Subsonic 7.62x39 project

Flashpoint · Feb 22, 2015

I'm attempting to develop some subsonic loads for 7.62x39. I'm using Hornady 208gr Amax and IMR 4227. When I seat the bullet in far enough to fit in the magazine the neck is into the ogive of the bullet. My dies came with both .310 and .308 sizing "shafts" and I'm using the .308 one, but as you can see since it's well into the ogive it's not crimping all the way.

One problem I see immediately is that since it is not well crimped the bullets in the magazine may set back further under recoil. What are some other possible problems that this can cause?

I'm using data for 300BLK for this powder and bullet which called for 9.4gr of IMR 4227. My plan is to load some 9.0, 9.2, etc. up to 10gr and chrono them. At first I was concerned about load density but just from looking at the amount of powder vs bullet in the case it's got to be 70% or better. I'm also not worried about OAL because the slim profile of the bullet will cause it to not engage the rifling until after the standard Tula round would, so no worries about pressure there.

Any suggestions on what to do about the ogive of these bullets? Maybe try a Lee Factory Crimp Die? I want to use the heaviest I can. My barrel is a 9.5" twist.

Std Tula round on the right for comparison.

joker00 · Feb 22, 2015

this may be not the answer. maybe not even right at all but could you trim the case a little to make sure the neck can be crimped? I'm sure someone on here has ran into this and can shed some light

Catfish · Feb 22, 2015

That's the first thing I thought of too. Take a little off and make your own 7.62x38r (r for ******* instead of Russian) then make a few dummy rounds to test feeding and check for setback.

LeadFarmer · Feb 22, 2015

Turn the bullet around backwards and use a 70% case capacity charge of trailboss.
That's my standard reply as cookie cutter as "eat better and exersise".

Flashpoint · Feb 22, 2015

I see how they got around this with 300blk, they cut the case way back. Compared side by side the case neck extends only up to where the neck starts on the x39. I may have to look into a x38r lol! Or maybe I just have to drop down to a lighter shorter bullet, but I'd like to avoid that if possible. What about trying to crimp it better where it is with a FCD? Could that cause pressure issues?

I've heard about turning the bullets around before, and I have trail boss. I doubt I could get enough trail boss in that case to get the velocities where I would want them. Heck it took most of a .308 case to push a 178gr close to the speed of sound IIRC. Also if one plans to push the distance limits of sub shooting like I am it would kill the BC of the bullet.

Thanks for the replies!

Flashpoint · Feb 23, 2015

So today I chronoed my first batch of rounds.. I loaded 3 each from 9gr up to 10gr in .2gr increments, for a total of 18 rounds. Velocities averaged from approximately 650fps at 9gr to 850fps at 10gr. None of them cycled the action with the suppressor installed. Extreme spread at each charge weight was horrible, around 10-15%. I'm not sure if it's due to low charge weight/case density, or the poor crimping. I do know that the charge was low so next I'm loading from 10 to 11gr and we'll see what happens then. Stay tuned.

Testing platform:

Wahoo95 · Feb 23, 2015

You'll most likely need over 1000fps to get it to cycle. Try tracking down some VV N160 powder...I saw some at the fun show yesterday.

ak47 subsonic cycling semi auto:

Subsonic 7.62x39 project

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