Subsonic 7.62x39 in SKS

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I Dont Care About You

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The other day I came across a box of .311" Hornady 255gr SubX bullets marketed for 7.62x39.

I asked the store what the hell people were doing with such a bullet in Canada as we only have the SKS to play with and I tried factory subsonic 7.62x39 in an SKS which failed miserably.

I was told that approximately 13gr of CFE BLK would cycle an SKS. Anyone tried such a loading?

I quick peruse through the Hodgdon Reloading Centre shows a whole bunch of subsonic loadings for the 7.62x39 with the 255gr SubX bullet.

CFE BLK 13.2gr - 1073 fps

The powders I have in inventory are:

5744 11.8gr - 1041 fps
H4198 12.8gr - 1067 fps
H322 14.5gr - 1063

I'd be willing to spend the dough on a box of the bullets if there was a reasonable chance these loads might actually cycle an SKS.
 
Nothing like downloading a supersonic cartridge with a mini bullet.

9 mm, 124 gr, at sub-sonic speeds, is probably a decent paper punch.

.30 calibre, 139 gr, at subsonic speeds, should also pierce that paper target.

But anything more important than paper, in the subsonic realm, should probably be fat and heavy.

Yes, I admit to a prejudice, developed over a half century ago.

It began with the subsonic loading of the .44 magnum, continued with the .44 spl, and has continued with the .45 ACP.

The Brits occasionally have a brilliant idea and the integrally suppressed SMLE, chambered in .45 ACP was a beaut!
 
I'm skeptical that: "approximately 13gr of CFE BLK will cycle an SKS."

You need three things to occur simultaneously:

1. the bullet's MV must be under about 1100 fps;
2. the pressure must be low enough so as to not cause damage, but high enough to reliably ignite; and
3. the gas produced must be of sufficient pressure and volume to cycle the action.

Typically when you're close, but not quite there (e.g. a bit fast), you can use progressively heavier bullets to lower the MV.

A compressed load of CFE BLK with a heavy bullet will likely saitisfy #1 and #2, but the volume of gas might be too small.

Then (when close to cycling the action) people tinker with lighter recoil springs and find that it won't then be able to pull a cartridge from the magazine and chamber it.

The only way to know is to try!

Besides CFE BLK, I'd also try a bit more of a but slower powder like 4198 and H322 - more gas volume at around the same pressure.
 
I Dont Care About You said:
The other day I came across a box of .311" Hornady 255gr SubX bullets marketed for 7.62x39.

I asked the store what the hell people were doing with such a bullet in Canada as we only have the SKS to play with and I tried factory subsonic 7.62x39 in an SKS which failed miserably.

I was told that approximately 13gr of CFE BLK would cycle an SKS. Anyone tried such a loading?

I quick peruse through the Hodgdon Reloading Centre shows a whole bunch of subsonic loadings for the 7.62x39 with the 255gr SubX bullet.

CFE BLK 13.2gr - 1073 fps

The powders I have in inventory are:

5744 11.8gr - 1041 fps
H4198 12.8gr - 1067 fps
H322 14.5gr - 1063

I'd be willing to spend the dough on a box of the bullets if there was a reasonable chance these loads might actually cycle an SKS.
Click to expand...

Quite a few years ago I played around with 180 bullets and Trailboss. I couldn't get the bolt to cycle and it essentially became a straight pull bolt action.

Lots of Canadians have bolt action 7.62x39 rifles and can some of them using these.

Heavier grain bullets do allow you to have more powder in the casing (increase pressure) while allowing you to get subsonic speeds. I start my load development high and work my way down in 0.5 grain increments. I then fine tune the load from there. Below 1000 fps is ideal for noise reduction.

I gave up on trying to get my SKS to cycle because of the lack of heavier bullets available at the time. I have no interest in renewing my project with bullets at this price.

I have a 12" barrel bolt action 300 Blackout and it is fun to shoot subsonic. I have loads for cast (210 and 245 grain) and 220 grain FMJs with H110. These bullets are considerably cheaper than the ones you are looking at.

The last issue is barrel twist. My 1:7 barrel will stabilize the heavier bullets while a friend's 1:8 will not. My 1:10 is strictly supersonic with my 125 grain load. I don't know if the barrel twist on an SKS will stabilize 255 gr.

My next project (too many projects, not enough money) will be a Derya 9mm with a 12 inch barrel. It will be pretty easy to load up subsonic for that rifle with readily available 147 grain bullets.
 
Brass balls said:
https://www.canadiangunnutz.com/forum/threads/subsonic-sks-a-few-initial-results.428908/
Click to expand...
Nice find but that thread only talks about Trailboss powder, which will never cycle a semi-auto.


homer76 said:
Quite a few years ago I played around with 180 bullets and Trailboss. I couldn't get the bolt to cycle and it essentially became a straight pull bolt action.
Click to expand...
Trailboss will never cycle a semi-auto. I've tried it. Basically it is impossible to get enough powder into the case.
 
CLW .45 said:
Nothing like downloading a supersonic cartridge with a mini bullet.

9 mm, 124 gr, at sub-sonic speeds, is probably a decent paper punch.

.30 calibre, 139 gr, at subsonic speeds, should also pierce that paper target.

But anything more important than paper, in the subsonic realm, should probably be fat and heavy.
Click to expand...
Not sure I'd qualify a .30 cal, 255gr bullet as "mini"

Long and heavy is just as good as fat and heavy and it has the capacity to fly further. Trying to shoot 45 ACP at 200 yds just makes it difficult.
 
Andy said:
I'm skeptical that: "approximately 13gr of CFE BLK will cycle an SKS."
Click to expand...
Me too. Hence this thread. Was hoping maybe somebody had tried it.


Andy said:
The only way to know is to try!
Click to expand...
Yea, I know. See above.


Andy said:
Besides CFE BLK, I'd also try a bit more of a but slower powder like 4198 and H322 - more gas volume at around the same pressure.
Click to expand...
I tried H322 in a SA 300 BLK and IIRC it did cycle the action but if memory serves, there seemed to be a lot of unburnt powder left over, which then just jams up the action.
 
I ran some tests with 180 grain Speer SPRN #2223 and CCI250 with a COAL of 2.150".
H4895 would cycle the action only above mach, so that flunked.
CFE BLK worked at 12.0 gn, but the group was poor and the cases were extremely sooty.
With IMR 4198, I was shaving mach's chin at 15.0 gn with reliable cycling, good group, and clean brass.
 
7.62x39 mm has a .311 diameter, the same as 7.62x54R AND .303 British. Try some 174 gr and heavier bullets. If you can find heavy cast bullets with gas checks, all the better. Be aware of possible detonation with certain powders and low charges. Good luck!
 
Bubba Yugga said:
I ran some tests with 180 grain Speer SPRN #2223 and CCI250 with a COAL of 2.150".
H4895 would cycle the action only above mach, so that flunked.
CFE BLK worked at 12.0 gn, but the group was poor and the cases were extremely sooty.
With IMR 4198, I was shaving mach's chin at 15.0 gn with reliable cycling, good group, and clean brass.
Click to expand...
If the 180gr flirts with subsonic operation then the 255gr should be able to accomplish subsonic operation. I even have 4198. Now I just need to find some brass and dies.


Monster Mike said:
Try some 174 gr and heavier bullets.
Click to expand...
You didn't actually read the OP did you? :rolleyes:
 
I Dont Care About You said:
If the 180gr flirts with subsonic operation then the 255gr should be able to accomplish subsonic operation.
Click to expand...
My guess would be to go as low as 12 grains of 4198, since the deeper seating will reduce available case volume for the powder (thus raising initial pressure), and the heavier bullet will maintain more pressure after passing the gas port. See where that chrono's, and you may be able to bump it up to get it to the 1050 fps sweet spot.
 
I load lots of CFE.BLK in other calibers. Not really relevant.
I did notice my subsonic loadin my 50 Alaskan wanted magnum primers to get to full ignition.. 458sc already uses magnum primers but cylceled well with CFE . And 500gr bullets
I think the powder very gassy by design.
I like cfe over all. Ladders well and dosent spike irratically.
 
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