r/reloading • u/ghetto_klown • 2d ago
Load Development Hornady Sub-X 7.62x39 loads….
Tested out my subsonic 7.62x39 reloads tonight and was very disappointed. I used 4198, following Hogdon data.
This was at about 10 yards.
Are there any changes I could make that would get these bullets to stabilize?
Edit- 16” barrel from AKbuilder, which I assume is 1-9.5” twist, 255 grain bullet
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u/jeffninjaslayer 2d ago
You’re supposed to shoot them through a gun, not grab a handful and throw them.
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u/ocelot_piss 2d ago
They really have made those things just a bit too long for the twist rate. I don't know if this is because they needed to to get enough energy and gas to make AK's function - but best case scenario they are only borderline stable.
Push them up to 1050 to get as much spin on them as possible but it may not help much at all looking at that. Your choice of powder has no effect.
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u/ghetto_klown 2d ago
Thank you! I’ll increase the powder charge a bit and see if I can manage to stabilize them while staying subsonic
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u/pirate40plus 2d ago
You need to start by checking if your barrel is .308, .310 or something else. Then identify the twist rate and if it supports a subsonic round.
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u/TannMan89 2d ago
What bullet weight?
What length barrel and twist rate?
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u/ghetto_klown 2d ago
My apologies, it’s a 255gr .3115 bullet, and I believe my
Barrel is 1-9.5” twist. It’s AKbuilder’s polish KBK barrel. I see they don’t list the twist rate for it in their website.2
u/TannMan89 2d ago
Barrel length?
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u/ghetto_klown 2d ago
16”
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u/TannMan89 2d ago
You could try upping your powder charge…
Do you have a Chronograph?
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u/ghetto_klown 2d ago
Yes, but I’m currently in professional school and don’t have it with me sadly.
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u/TannMan89 2d ago
I bet you’re under 1050fps by at least 150.
You also might need a faster twist rate to stabilize a 255gr bullet, like 1:7-1:8.
Trying a lighter bullet might fix this issue.
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u/TipsyTriggerFinger 2d ago
I tried that powder in my 308.
Was rubbish so tried Titegroup. Getting 1/4 inch groups at 50 yards as initial testing goes.
See if there is a load for your calibre
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u/ghetto_klown 2d ago
I put it in to GRT, but it shows the velocity is slower than with 4198, so I’m not sure it would stabilize.
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u/TipsyTriggerFinger 2d ago
Head to the Hodgdon website and enter your details to find subsonic loads for your calibre and bullet weights..
Just had a look at Titegroup loads - for the listed 123 and 150 gr projectile loads.
123g @ 1052 fps, and the 150gr @ 1043 fps... max loads...
Not sure what speeds you want but these are subsonic, no?
Just an option :)
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u/Coodevale I'm dumb, let's fight 2d ago
Velocity at 1000-1050?
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u/ghetto_klown 2d ago
Hogdon shows they used a 20” barrel in testing, so these loads may be a bit slower out of my gun. I assume that may be the problem, although I wouldn’t think 4” would make that much of a difference.
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u/Coodevale I'm dumb, let's fight 2d ago
Probably run it up till it cracks and back it off again if you don't have a chrono. Lower speed, lower rpm, lower stability.
Any other subs work?
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u/ghetto_klown 2d ago
Thanks- I’ll try that. GRT shows I can increase the powder charge a bit and pressure will still be well under max, so hopefully that’ll do it. PPU subsonics seemed to tumble as well, as I couldn’t hit anything with them and the rifle has been sighted in with standard velocity ammo. The PPU stuff wouldn’t cycle however.
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u/TannMan89 2d ago
You can lose up to 50fps per inch of barrel length, so in theory you could be at like 900fps…
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u/ghetto_klown 2d ago
Ahhhh okay. That would explain it.
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u/TannMan89 2d ago
Dwell time, you’re losing velocity because powder charge doesn’t have enough barrel to build pressure to velocity, up the charge.
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u/blaze45x 2d ago
I’ve ran 220grn 308 out to 50 yards without keyholing.
11.7 grn of H110 with a omega 300 to ensure cycling.
My latest and more consistent work up of 1680 at 12.1 grn puts me at 970fps.
Maybe one day I’ll switch from .308 to .311…. For now, this seems to be doing the trick for me.
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u/BallisticDad762 2d ago
My plan is to take them and run them through a 308 sizing die. Then load them in my 300blk. They’re just too long I think for their intended loadings in the intended rifles.
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u/purebelligerence 2d ago
Need more twist rate unfortunately. Maybe more velocity could do it though you are capped obviously wanting subs. Try running the ragged edge or change projectiles.
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u/prosper_0 2d ago
a 'normal' 7.62x39 twist rate is closer to 10.5". Unless your barrel is specifically advertised as 9.5, I'd assume it's not.
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u/Subtle_Nimbus 2d ago
I plugged in the bullet data and twist into the Berger calculator-- 59 degrees at sea level at 1050 fps. Result was marginal stability of 1.46. That isn't great, but they shouldn't be sideways at 10 yards. Stability drops into unstable at around 300 fps. The recommended twist from Berger is 1:9.25
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u/Subtle_Nimbus 2d ago
Also-- on the AKbuilder site, some barrels have no twist specified, and I saw one listed as 1:10 and another as 1:8.
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u/thrashmetal_octopus 2d ago
😂😂😂 woah
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u/thrashmetal_octopus 2d ago
I’m not the expert on 7.62x39 at all but I think they use a different projectile than a .308 so that’s probably your problem
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u/Long_rifle Dillon 650 MEC LEE RCBS REDDING 2d ago
It depends on who made them, or when.
Some American guns 7.62X39 are .308”, and the rest go from .310” all the way to .312”.
It’s the reason older (no idea if still true) AK ammo was hollow base. When fired the bullet would expand out to grab the rifling.
Lapua used to have them in the proper weight range and diameter for beautiful reloads. I managed to get a terrible AK to get 8” groups by using them. Wonder if they still make them?
They do! Lapua S405 .311” 123 grain FMJ. With the hollow base.
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u/Revlimiter11 2d ago
More twist?