Velocity swings

[Davros]

Hi All,

I am new to reloading and have been in the process of developing loads for my .243 and 6.5CM. I have been able to get good results with both (sub 0.5MOA @ 100yrds) The issue I am seeing is that even though the group sizes are good on paper the changes in velocity I see on my Alpha Master Chrony can be as much as 100fps. I am measuring my charges with an RCBS Chargemaster lite, the .243 has a forster FL sizing die and the 6.5 has a L E Wilson FL bushing sizing die(.290 bushing). I am using PPI cases in the .243 and Lapua in 6.5CM

Case prep for both goes:

Wet tumble w/SS pins, 1/4tspn citric acid anhydrous & splash of washing up liquid for 3-4hrs depending how they look, they will come out spotless
Washed in a rinse aid/water mix (roughly a healthy squirt into 5L of water)
Dried in a dehydrator for about 3 hrs @ 70C (probs overkill but I'd rather not risk any rust/damp when loading)
K&M primer pocket tool
Sized
Trimmed using a Lee case length gauge/cutter, chamferred & deburred with a hornady tool
Primed on the Lee bench primer, I aim for between 0.005" & 0.010" depth
Charged
Seated using Lee seating die in .243 & Forster micrometer seating die in 6.5CM - to within 0.001" variation in CBTO according to the Moore & Wright callipers with hornady LNL bullet comparator set

What are the causes of velocity swings like the ones I am experiencing and should I be worried about accuracy at ranges further than the tested 100yrds?

Thanks in advance,
David

 

[Liveonce]

blimey when did reloading become so technical, just get out shoot them 1/2MOA at 100yards is more than adequate in the real world I would say

 

[Davros]

It is more than adequate for deer at the ranges I will be taking them at but I'm a bit of a perfectionist and now Ive started down the path of creating something that is more accurate in my rifles I would like to tweak these developments and try to produce the best groups my rifles are able to shoot

 

[Liveonce]

It is more than adequate for deer at the ranges I will be taking them at but I'm a bit of a perfectionist and now Ive started down the path of creating something that is more accurate in my rifles I would like to tweak these developments and try to produce the best groups my rifles are able to shoot

Can become all consuming, got the t-shirt, enjoy the Journey

 

[gixer1]

Could be neck tension - has your brass all been fired the same number of times? Some people will anneal after around 4-5 firings.

How are you measuring the completed rounds? Is it OAL or Ogive?

Regards,
Gixer

 

[Davros]

My first thought was neck tension, I made a post about neck turning using a Hornady LNL neck turner and Fox Tales suggested I asked about other possible causes prior to buying the gear to do it.

All cases are fired the same number of times at the point of each test.

I'd rather not get into annealing if possible, I've heard its difficult to be precise when doing them by hand (drill / propane torch) & I don't have the money for a fancy machine!

Length measurements are CBTO (Cartridge Base To Ogive)

Regards,
David

 

[Rusty Gate]

Hi All,

I am new to reloading and have been in the process of developing loads for my .243 and 6.5CM. I have been able to get good results with both (sub 0.5MOA @ 100yrds) The issue I am seeing is that even though the group sizes are good on paper the changes in velocity I see on my Alpha Master Chrony can be as much as 100fps. I am measuring my charges with an RCBS Chargemaster lite, the .243 has a forster FL sizing die and the 6.5 has a L E Wilson FL bushing sizing die(.290 bushing). I am using PPI cases in the .243 and Lapua in 6.5CM

Case prep for both goes:

Wet tumble w/SS pins, 1/4tspn citric acid anhydrous & splash of washing up liquid for 3-4hrs depending how they look, they will come out spotless
Washed in a rinse aid/water mix (roughly a healthy squirt into 5L of water)
Dried in a dehydrator for about 3 hrs @ 70C (probs overkill but I'd rather not risk any rust/damp when loading)
K&M primer pocket tool
Sized
Trimmed using a Lee case length gauge/cutter, chamferred & deburred with a hornady tool
Primed on the Lee bench primer, I aim for between 0.005" & 0.010" depth
Charged
Seated using Lee seating die in .243 & Forster micrometer seating die in 6.5CM - to within 0.001" variation in CBTO according to the Moore & Wright callipers with hornady LNL bullet comparator set

What are the causes of velocity swings like the ones I am experiencing and should I be worried about accuracy at ranges further than the tested 100yrds?

Thanks in advance,
David

Get yourself a Sinclair Exoander Die & calibre mandrel, run it through after resizing

 

[Utectok]

Get a magneto speed or labradar to start with as optical chronos often are random number generators.
Also it’s very possible it’s just a rubbish node and ES of 50-60fps is normal for some pretty average load. 100fps is unusual but see above

 

[Lancaster]

What powder are you using and what % case fill does it give?

 

[Lateral]

Hi All,

I am new to reloading and have been in the process of developing loads for my .243 and 6.5CM. I have been able to get good results with both (sub 0.5MOA @ 100yrds) The issue I am seeing is that even though the group sizes are good on paper the changes in velocity I see on my Alpha Master Chrony can be as much as 100fps. I am measuring my charges with an RCBS Chargemaster lite, the .243 has a forster FL sizing die and the 6.5 has a L E Wilson FL bushing sizing die(.290 bushing). I am using PPI cases in the .243 and Lapua in 6.5CM

Case prep for both goes:

Wet tumble w/SS pins, 1/4tspn citric acid anhydrous & splash of washing up liquid for 3-4hrs depending how they look, they will come out spotless
Washed in a rinse aid/water mix (roughly a healthy squirt into 5L of water)
Dried in a dehydrator for about 3 hrs @ 70C (probs overkill but I'd rather not risk any rust/damp when loading)
K&M primer pocket tool
Sized
Trimmed using a Lee case length gauge/cutter, chamferred & deburred with a hornady tool
Primed on the Lee bench primer, I aim for between 0.005" & 0.010" depth
Charged
Seated using Lee seating die in .243 & Forster micrometer seating die in 6.5CM - to within 0.001" variation in CBTO according to the Moore & Wright callipers with hornady LNL bullet comparator set

What are the causes of velocity swings like the ones I am experiencing and should I be worried about accuracy at ranges further than the tested 100yrds?

Thanks in advance,
David

You still have numerous variables, none of which are particularly important, given you're getting sub 1/2" groups, good enough for further than you are likely to hunt.

Variables:

1) PPU case volume. I've been reloading some Geco 9.3x62, because it's common to lose cases when driven hunting, and it's less upsetting, than losing Lapua
The case weights vary by more than 5 grains, lowest, to highest. This effects the case volume sufficiently, to influence velocity.

2) I use a Chargemaster Lite. It's great, but, I also check each powder throw on a very accurate scale. No need to for my driven boar loads, but it's habit. Depending on powder, it can be +/- .16gn. In isolation, not a lot, but added to case volume, actual neck tension, on cheap, multi fired brass (do you anneal it ?) it can all add up.

3) In my experience, "Chrony's" tend to be optimistic ! Beg, steal, or borrow a Magneto Speed, or Labradar


There are people out there, who would kill for 1/2" groups !

 

[User00044]

Don't be afraid of giving annealing a go . Perhaps just try 10 cases . I believe it was Alantoo who wrote an excellent explanation using pure soap as an indicator , certainly worth a search .
I found excessively clean cases necks also gave me some issues, might be worth trying graphite in the necks, again perhaps just 10.
Consistency is key.

 

[Liveonce]

Agree with fox tales, annealing is beneficial to case life and consistent ammunition, more so than making it look shiny and clean, which I worry a lot less about.

 

[User00044]

I really thought you'd get more responses , oh well.

Some valid questions have already been asked , powder / primer choice , case fill % , number of firings and of course possibly just a poor node .
It is possible that some of your issues are a result of inconsistent neck tension , remember that the internal neck sizing in a standard die is set by the expander ball and this can be measured . If your cases have work hardened it will also affect obturation .
How did you decide on the .290 bushing for the 6.5 CM and what is your calculated neck tension it's worth noting that this sort of die will push inconsistencies inwards resulting in possible concentricity issues ?
Accuracy, when weighing powder . I have moved away from my Lyman Gen 6 and now use a beam scale and target master which gives better consistency.
Inconsistent case volume , less likely with Lapua than PPU.
Even allowing a round to warm in the chamber can have an effect , particularly with temperature sensitive powders .
I found issues with excessively clean necks and found an article or two referring to this as cold welding (albeit incorrectly) .
It's worth noting that the 243 is not an easy cartridge to tune for ES . Of course as Lateral points out could just be the chrono.

Welcome to Hell .

 

[Utectok]

Ohh and get some decent brass you won’t regret it. Anneal fl size and trim carefully and deburr flash holes

 

[3.5mag]

As mentioned above optical chrono's can be inaccurate/inconsistent depending upon ambient light & keeping your barrel in a level horizontal plane in relation to the chrono sensors.

 

[Sharpie]

Point one. The OP is claiming sub-0.5MOA tested at 100 yards, using approx. 1/4" projectiles.

I.e. they must consistently all at least cloverleaf, overlap or all go through the same hole. I'd like to see some of those targets. Many would be quite happy with that. Even just to get one such target to show, after rather more not shown, or excused with e.g. "I pulled that one, it was a windy day, the dog ate my homework so I don't have all the details etc."

He seems to have a reloading equipment list including reputable sizing dies and an adequate automatic powder dispenser.

But is now worried that he is seeing an ES of 100 fps.

If that is correct, then the theoretical impact of that on e.g. vertical dispersion is readily estimated with plenty of online calculators etc. And, I'd suggest, might be minor.

If correct, causes could me many and varied. Powder dispense variation. Case internal volume variation. Primer and powder variations. Case manufacture quality variations. Bullet manufacture quality variations. Batch to batch variations. Measurement technique and instrument errors. Day of the week, month of the year, is the wind in the East ? Temperature (a big one). Case conditioning techniques. Appropriate choice of neck bushing size, etc. etc. Nevermind primer pocket uniformity, flash hole uniformity, internal flash hole deburring, primer seating FUD, concentricity, there are tools for all of that, to improve , and others to measure. And so many other things, some as yet uninvented, or not yet brought to market.

Shiny cases obviously add to accuracy, wet tumble with SS pins, clearly that's going to make a difference, stands to reason. Must be better than Ultrasonic, the previous latest greatest idea. Oh really ? So pretty. But exactly just as worn out by use as any other case, nowadays probably the least expensive consumable of a round, on a par with the primer. But some can't bear to part with shiny brass, even when by all objective standards, it's only fit for scrap.

Just because you can measure something to x decimal places, doesn't mean it is of much practical relevance. This works both ways. Newer chronos can bamboozle you with data, claim to measure precisely every time to better than 1fps, can make you feel bad and fret about e.g. whether getting your ES below 10 fps is the starting point of anything useful.

Likewise powder throwing. Punch in a number, push a button, use it. Except that interested folk may also weigh again on their better digital scales or beam ones, and end up just using the automatic things to throw light, then they trickle up afterwards precisely. Or use e.g. Lee scoops or basic powder thrower for the initial under charge, then onto their good milligram or better digital scales, or decent balance beam, then finish off with the trickler. Just as fast, with a thought-through workflow.

I'd say that, at this stage, continuing to test at only 100 yards will not help discriminate further subtle details and interactions, he is already clearly beyond that stage of refinement.

Neck tension is an obvious point of call to look at, but the chap seems averse to even having a go at fairly well proven entry-level DIY annealing methods. Thinking that it is necessary to have an automatic machine to even get started. He is quite wrong about that.

As with many things reloading related, there is a spectrum of what is necessary, what is better, what cannot be easily done with tools already to hand, how well the user has the mechanical sympathy to use them (improvised or specialist dedicated reloader kit) and what is frivolity, fashion, marketing, or just BS.

Chronoing is a case in point. Some get so fixated on them that seemingly every shot not recorded on e.g. a Magnetospeed or a LabRadar is a shot wasted, and fret over gaps in their records without. And fret over their ES and SDs, whether or not they are perfectly good enough, Still there are always different powders or projectiles to try out, and soon enough a new barrel needed, to start all over again.

 

[Sharpie]

As mentioned above optical chrono's can be inaccurate/inconsistent depending upon ambient light & keeping your barrel in a level horizontal plane in relation to the chrono sensors.

Just as they can be extremely accurate and consistent when used understanding how they work. As with most tools, you generally get what you pay for, but to get the best from them might need some thought and knowledge of what they can and cannot do. Of course, if you just want to attract attention to yourself, there are plenty of experts on e.g. youtube happy to show how not to use such things and make them look bad. Not so many showing how to use them properly and get the best out of them.

That said, the Chrony Alpha Master, as used by the OP, would not be my first choice nowadays. ISTR that the original manufacturers went out of business quite a while ago, but it seems someone has picked up the pieces and they are being made again. Same thing or maybe improved, I would not know.

 

[3.5mag]

Attract attention to myself???? Where the hell do get that from?
Anyway, like a previous poster I was simply trying to give a possible explanation based upon my own experience with such chrono's AND having seen plenty of YouTube vids with incorrect use of said chrono.

 

[Utectok]

For what it’s worth I had a load that was grouping 1/2” at 100m (bullet centre to bullet center so not necessarily touching bullet groups) and had an ES of 70 or so and it had a fair bit of vertical at 370m which is not surprising. I had lost the powder node when adjusting the bullet seating depth and settled after some extra trials for a slightly worse 100m group but an es of 11 and a 4” group at 370m

 

[Davros]

I must admit I have not been impressed with the consistency of the Alpha chrony, it will sometimes refuse to register 5-6 shots then all of a sudden record 30 in a row, before it stops again. All without moving firing position or chrony targets arranged as below @100yrds. I do have a friend who has a LabRadar so I may ask if I can put a test of rounds by it & see how the recordings compare to the alpha chrony. He tells me it rarely fails to record.

My 1/2" groups have been measured bullet centre to centre (is this not the done thing?)

I have found N150 to be most harmonically stable in my CM and Superperformance performed best in my 243 (definately a harder calibre to tune) I use Large CCI primers for both. I have not worked out case volume % used. I pick a starting point and increase in 0.3gr increments. I'm sure it can be worked out, unfortunately at this moment in time I am just too busy with work.

The bushing die was the main reason I was looking into neck turning. I chose the .290 as the lapua brass I measured averaged a 0.014" neck thicknes (290-28=262 ie 0.002" tension) If I did start to turn necks I would require a tighter bushing but I was aiming for either a 0.003" or 0.002" tension. However due to inconsistencies in neck thickness the actual tension on the bullet head will depend on neck thickness consistency, hence the idea of turning to increase consistency.

I will try and find the info written by Alantoo although if you have a link that would be appreciated. I had seen a youtube video by (I think) Eric Cortina which in summary stated that poor annealing is worse than not annealing at all but you have peaked my interest

Here is my latest powder test using N150 going up in 0.3gr increments



I have tried to answer most of the points previously mentioned, Im sorry if i missed any out - just finished a 13hr shift on site & am back in tomorrow morning.

Thank you all for your input so far. I find the theory for this process just as enjoyable as the practical.

Regards
David