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Discussion Starter · #1 ·
Greetings,

I have a 90’s era AK47 in 7.62x39, receiver is US made, and I am not clear on the country of origin for any of the rest of the original parts. I made a couple Form 1 Suppressors last year in 7.62 caliber, equipped with a rear adapter for a YHM QD mount. I ran both on some .223 rifles, a couple 308 ARs and got around to the AK most recently. The threads were far more ‘true’ than on my US made M1A Socom 16 :roflmao: Anyway, subsonic data has been hard to come by for the 7.62x39. It’s there, if you spend ages searching for it, but really tough to verify.
There is this guy: which is a fair reference point.

First, my objective: I want a reasonably accurate subsonic load I can shoot out of my AK without any mods other than the suppressor. I would like it to at least cycle unsuppressed.

Why not use 300 blackout? Because AR15. that’s why.

so, I managed to stumble across some numbers with many powders, but I am a bit nervous about pistol powders. I ended up with some range pickup x39 brass and the die was cast, so to speak. With my shooting buddy assembling a 300 blackout upper for his AR, I had to act.

I found data for AA1680 and AA5744, the latter looking the most promising. The data I found on the internet, which assures its veracity... :roflmao: showed 5744 using between 11-12 grains of powder with a 180 grain projectile. I was able to source all the components at a local show. 174 grain Hornady FMJ .303 bullets. I tried 3 charge weights, using a COAL of just under 2.2”

12.0 grains
11.7 grains
11.5 grains

For my rifle, 11.5 seemed too low. I had 2 malfunctions; one was unsuppressed, didn’t eject the brass. 11.7 and 12.0 cycled the action, feeding another round. I’ve seen reports on the ’net that others have gotten lower charges to work. Good for them.
Accuracy was acceptable at 25 yards but I didn’t have enough rounds to play with to get a read on group size; I was focused quite a bit on checking for key holing, making sure I had new holes in the target for this trip.


all 3 charges showed db readings of ~118 db from my meter at my local indoor range.
I have some 200 grain projectiles enroute. My next trip should be with 11.8 grains of 5744, using the same 174 grain FMJBT.
 

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Well what your loads are showing is that you will get that smurf.
Good information and thanks for the input and Welcome to the forum.
Why such a heavy bullet?
 

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Discussion Starter · #4 ·
The heavier bullet should be easier to keep subsonic and cycle the action. Well... generally, as compared to the ubiquitous 123-125 grain pills. Also, the heavier slugs will retain more usable energy over a longer distance. I know that’s relative considering we’re talking about velocities under 1050 fps give or take.
 

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Well if you (I'm just asking not picking at you) are basically getting pistol velocities
and are using a heavier bullet, why won't pistol powders not work? The .45 comes to mind.
950 fps, 230 grain and a really short case compared to the x39. Is it because the powder
burns too fast? Now I do not know the difference(in volume) of the .45 case and the x39
case but I don't think the pressures would be that much different.

Please understand I do not know( I have never reloaded ) I am just trying to understand.
 

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Ive done alot of testing with subsonic 7.62x39. Pistol powders will work for subsonic loads but will not cycle the action at all or reliably. Pistol powders burn too fast and the pressure is not there to cycle reliably. Ive had luck out of my SBR 9 inch barrel getting 123gr amax pills to stay subsonic and cycle reliably. I use IMR 4227 in my subsonic loads 123gr-174gr. Seems to work just fine. Ive had the best accuracy out of a full sized akm using 154gr pulled steel core boat tail x54r projectiles
 

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Another issue with the lower powder charge weights is inconsistent burns due to the way the powder is dispersed within the case. Alot of internal volume and not much powder means the powder does not stay against the primer.
 

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Discussion Starter · #8 ·
Thanks ! I’ve got 4227 listed on the list of potential powders. I’ve seen some warnings about low powder to case capacity ratio being dangerous, so seeing charge weights in the single digits has made me less than comfortable while considering a charge to start from. I’ve seen intermittent reports of getting the AK action to cycle with some typical pistol powders, but the ones I saw that seemed to have the best followings were 1680 and 5744. I certainly have enough projects going on that I was hoping for success with these 2 powders. So far, 5744 is showing great promise.
 

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I haven't had any issues with IMR 4227. My crono tests with it usually keeps the fps +-20. It burns well with any charge weight. I haven't run into any inconsistencies with the burn.
With my tests opening the flash hole doesn't do much in terms of making the rounds more consistent. I have also pulled projectiles from tula, and wolf steel cased ammo dumped the powder and loaded subsonic rounds only changing the charge to my desired weight of 4227. They work and are as consistent as modified brass cases with larger flash holes or using magnum primers. I mainly use just regular large rifle primers CCI or winchester. Magnum primers you have do down load your charge even more.
 

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Discussion Starter · #10 ·
Thanks, that’s helpful info on 4227, Tula and Wolf. All of my local indoor ranges are ‘magnetic projectile’ unfriendly, so I may swap out my remaining wolf projectiles too. I haven’t drilled any of the flash holes but I am marking the brass to keep straight what I’ve got on hand.
 

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Discussion Starter · #11 ·
My load development took a slide backwards. I had about a magazine full of 174 grain over 11.8 grains of 5744. I had 2 malfunctions unsuppressed, and 1 or 2 suppressed. However... I jumped the gun a bit. My first 2 batches of subsonic were done without the benefit of a case gauge to check head space. It came minutes before my range trip and the rounds I took as a sample didn’t pass. I will alter my resizing die accordingly and either retest with the same or slightly more powder. I need more brass to mess around with here too. Sound is good, I’m seeing 118 - 119 right at the muzzle (of the suppressor ). Back to the reloading press !
 

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What helped me out alot is i bought a neck sizer. I only full case length resize after about three firings. Your fps will become more consistent with fire formed brass. I use a free decibel app which i dont know how accurate it is but im reading about 100 db at the muzzle end. The action cycling is louder than the projectile leaving and the expanding gasses. My rem. 700 308 reads about 90 db at the muzzle. You will probably always encounter feeding and cycling issues unsuppressed.
 

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Subsonic is a bit tricky indeed, I never finished my development of a round that could cycle an AK but I will be readdressing that hopefully this year.

Also I probably would not trust any "ap" on a phone for sound measurement (other than for a non accurate "reference" point) as they are usually nowhere near fast enough to catch the rise time required to catch the full intensity of the sound of firing. I have seen a bit of sound testing done on weapons over the years and the equipment to measure it properly is generally costs into thousands of dollars.
 

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Discussion Starter · #15 ·
Subsonic is a bit tricky indeed, I never finished my development of a round that could cycle an AK but I will be readdressing that hopefully this year.

Also I probably would not trust any "ap" on a phone for sound measurement (other than for a non accurate "reference" point) as they are usually nowhere near fast enough to catch the rise time required to catch the full intensity of the sound of firing. I have seen a bit of sound testing done on weapons over the years and the equipment to measure it properly is generally costs into thousands of dollars.

Yup! The phone mic’s are equipped with a cut out, so you’re not getting accurate reading over about 100db. It’s good for ambient noise, etc. FWIW, I got a db meter off amazon for ~$30 or so.

I was kind of expecting I would have some trouble but I wasn’t expecting the samples to be as far out of headspace as they were. once i saw that, I knew I’d be doing another round of testing... Darn! :)
It’s just odd having a malfunction in an AK. I got my 200 grain projectiles also, so I may have more than one load to test next time.

I expect I may not land “the perfect load” that will stay subsonic and cycle the action unsuppressed but I’ll have a go nonetheless. I just want to avoid having to build up an AR platform 300 blackout for this. Eventually, but I would rather have my AK to do it.

I forgot to mention I did have 2 oddities.
1) LOTS of un burnt powder. I think I understand this, but maybe drilling the flash hole wouldn’t be a bad idea... I also need to get a chrono in on the equation too.
2) at each of the last 2 sessions I’ve notice one questionable hole in the target. it looked like a keyhole, but more like an unstable in flight hit. before firing suppressed, I ran a few rounds through at 5 yards with a good backing and was getting clean round hits. The suppressor has not been hit. I checked it thoroughly so -if- it’s the bullet not stabilizing it’s going unstable down range. It’s been one hit on target each time, and both times, it’s just been a ‘not quite clean’ hole. I’ve shot a barrel out of a 1919, so I know what key holing looks like. Unfortunately, because I wasn’t really paying attention to the hits per load for accuracy, I don’t recall which one it was the first time out, but the last time it was 11.8 grains of 5744 pushing the 174 grain Hornady FMJ.

With the snow, hopefully I’ll get done with the plowing soon enough to get some work on the next loads done
 

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Yepper, it is quite a challenge to get it all just right, as for your possible keyhole issue it could be due to the projectile possibly just being barely stabilized when leaving the barrel and losing stability further downrange where it starts degrading to the point of wobble or slight yaw to keyholing. I've seen that happen before with other subsonic ammo...It is so much easier to get the proper balance in supersonic ammo.
 

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"A chrono really is necessary for subsonic load dev though."

That is why I stopped did not have a chronograph to tell me how close I was. I am hopefully rectifying that this year.....
 

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With 300BO and 7.62 Mini-Whisper load dev it was crucial as I was working down and could stop once I hit my desired speed vice just trying to listen for the lack of a sonic crack downrange.

Would have been been doubly hard to listen for it as I didn't put the suppressor on until I had them at the desired speed and put a few on paper at 5y and 25y to check for round holes.

OP: you might be seeing key holing or destabilizing rounds on the paper, but without a chrono you don't know if you're at 1050fps or 850fps. Might also be that the load has a really wide ES, leading you to have 4/5rds fast enough to remain stable and an outlier that drops in speed a significant amount and gives you the out of round impact hole.

Might also want want to see what twist rate you have in your barrel for grins and compare that to twist rates in .308 and the bullets that match well to them.
 

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Discussion Starter · #20 ·
Agree 100% on the chromo. I don’t have one myself, but my shooting buddy does. it’s definitely needed info and will help validate or invalidate some of my efforts so far. i got a bit ahead of myself in development by overlooking the case gauge. I’ll try to tighten this up a bit.
 
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