Tuesday, December 26, 2023

And another round of experiments begins(and yes, there's a warning)

More subsonics.  This time 7.62x39 with a bullet actually designed for that bore.

If you've been following my rantings and diligent work to not injure myself, I tried using some .308" 200-grain Berry's bullets(intended for .300 Blackout) as subsonics in 7.62x39.  They worked, with an odd 'everything goes a bit to the right' problem I cannot figure out.  Well, Hornady has come out with a Sub-X load for that cartridge.  It uses a bloody long bullet of 255-grains.  It's been out a year or so, and the bullets are now available for handloading.  And I finally was able to buy some, which meant "What do I load them with?"

And now my standard DISCLAIMER:
There is no published handloading data for this bullet and cartridge, so I'm going by estimates and guesswork.  This- so far- has worked for me, which does not mean it'll work for you in your rifle.  If you give this a try, it's all on you.

And I'll be glad when they release some data on these.

Know a guy who got some other heavy-for-caliber bullets, 225 grains, and experimented with Titegroup, firing them in a AK47 clone.  He got them to fire with acceptable accuracy but they would not cycle the action.  And I didn't really want to use a pistol powder for these, so I did some comparisons with .300 Blackout loads with similar bullet weights, and put together five rounds with ten grains of CFEBLK, which I fired today.
The first two hit about 2.25" low at 15 yards*.  The other three were at 25 yards and about 4" low.  From the amount of drop I'm guessing the velocity was in the 800-950fps range, and the sound was much less loud than standard ammo.  The action(an AR-style rifle) cycled properly.  The primers looked normal, not flattened or otherwise indicating high pressure(I know, that's not a reliable indicator, but it's what I've got).  The first try with the Berry's .308 bullets and 12 grains the bullet drop at 25 yards was about 19", so this is a great improvement.  Also means I really have to be careful watching for pressure signs.  I'm wondering if part of the difference is these heavier bullets are causing enough greater recoil to push the barrel up a bit more?**   I'll need to try these over a chronograph, and when opportunity arises through a suppressor.

So it's a start.


*15 because the first try with the Berry's had been low enough that, if I'd been using this size target, it would've missed the paper at 25, so in case these were that low...

**If you're not familiar with this, it's really pronounced with handguns.  Take one whose sights put a load dead-on at 25 yards.  Shoot it with a lighter-bullet higher-velocity load and it will very often hit low on the target because the lighter bullet leaves the barrel before recoil can push it as high up as that of the heavier bullet does.

7 comments:

Anonymous said...

4350. Cant go wrong with 4350

Anonymous said...

4350 may be a bit too slow for that small case. A friend of mine does shoot 4350 out of a 22br with an 80 gr bullet though so I could definitely be wrong. I'm looking at the new Ruger ranch in 7.62x39 so I'll get to find out for myself, and hopefully soon.

Anonymous said...

Too bad Trail Boss is non-existent this year. Gave the last bottle I had to my brother. Subsonics with it are easy.

Firehand said...

LOT of people ask about Trail Boss at work, but none as yet. Anywhere.

Lowell said...

Can you get IMR-4064?

Firehand said...

I still have a little. It's looking at everything and trying to figure what and how much.
C'mon, Hornady, put that data out!

Anonymous said...

Maybe more twist is needed to stabilize the heavier bullets at low velocity, like how the 8.6blk uses a 3:1 rate of twist. Maybe this reasoning could apply to your application also...