7.62X39 case length trimming

[ksjayhawk]

Hey guys. Been reloading for a few decades now. Thought I'd try my hand at some 7.62x39. I've noticed that after resizing the brass. That very Few (maybe 1 in 30?) actually need to be trimmed down to 1.528". I've resized about 25 so far. And I can't seem to get any brass trimmings. I take the digital calipers to them and they almost all come in 1.527" or a smidge under already. The couple I actually got to trim were 1.530. So not much at all. Is it due to the cartridge being such a low pressure round that there's not much expansion??


thanks.
eric

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[DizzyJ]

What was the length before firing?

 

[Certaindeaf]

They probably didn't need trimming because they didn't need trimming.

 

[fstdraw]

1.518 is the proper trim to length I believe.

 

[ksjayhawk]

Actually all 3 of my reloading manuals have the case length at 1.528". Sorry dizzy. As to the length before firing. They were all factory ammo brass. I don't take the time to measure factory brass before the range. I just load them in the mag and shoot them. Then worry about processing after the range time.

 

[ma96782]

For me, speaking of reloading "my rifle caliber cases".....
I look at trimming for the first time as.....
An opportunity.

To get all of the brass (from that lot) trimmed to the "same length".

Yeah, it could/might just help.....with getting the bullets to crimp at a "uniform length/spot". And, it might just maybe help with accuracy too.

Uniformity.

Aloha, Mark

 

[po18guy]

They probably didn't need trimming because they didn't need trimming.

 

[ksjayhawk]

I've done some further reloading forum research. And it turns out that specifically the 7.62x39 is such a low pressure round that the brass grows negligibly if at all. Everyone with 7.62x39 reloading experience seems to say the same thing that if it needs trimming, then trim it. that will probably be the only time you trim it For the remainder of its useful reloading lifespan. After 5-6 reloads, the case will crack ending the useful life of the case before it will need trimming again if at all. I'm just so used to working with .308, 30-06, and 300WM and trimming them all significantly after firing them the 1st time. It was just surprising that it's not as significant a requirement for 7.62x39.

 

[fstdraw]

I have yet to trim any of my 7.62x39 cases. I reload steel and brass (Berdan and Boxer), neither seems to need trimming. I can get 3 loadings from steel if I can find them and more from brass.

762 is fun to shoot as well.

 

[ksjayhawk]

Absolutely. i have several 7.62x39 spitters. but Ive accumutated so much brass reloadable. I thought it'd be practical to get good at reloading them. Most guys have stated that they've 3/4" to 1" off their groups out of their SKS's With their own reloads. I have several boxes of projectiles to play with as well.