Primer initiated premature bullet jump

358156 hp

Well-Known Member
Below is a copy of an Army testing board report on primer initiated bullet jump in 5.56 & 7.62 military ammo. I think we've all known of the potential for this, but could/would the effects of the primer firing be mitigated or at least modulated by the type of powder used? Could this be having an effect on the old "extruded powders tend to be more accurate" theories?


Well-Known Member
Ok, mind blown. Ric and Brad aren't members of AR.

Great find there, filed under "suspicions confirmed".

Primer pop is why I use Federal LP in the .44 Magnum with 2400. Not so bad with faster powders. Also why the small-primer .45 ACP brass is such a good idea.


High Steppes of Eastern Washington
Ian, I have too many interest to belong to another board. You guys are it for me. HP, second link worked.

I don't know if I am reading something else into this, but I suspected something like this. 100% load density gives good chronograph data, but do not equal good accuracy. Figures 11 and 12 seem to suggest that having compressible empty space in the case allows for smoother acceleration and maybe better accuracy?