Hornady SUBX 7.62x39 Barrel Twist Rate
- Thread starter AZgeek
- Start date
New member but have been following this thread for a while.
I’ve had an x39 AR for about 13 years. It’s always been a track driver and even though barrel is .310 I’ve come up with some very accurate reloads using .308 bullets. Barrel has thousands of rounds through it but hasn’t lost any accuracy at all.
I finally pulled the trigger on a can (still in jail) but really want to work up a great subsonic load. My barrel is 1:10 twist so I’m nervous that I’d be risking blowing up the can if my barrel can’t stabilize the big slow bullets.
I would love to hear opinions from those with experience to help me.
I appreciate all the information that’s been shared here and will surely use it!
I’ve had an x39 AR for about 13 years. It’s always been a track driver and even though barrel is .310 I’ve come up with some very accurate reloads using .308 bullets. Barrel has thousands of rounds through it but hasn’t lost any accuracy at all.
I finally pulled the trigger on a can (still in jail) but really want to work up a great subsonic load. My barrel is 1:10 twist so I’m nervous that I’d be risking blowing up the can if my barrel can’t stabilize the big slow bullets.
I would love to hear opinions from those with experience to help me.
I appreciate all the information that’s been shared here and will surely use it!
My general rule of thumb with subsonic load dev: do a backwards charge weight pressure test to see if bullets are stabilizing around the 1000fps WITHOUT the can.
Some good advise here. Rigid cardboard is your friend to see the results of stability.
AR39 and “tack driver” don’t really strike me as realistic. Care to elaborate more on the build? Thanks.
Thanks I will definitely be testing without can first, I don’t even have it yet. Just not exactly sure how to tell they are stabilizing 100% other than inspecting paper holes.
It is a rifle that was built by AR Performance when they were still in Colorado. It was my first AR and I’ve made a few modifications over the years but it has always surprised me how accurate it is.
It’s kind of the only way to tell. Either you get clean holes at 75-100 yards, or you get oblong keyholes.
Interesting thread. Has anyone experimented with Hunters Supply slick coat? I have made a few these for 238 gr in both 311 and 308 dia, as well as 303 british in 174 gr. The HS 308 did not group well at all in my CZ 527. I am planning to make enough of the HS 311 to get good statistics and go from there. Have not tried Acme yet.
I just picked up 500 255 sub-x bullets and plan to load them in starline 7.62x39 brass with cfe black powder. Going to be shooting them out of a 12.5" ak with a sandman s. Anyone have an idea on where to start powder charge wise with these? I'm thinking probably 13-14 grn going off of 300 blackout data but I know case capacity changes things a bunch so just taking a wild stab at it. If no one has any insight I will shoot from the hip on this and try it and report back my findings.
So I loaded 5 rounds of each charge weight of 14, 13.5, 13, and 12.5 of cfe black in starline Virginia brass with the hornady 255 sub x bullets. Shooting them out of my 12.5" ak I got an avg of 1108 fps at 14 grn, 1068 fps at 13.5 grn, 1054 fps at 13 grn, and 1003 fps at 12.5 grn. I was shooting these through a sandman s so backpressure was not very high to help cycle the gun. The 13.5 and 14 grn load cycled fine every round, the 13 grn load cycled half the time and the 12.5 grn would eject but never loaded the next round. I shot these at 25 yards and groups were about what you would expect for an ak, but it looked like a few of the bullet holes were at a very slight angle. Gonna load up a few more at 13.5 grn and test them at 50 and 100 to see if they are stabilizing ok.
I just picked a box of 20 up of these Hornady 255 grain 7.62x39 SubX rounds.
Gonna try them in my 12" barrel 1:9.45 twist AK with a Dead Air Sandman K
Should these stabilize enough to avoid baffle strikes?
I am hoping to check reliable semi auto function, and to check groups and stability out to 50m and 100m
It will be awesome if they cycle my SBR suppressed AK reliably, and if they stabilize produce precise enough groups at 50-100m
Gonna try them in my 12" barrel 1:9.45 twist AK with a Dead Air Sandman K
Should these stabilize enough to avoid baffle strikes?
I am hoping to check reliable semi auto function, and to check groups and stability out to 50m and 100m
It will be awesome if they cycle my SBR suppressed AK reliably, and if they stabilize produce precise enough groups at 50-100m
Try them and see. I think you will be fine stability wise but I highly doubt it will cycle with a sandman k.
I can’t imagine getting a baffle strike from those. You could always message Hornady. Also would shoot a few unsuppressed and look for key holes on cardboard 5 and 10 yards out. Even keyholes doesn’t mean you’d have baffle strikes but if they don’t stabilize by 50 yards it may not be worth risking. I’ve shot them in 16” 1:10 suppressed with no issues.
Reporting back, the Hornady SubX 255 grain 7.62x39 did not cycle in my SBR AKM 12.5" barrel East German inspired kit build, that was with a relatively low back pressure suppressor on, Sandman K.
Rounds appeared marginally stable. Some evidence of keyholing at 50yds and 100yds, pictures related, but no baffle strikes.
Rounds appeared marginally stable. Some evidence of keyholing at 50yds and 100yds, pictures related, but no baffle strikes.
Attachments
16” 1:10 7.62 x 39
Magnetospeed V3
3/16/23
67F 16% 30.03 in
Hornady 255 gr Sub-X
1044, 1172, 1151, 1132
Wow surprised they are running that hot. I have shot 190 sub x 300 blackout factory ammo through a 16" bolt gun and they were averaging right around 1030. Most factory subs i have chronoed were way slow and inconsistent. I will have to try factory 255s in my 12.5 ak and see how they do.
I agree. I am going to shoot a larger sample with my Garmin at some point. I kinda fooled with them last spring then forgot about them. I have a lot of the projectiles so I probably just thought, who cares I’ll load my own. Initially I was pulling them from loaded rounds (because that was the only way to buy them), sizing them down to .308 and loading in 300 Blk.
I wish they made the 255 in a 308 size, not sure why they don't. I would love to be able to shoot them out of my 300.
I ran into chambering issues due to compression of powder at 10.9 gr A1680. I never actually mic’d them later to see why. I still have the rounds but haven’t followed up. I also didn’t open my AGB wide open to see if the bolt would lock back.
A1680 255 Sub-X (0.310) resized to 0.3080
GM205M
COL 1.3530 (old stock mixed brass)
BTO 1.5780
COAL 2.128 approx
9.0 817, 910, 844 SD 47.8 won’t lock bolt
9.5 891, 876, 895 SD 10.0 won’t lock bolt
10.0 926, 907, 936 SD 14.7 won’t lock bolt
10.3 943, 947, 935 SD 6.1
10.5 962
10.6 978, 1002 didn’t lock bolt
10.9 won’t chamber
11.2 (x2) won’t chamber
Have you ever considered using Hornady #3131 174 gr. FMJBT INVERTED?
Yes, inverted.
It has a .3105" diameter, just perfect, and if you want some expansion, the lead core is open at the rear with a good meplat at the end of the boat tail...
7,62X39 SUB
DÉCOUPE The ogive is intruding in the powder space which is a boon for reduced loads because the fill ratio will be about correct; I expect better SD because of this. Perhaps CFE-Blk will be OK, I figure 12 to 13 grains will be enough.
And also, there's a nice crimping groove at the right place!
I'm going to try these as soon as the temperatures go up a bit.
PP.
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