In beginning my research into an SBR, I was wondering what the shortest practical length for the 7.62x39 Russian cartridge? I assume civilian AK rifles have 16" barrels, or barrel plus muzzle device equal 16+ inches. Is this caliber a good candidate for making/buying an SBR?
Shortest Practical Length for 7.62x39
- Thread starter DMW1116
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BreechFace
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- Mar 2, 2020
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Yes, 7.62x39 makes for pretty good ballistics down to 10”. Personally, I wouldn’t go shorter than that as one is giving up too much for any marginal difference in length under that.
I'd agree 10" would be a good balance especiallyif you're mostly shooting supers. I don't play with 7.62x39, I do have 8" and 10.5" 300 Blackouts. My drop off in velocity with especially with subs isn't much with supers it's more significant although even then it's no deal breaker. The x39 has more case capacity and works at a lower pressure so my SWAG would be it's drop off would be a bit more from 10 to 8 with supers.
Nice thing once you have a Form 1 SBR lower you're free to swap basically any upper you want onto it.
I have 2 lowers SBRed and another one braced and have 6 uppers I can move around.
adcoch1
Member
I've played with a 10.5" AK pistol, and that is about as short as you would want to go. The blast is significant, more than a 8" blackout. I think x39 is a pretty good sbr cartridge, but without some focused handloading it'll be pretty noisy and flashy any shorter than 10"
Specifically, I'm looking at a PSA KS-47 with a 10.5" barrel. That's the simplest version and I live and work within at least 2 of their stores. The available data for subsonic loads for many calibers is growing, and I'd like to try some to see if they'll run. This is a project that will be a while coming together though, and it's likely I'll just go 9mm instead for cost reasons. Still, it's good to have all the information.
someguy2800
Member
If you were going any shorter than 16" I personally would get a 300 blackout instead. I have a 10.5" 7.62x39 and a 300 blackout sbr also and the muzzle blast on the 7.62x39 one is ridiculous. That is kind of what I was going for with it though. The shorter and shorter the barrel, the smaller the performance gap between 7.62x39 and 300 blackout.
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