s). Different make cases frequently have enough capacity difference to have a material effect on peak pressures; same make but different batches less likely, but by no means unknown. I have Lapua 'Match' 223 Rem brass in use some of which goes back 15 years and there is a half-grain water capacity change over various batches. QuickLOAD calculates c. 2,000 psi change in peak pressure over that range and I'd expect something similar with the 204. Throw in that, like most people, I'd back Lapua any day against Winchester for manufacturing consistency. Change primer, zero beam scales marginally 'out' and inject some small unnoticed variation in charges thrown, and if those changes go one way, a hot load becomes a dangerous one!



Assuming I've read your post right and this was new brass, I'd have rejected the contents of the entire bag and returned it even if some appeared OK when using the priming tool. Case integrity is so fundamental to safety that the risk in using any case from such a lot is far, far too high. Manufacturers do occasionally get it very wrong - I have the remains of a carton of 1980s era Norma 270 Win 130gn PSP factory ammo somewhere from a batch that was subsequently recalled. Nine out of ten performed fine; the tenth produced an MV in line with those of the others, so wan't obviously overloaded, but the case-head and lower body expanded to such a degree that the rifle bolt had to be hammered open and the spent primer fell out into the magazine well. No need to mike the case-head or web - simple inspection showed the bulging.




Stainless match-quality barrels have a nasty habit of producing significantly higher pressures / MVs after 150-250 rounds down them, even after a careful running-in exercise. Some barrels seem to avoid this fate; others suffer badly. As part of a Hodgdon VarGet / H4895 alternatives exercise I'm running using 223 with the 77gn SMK, I recently remeasured my baseline MVs for the two 'control' powders as their original readings came from a new barrel with 65-120 rounds down it. The VarGet load saw an MV increase from 2,935 to 3,000 fps MV, but unfortunately I had to use a different VarGet lot and that likely accounted for at least some of the change. H4895 using the same lot as the original test saw 2,975 fps rise to 3,015 with all components the same as before. Both increases would have needed significant pressure increases. This phenomenon is being increasingly commented on in target shooting forums, and I know one gunsmith who warns recipients of a newly rebarreled rifle not to load up to max immediately and to recheck MVs and groups at around the 200 rounds mark. (MVs were measured on a Labradar, so should be reliable.)




Ow! That made me wince! Three was two examples too many - ie when that happens, not a single additional cartridge from that lot should be fired. I don't want to sound 'preachy' on this, but well remember a fellow shooter working loads up in batches of five many years ago. Something went disastrously wrong and he exited the range refusing to admit anything had happened or explain how he had a cut eyebrow with blood running down his face. He did admit to his best shooting friend that he knew his top load was OTT from the primer condition and hard bolt opening, but thought he'd 'get away with it' firing the other four off and avoid pulling them at home. He did get away with it for three further shots; the final one saw a case failure that blew the extractor off and out and that was likely what hit him. Half, three-quarters lower strike and it would have been a major injury and lost eye.

I am curious about the stainless barrels and pressure rising. Not that I doubt you but the why this happens I have some theory and am interested in your view.