Reloading Subsonic 7.62x39

[beerslurpy]

I am in the midst of having a reflex can made for my tacticool AK. I think it has great potential as a "poor-man's 300 whisper" that can go back to being a quiet assault rifle with only a mag change. A 180 or 200 grain RN at around 950 to 1050 fps will hit pretty hard I imagine.

I noticed that there are subsonic ammo makers for this cartridge, but they all use 308 caliber bullets for the 7.62x39 M4 carbines. Which isnt really a great match with my barrel, which expects .311.

So anyway, I did some reading and some calculating and I think that with 303 british RNs and the AKs 9.6" twist rate I should be able to easily make some ammo that is stable deep into the subsonic range. The problem is that I havent had any luck finding actual recipes that say "this many grains of red dot will push a 180 grain projectil at 950fps." As long as I dont leave the case more than half empty, is it safe to just keep taking powder away from a proven load until I hit the appropriately low velocity?

Pointers? I am not really an experienced handloader as I did not have the misfortune of living in the bad old days when ammo was hard to find.

 

[Bigfoot]

I'm sure you know that reduced loads of slow powder can cause a secondary combustion. SR4759, XMR5744 and H4895 at over 60% are the prefered powders for reduced loads. I'm sure that there are others too. This page lists some pistol powders.

http://members.shaw.ca/cronhelm/762Page.html

http://www.quarterbore.net/forums/forumdisplay.php?f=27

Some people have found better accuracy with the Russian case over the Whisper.

 

[AndyC]

With a reduced load, more surface-area of the propellant is exposed to the primer's flame when the case is horizontal - the net effect can mean dangerously high pressures.

Think of a bottle of water turned on its side - the bottle is the cartridge-case and the water is the propellant. If the bottle is almost full when you lay it flat on its side (as in a cartridge when chambered) not much surface area is exposed at once to any flame from the primer at the rear. If the bottle is half-full, the entire upper surface of the water (propellant) is exposed to the flame so more propellant burns in the same amount of time - this obviously means a faster pressure-peak which can explode the barrel/action.

I've used cotton wool as a filler before to keep the propellant firmly wedged against the bottom of the case before seating and crimping the bullet in place - you can make up your own fillers. The weapon won't cycle if you go too low in powder-weight, of course - careful trial and error will be needed if you don't want to cycle the action by hand for each shot.

Of course, if you already know all this, ignore my ramblings and do your own thing

 

[Cosmoline]

Those problems are MUCH more significant when you're trying to rig up a reduced load for the .45-70 or .45 Colt. For the x39, if you put a 200 grain slug in there even a few grains of handgun powder will be pretty tight. I think you'll run the risk of causing more problems by putting filler in there too. I'm working up some heavy bullet loads for the x39 and discussing results in the handloading forum. But I'm not going for a whisper load. Rather, I'm pushing the cartridge to its limits at the 170 grain range. For a true whisper you want a big honking slug backed by a small charge of powder. I have no idea how that would function with an AK. Frankly I've waited until I have a CZ before doing any testing on the x39. If you look on this forum you'll find the description and photos of a blown up SKS using heavy handloads. IMHO it's one case where you must trust in Mauser.

 

[The Scandinavian]

Some interesting stuff here

Three pages of interesting reading for you -
How to Handload Subsonic Rifle Cartridges, by the late P.T. Kekkonen:

http://guns.connect.fi/gow/arcane1.html
http://guns.connect.fi/gow/arcane2.html
http://guns.connect.fi/gow/arcane3.html

 

[Reed1911]

Look here http://www.accuratereloading.com/76239.html

 

[Boom-stick]

There's a lot of guys over here using 3.5grns of bullseye in .308 win bolt guns as a close range fox loads or gallery rifle loads. Would this tranlate well to the 7.62x39?
I've read the links and there's not quite the answer there I'm looking for.

My local range is a handgun range and only rated for stuff going 700-900fps or less (unless its .22 lr) and no jacketed rounds, I can cast lead heads so that not a problem, I just need to find a load that will allow me to use an AK there.

 

[jerkface11]

Try the .308 bullets you may be shocked at the accuracy.

 

[Boom-stick]

Try the .308 bullets you may be shocked at the accuracy.

Thanks,

I still need to know how many ???grns of powder to put in the case without needing reconstructive facial surgery.

 

[Bigfoot]

Read this thread on the 300 Whisper forum Boom-Stick, loads are listed. http://www.quarterbore.net/forums/showthread.php?t=512