I started crimping the cases of my 375 H&H magnum loads last week. The rounds are more accurate and the point of impact has shifted. Has anyone else had this happen? I had to shorten the AOL of the rounds to crimp them and I was wondering if it was the longer distance to the lands that has affected the accuracy and the point of impact rather than the crimping?

Thanks.

Sounds like you reduced the effective case capacity and increased pressure a bit, which will account for a shift in POI.

Crimping often aids accuracy as you produce a more concentric round. It also improves the burn efficiency and may indeed slightly increase pressure. I'll bet if you chrono the load, your SD will be decreased. I always crimp cartridges designed for dangerous game to prevent bullet set-back in the magazine.-Rob

Saeed himself did a very interesting study on the effects of crimping and he found considerable correlation between improved accuracy. I forget where on his site I read this, but it was good.

I prefer the so called "Factory Crimp" dies from Lee if I can get them as they pretty well eliminate the risk of shoulder set-back and I think just do a cleaner job of crimping.

This is an interesting question that I am about to investigate myself. I have been developing loads for a 9.3x74R double rifle and, frankly, it has been a difficult road until I tried RWS TUG projectiles and then suddenly I obtained great accuracy. I am going to try some experiments to determine the reason for this but I strongly suspect it is because I can crimp the RWS projectiles while I haven't been able to crimp the Woodleighs or Speers.

If anyone has any light to shed on this I would be pleased to hear about it.

I rarely used any crimping for rifles until I began laoding for 375 and up. I now crimp my 416 Rem religously with a lee crimping die. The accuracy has improved and I don't want to take chances with non crimped bullets in the magazine when shooting. I have developed a load using Barnes 400gr "X" bullets and 400gr solids that will shoot all shots within 1.5" @100yds, sometimes less and adequate velocity. I don't get that good of a result without the crimp.It's also very easy to do compared with using the seating die. They can be purchased very cheap. You can even order them directly from Lee. I should add that I had them make one for the 416 Rigby(not a stock item) too with the same results.

I crimp only to resist setback in heavy recoiling rifles and not even then for the top loaded soft point that never sees the magazine. I may also crimp lightly to ensure slick function at feeding.

Should a particular die fail to produce the crimp shape I want, I use a Lee collet crimp when available, which gives a gentle rolled in result.

At times, crimping or not crimping will aid you in getting softs and solids to group more closely and/or fine tune your double rifle regulation.

IT is my feeling that crimping can help OR hurt accuracy in a given rifle but that it hurts far more often than it helps. Each rifle is different and none of us can inside and outside bevel our brass with enough precision to say that crimping results in a more concentric round. In other words, the amount of material encompassed by the crimp varies from round to round, no matter who is doing the beveling. No guarantees either way.