Why doesn't the Lapua match grade .222 Rem. brass have the small flashhole?

[South Pender]

Purchased 100 Lapua cases headstamped "Lapua Match 222 Rem", and noticed that the flashholes were the standard larger size (.083"?). I was surprised by this. Wouldn't the smaller flashhole found in the PPCs work well in the Deuce too?

 

[Uncle Ed]

Because its only loaded to 46,000 cup or 50,000 psi.

 

[South Pender]

This would seem to suggest that the small flash hole size (~.060") was introduced to contain higher-than-normal pressures. I had thought that its purpose was to produce a different flash into the powder than found with the standard flash hole size--perhaps extending further up into the case.

Because its only loaded to 46,000 cup or 50,000 psi.

This would seem to suggest that the small flash hole size (~.060") was introduced to contain higher-than-normal pressures. I had thought that its purpose was to produce a different flash into the powder than found with the standard flash hole size--perhaps extending further up into the case.

 

[Laurie]

The triple-two is primarily a sporting cartridge these days and 100% reliable ignition takes priority. This is particularly so in Lapua's home region Scandinavia where the 222 is widely used for winter bird stalking. Head-shooting a grouse in a Finnish January can see use in some pretty low temperatures.

The small flash-hole usually reduces ES values, but also reduces the flame front making it less effective under cold conditions especially with some hard to ignite ball powders.

 

[Ned Ludd]

FWIW - Alpha Munitions also has the larger flash-hole on some of their SRP brass. A while back, I asked them about it. You may find their reply of interest:

First off thank you for purchasing our 308 SRP brass, and for the question concerning our small primer pocket large flash hole setup. There has been a lot of debate back and forth concerning small vs large flash holes, and most of it is just that, debate. It is hard to find any kind of confirmed study. This answer may get a little long, but its a question deserving of such an answer.

First, we have only performed testing on larger volume 308 cases, being the 6.5 creedmoor, 260 rem. and 308 win. There is a lot of history from benchrest shooters who have looked at flash hole size within the PPC family. The results of each case (ppc vs 308) individually cannot be assumed true for the other size cases. Due to gas pressure being highly sensitive to volume (PV=znRT, ideal gas law), and many other factors, it is not valid to assume the results for one particular case must transfer to another case. That said, I'll discuss more what we have seen and found.

Lets hit some background first. People speak of the "jet affect" which was assumed in Percussion Primers, Design Requirements by E.R. Lake, 1970 where he states "as the size of the flash hole is decreased, then the pressure of the [primer] products and the length of their "spit" is increased". Simply put, the smaller the flash hole the greater the length of the jet the primer creates. Going through this report there is zero data backing up the jet affect for our specific application (rifle ammo). A further study, most popular and known in the shoooting industry was performed by German Salazar, 2011 Large vs. Small Flash Hole Test, which presents photographic results which may contradict the "jet affect". Salazar shows images of a large flash hole primer pocket appearing to visually produce more "spit" or "flash" in comparison to the small flash hole. Again, this is all visual results with no quantitative test data.

The reason I wanted to hit on the past research or common knowledge in the shooting industry is that people believe this stuff and speak like it is the 100% undeniable truth, when there is no true data to back it up. We started looking into the large vs small flash holes and have shown the affects of the flash hole on the end result, being the consistency of velocity. Our tests have taken identical cases, except for the flash hole size, and observed the performance characteristics of both. There is a lot of detail I could go into for the setup, but I'll save that for the technical article. We first found a velocity node to shoot well then loaded the same load into the test cases. These were then shot out of the same gun, and recorded using the same chrono (lab radar setup).

In standard conditions we found to have slightly better results (velocity ES and SD) with the small primer pocket large flash hole setup, now is it a huge difference that would blow everyone away, no. However, testing at extreme low temp conditions we did show the velocity ES difference between the large and small flash holes opens wider.

It is my opinion that there is a balance of both primer and flash hole size to produce the best velocity ES. I think for optimal results you want to use the smallest primer possible which effectively ignites the powder charge. There is too much variance in primer ignition pressures that, I think, leads to much of the pressure variance in firing, consequently affecting the bullet velocities. It is possible (my THEORY.. just a theory...) that the jet affect could actually worsen the inconsistencies of the primer ignition creating greater inconsistencies in the powder ignition.

Anyway, really appreciate the question and I hope this helps!

 

[Laurie]

In standard conditions we found to have slightly better results (velocity ES and SD) with the small primer pocket large flash hole setup, now is it a huge difference that would blow everyone away, no. However, testing at extreme low temp conditions we did show the velocity ES difference between the large and small flash holes opens wider.

My views (prejudices? ) exactly!

I'd throw in powder sensitivity as well. Small primer / flash-hole may give excellent results with some grades and poor with others. This gives rise to opposing views among shooters often at the extremes - useless and excellent. I've noticed such views on the forum for SP 243 Win brass already despite its newness and what must be limited numbers of users at this stage. One respected top US national shooter threw his out after seeing major velocity and ES issues with H1000; others are reporting excellent results with the same brass with Viht N160 and N165. (I've used SP / small flash-hole brass a lot with Viht N150, N160, and N165 with excellent results in temperatures between just above freezing to ~80*F in charges as high as 50gn in 308 'class' case sizes. N140 threw up doubts though in a cold weather 308 Win test and CFE223 didn't work at all in 308 despite reasonable temperatures - 48 slight hangfires and two complete misfires in 50 rounds!)

The primer model (perhaps even production lot too) becomes more important IMO and not just with the larger cartridges. I saw an example last year where a switch from F205s to Rem 7.5BRs, no other load changes, transformed a 6.5X47L custom tactical rifle's performance (for the better).

 

[South Pender]

Ned Ludd, thanks for your reply and the empirical evidence--immensely helpful! Empirical findings certainly beat theoretical assumptions and "folk wisdom." And, Laurie, thanks for your insights too. From all of this, it appears that other factors play a far greater role than flash hole size alone and that experimentation with different primers may be worth considering.