Thread: Reloading subsonic 7.62x39

Anyone whom has made up some subsonic 7.62x39 homeloads. Could you please share your load data. That would be very appreciated and would save me some time. In developing a subsonic load. Cheers Brent

.7 gr of trailboss, one of @shooternz 151gr cast projectiles, win primer. That is my rifle, I would still start at 7.2/7.0 or so and work down until you hear it drop below super at about 6.9, then down .2 or so below that. Trailboss and sub loads are different in that you work your load DOWN rather up. Last thing you want is a projectile stuck in the barrel.

same for me...DONT use magnum primer or powder levels will get silly low trying to get it quiet..... justremember that terminal preformance is like an arrow...hit nerve centre or lungs and expect to wait a while before following up. zero shock power.

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.

Thanks Tommy, for all that info. A local gun smith said that the 7.62x39 case wouldn’t fit enough powder with trailboss. Even for a subsonic loss? You obviously didn’t have any troubles. You are right. I don’t want a pill stuck in the barrel. Especially if it tag teamed, with the previous bullet 😋 thanks again for your response 😋 Brent

This might help. Can't promise it'll get you subsonic though.

[QUOTE=PommyMcPomFace; the main use would be at the range at nothing over 150m. I have for a long while been interested in developing a sub load for this caliber. I think 7.62x39 lends it self to subsonic speeds, like the 300 blackout. Because of the smaller size case. And you are only giving up 1300 FPS on it’s normal performance. With the small amount of anti feeling with guns and shooting in NZ at the moment. Also shooting at rabbits etc in a semi rural area is probably best done with minimal noise. It would be good to have that option. I’m just worried about developing the load. With the obvious of the load not getting the pill out of the barrel 😋. I have a friend with a crony and I will definitely start with working down my loads. Scary stuff when you start from scratch. Cheers for responding to my post, Brent

Originally Posted by Max Headroom

Attachment 116779

This might help. Can't promise it'll get you subsonic though.

Thanks for that information. I have a screenshot of your post. It is s good start. They don’t talk about reducing the load from the 60% calculation. I guess you crony it and bring down the load to 1050 fps. Marking sure you mark each reduced bullet well. I have posted a question on Quora. About this matter. Surely some gun nut American has done this. I’ve seen I guy pull a wolf steel case round and reduce the powder to around 13.5-14 grams. Re seat the same projectile and he said it went subsonic? I’d rather work with a load that a reloader has developed. With appropriate powder like you have shared. Cheers for responding to my post. Brent

Originally Posted by brent17

Thanks for that information. I have a screenshot of your post. It is s good start. They don’t talk about reducing the load from the 60% calculation. I guess you crony it and bring down the load to 1050 fps. Marking sure you mark each reduced bullet well. I have posted a question on Quora. About this matter. Surely some gun nut American has done this. I’ve seen I guy pull a wolf steel case round and reduce the powder to around 13.5-14 grams. Re seat the same projectile and he said it went subsonic? I’d rather work with a load that a reloader has developed. With appropriate powder like you have shared. Cheers for responding to my post. Brent

I think that going below 60% of the original max load is unwise for this powder. At that load it's either subsonic or it's not.

Reducing powder loading too far can result in an ugly condition where the powder in the case doesn't burn in the correct way, and you have an explosion known as a flashover. You'll want to google that one.

plenty of room in the x39mm case for trailboss load to go ABOVE subsonic.....which is what I will do in future...for the little more noise you get the step up in impact is worth it... hint here,the LEE spoons make life really easy with the wee case,you will scoop into scale pan and not be far off at all.

I mean, if you want supersonic, there’s proper supersonic rounds for next to nothing cost wise, esp seeing all the semis have been gunnapped

Originally Posted by Max Headroom

I think that going below 60% of the original max load is unwise for this powder. At that load it's either subsonic or it's not.

Reducing powder loading too far can result in an ugly condition where the powder in the case doesn't burn in the correct way, and you have an explosion known as a flashover. You'll want to google that one.

I'm rather tired of hearing this myth, and the internet's allowed it to propagate far and wide. "Flashover", "detonation" or "secondary explosive effect" or whatever it's attributed to.
Manufacturers and laborotories HAVE TRIED and been UNABLE to replicate it with severely reduced loads.
So with all due respect, Got any facts?

I have a 220gn subsonic load with 2208 for .308.
In the olden-times it was recommended to hold your powder against the primer with dacron or cornmeal. I don't know of anyone who still does this.

As said, start high and work down. Shoot over a chrony and if you get a no-read or your bullet doesn't show up on target STOP and check the barrel, because an obstructed barrel will cause very bad day.
Do your load dev WITHOUT a supressor and check targets for tumbling or keyholing - if there is any, find another projectile.

The only reply I can think of to make is simply that if it were safe, the reduced load data for 4895 posted above wouldn't have the instruction to take the max charge and multiply by 60%,and work on up from there.

They'd simply say the formal equivalent of:
"Have at it, use what ever percentage loads you want, providing that this is a recommended powder for this round, and you're not going over the max load"

Originally Posted by Max Headroom

The only reply I can think of to make is simply that if it were safe, the reduced load data for 4895 posted above wouldn't have the instruction to take the max charge and multiply by 60%,and work on up from there.

They'd simply say the formal equivalent of:
"Have at it, use what ever percentage loads you want, providing that this is a recommended powder for this round, and you're not going over the max load"

I think it's a lawyer-proof thing, they don't want to tell their customers that they're idiots and probably pulled the trigger on an obstruction.
I wouldn't load down any super slow powders, anything slower than 4831 I would be particularly cautious of with low load densities.

Also in many cases you can go over the max load and be safe. I don't advocate this without the means to test actual chamber pressures (though plenty of people do it), but if you have a longer barrel than the one they used on the test data you're going to get higher velocities. A new bolt action is going to be stouter than a war era semi. Etc.
And if you know what you're about, there's no reason "published max" should be "actual max"
Recipes in loading manuals have been getting lesser and lesser over the decades, too. Not all of this can be attributed to hotter powders. Again, it's a lawyer-safe thing.

Originally Posted by mimms

I think it's a lawyer-proof thing, they don't want to tell their customers that they're idiots and probably pulled the trigger on an obstruction.
I wouldn't load down any super slow powders, anything slower than 4831 I would be particularly cautious of with low load densities.

Also in many cases you can go over the max load and be safe. I don't advocate this without the means to test actual chamber pressures (though plenty of people do it), but if you have a longer barrel than the one they used on the test data you're going to get higher velocities. A new bolt action is going to be stouter than a war era semi. Etc.
And if you know what you're about, there's no reason "published max" should be "actual max"
Recipes in loading manuals have been getting lesser and lesser over the decades, too. Not all of this can be attributed to hotter powders. Again, it's a lawyer-safe thing.

Thank you for all your posts. It’s quite daunting trying to get a subsonic load. I think I’ll try AR2206H at 60% with a crony. I’ll also make up some 50% loads. If the crony speed is quite high I’ll try the 50% loads. And definitely make sure I look down the barrel for a in cleared projectile. I was going to use a suppressor but on prev advice. I won’t. And I will look for any signs of bullet tumbling. I feel like buying a cheap norinco for this job. I would hate to ruin a ruger ranch rifle 🤔 Thanks to everyone that has posted here. I really appreciate your time to post. And help me with this project. Cheers Brent