Thread: Reloading subsonic 7.62x39

I've tried it.

Picked up a box of 150gr and 180gr Speer .303 projectiles. The 180's wouldn't stabilise in my rifle - so I'd recommend checking your twist rate and using the JBM stability calculator before buying anything that long/heavy. With 150's and Trail Boss, velocity was quite erratic, and the average was quite low. I was lucky I didn't get a squib. It could have been my shitty loading practices (I was relatively new to it, at the time). I tried AR2205 and velocity was much more consistent - accuracy was even quite "good" - but with the slower burning powder, it was noticeably louder, and cases came out very dirty, indicating chamber pressure was so low that case necks weren't sealing. The odd bit of unburned powder indicated I wasn't getting proper ignition too. I stopped messing around with subs in that rifle at this point.

Later experiment with a different x39 rifle, I tried AP100 to make a reduced load that would just barely cycle the action. It worked extremely well. ~1800fps with a 123gr, gently coughing out spent cases in perfect condition. The burn rate of the powder is faster than AR2205 and it's much easier to ignite, being a flake powder that's better suited for shotguns than rifles. Turns out it's an excellent powder for subs too, especially in cases where you don't have enough capacity to get your desired bullet up to ~1050fps with a suitable amount of Trail Boss. I now use it in 300 blackout and 44 mag.

I've also tried the cast bullets made by @shooternz. Those would be worth investigating if you need projectiles to expand (the Speers are tough and would pencil through anything). They're soft lead which is easier to drive down the barrel (more fps per grain of powder) which is handy if case capacity might otherwise be a limiting factor with similarly weighted jacketed bullets. And they'll stabilise in anything. Just be aware that you'll have to buy a flaring die - and I've not been able to seat them without significant deformation of the noses.

Would help to know what your intended purpose is before sharing any load data.