Accuracy, Small VS Large rifle primers

[R.W.Dale]

There are very few cartriges where you would have a choice between the two sizes of rifle primers but there are a few, so I wonder with all else being equal in small to medium capacity cartriges would one size primer be inheriantly accurate than the other size?

[Steve P]

Some of the 308 match brass came out with small rifle primers.  They were few and far between.    Some of the early BR brass had large rifle primer pockets,  but now almost all are small rifle primers.

The 6br, 7br, PPC rounds, and other match type rounds use small primers.

The Bower cartriges, the 308s, 30-06s, and other rounds used in long range matches from 500 meters and beyond usually have large rifle primers.

I don't know where the breakover point is in case capacity where you go from small primer to large, but from the info above, I think you can assume if a different primer was more accurate, you would find more brass available with a optional primer pockets.

Just my .02

Steve  

[Lone Star]

The .308 Match brass with small primer pockets was made for forming 7BR cases originally, but some guys started to use the case for full-length cartridges.  The .22 CHeetah was one such case (necked-down .308),  and it was claimed by the deveolpers and some owers that accuracy was slightly better with the small primer.  However, in cold temperatures varmint hunters found that ignition was sometimes spotty, and today most agree that the small primers belong on small capacity cases, just like they were originally designed for.

Cast bullet shooters often find that large pistol primers will give better accuracy than rifle primers due to the less viloent igniiton ( hot primers are not needed for the reduced charges of faster burning powder often used in CB matches).  I found that to be the case in several cartridges, particularly the .38-55 and .30-30.  Federal even was pursuaded to make a batch of small primer pocketed .30-30 cases, and CB users of these caes swore by them.  Again, a relatively small case with easy to ignite powders.

[R.W.Dale]

Interesting posts, I have not thought about using large pistol primers in leiu of large rifle. The reason I ask is that I've been trying wring as mutch accuracy as possible from my CZ527 in 7.62x39. Even though I get resonably good groups using LR primers the SD is really bad as well as primer setback and flow is completely inconcistent from shot to shot. All with start loads using .308 bullets in a .310 bore. Therefore I suspect that for lighting 24.0 grs of AA1680 a LR primer is just too darn hot. Correct me if I'm wrong but the only diffrenc between Large pistol and large rifle primers is that the pisrol will seat deeper into the case?

[Lone Star]

The LG pistol primers also have a thinner cup, so they will not contain as much pressure as a rifle primer without deforming.  I've used them up to ca. 45,000 CUP-level loads without problems though.