7.62x39 to Grendel - interesting side obseration.

[lazyengineer]

I've noticed that if one headstamp matches up 7.62x39 brass, the accuracy performance is actually quite good. Indeed, my best groups I've getting in Grendel so far, have been in FireForming PMC 7.62 cases using 90 TNT's. The rounds didn't even fill the chamber, since they were still 7.62 non-fireformed casings, yet I shot nearly half MOA - better than any other load I've ever shot.

I'm curious why that might be, and have two theories - that I'm putting out there to be laughed at.

1) My 7.62x39 load is on the mild-side, due to the variable nature of that brass dimensions (i.e. vastly different case vavolume depending on who made the brass). And maybe my gun and this round likes it more mild.

2) The recent look I've had into the SAAMI chambering of Grendel, where the neck is purposly cut bigger than it really needs to be. 7.62x39 brass is going to have a thicker neck, and fill up that space more fully, than original 6.5 Grendel brass. I'm wondering if that is a factor in the inherent accuracy improvement I'm seeing as well?

Obviously, the best way to ttest this, is to run my 7.62x39 spec Grendel load in true Grendel brass side-by-side, and see how they perform relative to each other. Which I think I may well do!

[Dt219]

Now that does sound interesting GO FOR IT !!

[rickt300]

I recently did some reforming 308 brass to 260 Remington. Necks are thick enough that after they are fired you can't run a bullet base into the neck. Typically there is .0012 to .0015 spring back of brass. I have even loaded brass without sizing it, excellent accuracy but can't magazine feed or at least don't trust the neck tension that much. Pressures are normal.

[LR1955]

I've noticed that if one headstamp matches up 7.62x39 brass, the accuracy performance is actually quite good. Indeed, my best groups I've getting in Grendel so far, have been in FireForming PMC 7.62 cases using 90 TNT's. The rounds didn't even fill the chamber, since they were still 7.62 non-fireformed casings, yet I shot nearly half MOA - better than any other load I've ever shot.

I'm curious why that might be, and have two theories - that I'm putting out there to be laughed at.

1) My 7.62x39 load is on the mild-side, due to the variable nature of that brass dimensions (i.e. vastly different case vavolume depending on who made the brass). And maybe my gun and this round likes it more mild.

2) The recent look I've had into the SAAMI chambering of Grendel, where the neck is purposly cut bigger than it really needs to be. 7.62x39 brass is going to have a thicker neck, and fill up that space more fully, than original 6.5 Grendel brass. I'm wondering if that is a factor in the inherent accuracy improvement I'm seeing as well?

Obviously, the best way to ttest this, is to run my 7.62x39 spec Grendel load in true Grendel brass side-by-side, and see how they perform relative to each other. Which I think I may well do!

LE:

It also says something about the value of annealing, polishing, primer pocket work, trimming and turning, weighing brass, etc. Maybe even cartridge run out.

LR-55

[Lemonaid]

LE, is your 7.62x39 converted cases large primer or small primer pockets? I have seen better accuracy in some of my 7.62x39 to 6ppc brass loads and think that using large rifle primers may be why.

[LR1955]

LE, is your 7.62x39 converted cases large primer or small primer pockets? I have seen better accuracy in some of my 7.62x39 to 6ppc brass loads and think that using large rifle primers may be why.

LA:

I stopped shooting 7.62 X 39 brass when I could get real Grendel brass so I can't recall if I noticed a difference. I had some small primer 7.62 X 39 brass but can't recall if they shot better or not.

With the lack of Grendel brass today I can see guys converting 7.62 X 39 brass once again. I personally have enough Grendel brass on hand and do not regret the thought that I don't have to deal with 7.62 X 39 brass again. Or 6 PPC opened up and blown out.

LR 55

[lazyengineer]

LE, is your 7.62x39 converted cases large primer or small primer pockets? I have seen better accuracy in some of my 7.62x39 to 6ppc brass loads and think that using large rifle primers may be why.

In my case - for the most part Large Primer. For a while there Hornady was making small primer brass, and the supply chain management bugged, me, because you no longer had an obvious tell on what brass was 7.62 origin, and what brass was obvious grendel (the large primer will always be the tell). So I think I just ran and discarded the small primed 7.62 small primed brass. Back when that was no big deal, just throwing stuff like that away....