Hornady SUBX 7.62x39 Barrel Twist Rate
- Thread starter AZgeek
- Start date
Nothing happened after 75 yards. Had a very limited amount of time to run out and test yesterday. Heading out to an actual range tomorrow where I can test out to 200.
Loading only 1 round in the mag at a time, I had 1 out of 5 hold back the bolt. So adding suppressor back pressure should do the trick. I'll take some pictures at 100 and 200 yards so you can see the group sizes. Need to do a bullet expansion test at say 100 yards soon as well.
I just ordered a 1-8 twist Faxon AR barrel to build out another upper just in case. I don't have an adjustable gas block on my current rig, so that's another reason to build another. I have an Surefire SPS 300 suppressor due to land this month. Pretty excited about shooting this round suppressed.
Loading only 1 round in the mag at a time, I had 1 out of 5 hold back the bolt. So adding suppressor back pressure should do the trick. I'll take some pictures at 100 and 200 yards so you can see the group sizes. Need to do a bullet expansion test at say 100 yards soon as well.
I just ordered a 1-8 twist Faxon AR barrel to build out another upper just in case. I don't have an adjustable gas block on my current rig, so that's another reason to build another. I have an Surefire SPS 300 suppressor due to land this month. Pretty excited about shooting this round suppressed.
I called Hornady tech support a couple of weeks ago and he said 1-9.5 or faster which was my guess too. I thought about trying them in my 1-10 barrel but even if it seemed to be stable I doubt I'd have the stones to try it with the suppressor for fear of even a one off baffle strike. Guess I need to go barrel shopping.
Hell yeah. I ordered some and will probably pull several and use in 300 Blk! Also, try out in my 7.62 x 39 upper suppressed. Thanks
Doesn't 300 BLK use a .308 diameter bullet? If so be careful as these are probably .310 or .311 diameter. You can always run them through a bullet sizing die to get them down to .308 if need be. Please let us know how they sound suppressed. Just confirmed it will be Thursday when I'm able to test stability to 200 yards.
So not sure if they are stable. Here are six shots at 105 yards. I was playing with holdovers so the results are not about accuracy. The three closest to the tape were using the same hold once I got close:
255 gr Sub-X 0.3105”
Gonna size some down to 0.3080” and some not for the .300 Blk trials. See how accuracy goes. Subsonic shouldn’t make much difference in pressures.
FWIW the loaded ammo is 12.7 gr of a ball powder.
Bullet is 0.1.5755 long.
Gonna size some down to 0.3080” and some not for the .300 Blk trials. See how accuracy goes. Subsonic shouldn’t make much difference in pressures.
FWIW the loaded ammo is 12.7 gr of a ball powder.
Bullet is 0.1.5755 long.
Last edited:
Actually, it may compress slightly but that possibly helps with consistency. Imagine the .308 WIN subsonic example. Too much empty space in the case and ignition can be inconsistent supposedly. I’ve only read about this but not tested it myself.
I did hold the bullet up to the case and that’s how I’m figuring none to slight compression possibly. Not very scientific
This would make great south texas javalina medicine. Those suckers usually come out pretty close and don't give a fuck. They'll creep up to you and just about almost step on your feet.
Follow Up on Hornady 255 gr Sub-X bullets in 300 Blk
First, the original pulled bullet (from Hornady 255 gr Sub-X 7.62 x 39) at 0.3105 stretched the Starline once fired brass
and would not chamber completely with the exception of one round with 9.0 gr A1680 and recorded 828 fps.
Second, once the bullets were resized to 0.3080, using a Lee .308 bullet sizing die, they chambered fine until filled with 10.9 gr and up of A1680. The bullets are 1.575 long!
Seekins SP8 1:7 Omega can
Magnetospeed V3
AutoTrickler V4 w/ Fx120i
Mitutoyo 500-196-30
67F 16% 30.03 in
A1680 255 gr Sub-X resized to 0.3080
GM205M
Starline brass x 1 firing
COL 1.3530
BTO 1.5780
COAL 2.128 approx (slight variances in length of 5-10 thousandths or so)
9.0 817, 910, 844 SD 47.8 (not sure what happened here)
9.5 891, 876, 895 SD 10.0
10.0 926, 907, 936 SD 14.7
10.3 943, 947, 935 SD 6.1
10.5 962
10.6 978, 1002
10.9 and 11.2 wouldn’t chamber due to compression of load
BCA 7.62 x 39 16” Govt profile upper Omega can
Hornady 255 gr Sub-X Factory rounds
12.7 gr of an unknown ball powder that isn’t A1680
1044, 1172, 1151, 1132 fps
First, the original pulled bullet (from Hornady 255 gr Sub-X 7.62 x 39) at 0.3105 stretched the Starline once fired brass
and would not chamber completely with the exception of one round with 9.0 gr A1680 and recorded 828 fps.
Second, once the bullets were resized to 0.3080, using a Lee .308 bullet sizing die, they chambered fine until filled with 10.9 gr and up of A1680. The bullets are 1.575 long!
Seekins SP8 1:7 Omega can
Magnetospeed V3
AutoTrickler V4 w/ Fx120i
Mitutoyo 500-196-30
67F 16% 30.03 in
A1680 255 gr Sub-X resized to 0.3080
GM205M
Starline brass x 1 firing
COL 1.3530
BTO 1.5780
COAL 2.128 approx (slight variances in length of 5-10 thousandths or so)
9.0 817, 910, 844 SD 47.8 (not sure what happened here)
9.5 891, 876, 895 SD 10.0
10.0 926, 907, 936 SD 14.7
10.3 943, 947, 935 SD 6.1
10.5 962
10.6 978, 1002
10.9 and 11.2 wouldn’t chamber due to compression of load
BCA 7.62 x 39 16” Govt profile upper Omega can
Hornady 255 gr Sub-X Factory rounds
12.7 gr of an unknown ball powder that isn’t A1680
1044, 1172, 1151, 1132 fps
New upper parts due to arrive tomorrow. Worst case I'm shooting on Sunday. My existing 1:9.5 setup has an older Surefire break that still may work. Calling them tomorrow to confirm. If not ,I'll only be testing the new 1:8 twist upper. I have a magneto speed so I can test velocity at some point.
Very cold and very windy today but did get out to the range. No baffle strikes on the the .308 AR10 or the two AR15's in 7.62x39. First time shooting suppressed so I was a bit nervous. My old Windham Weaponry with the 1:9.5 twist rate shot great albeit overgassed for the SUBX loads. Only shot two groups at 50 yards. One was .75 MOA and the other was .4 MOA. Pretty happy with that and super quiet!
Had problems with the new 1:8 twist Faxon barrel build. Could not get enough gas to cycle it suppressed. It shot fine with normal loads so not sure if I have a break-in or a gas issue. The good news is that a 1:9.5 twist barrel will stabilize the 7.62x39 SUBX load out to at least 106 yards per previous post.
Had problems with the new 1:8 twist Faxon barrel build. Could not get enough gas to cycle it suppressed. It shot fine with normal loads so not sure if I have a break-in or a gas issue. The good news is that a 1:9.5 twist barrel will stabilize the 7.62x39 SUBX load out to at least 106 yards per previous post.
Did a bit more homework on the 16" Faxon Gunner barrel I got for this new build. Found this on Midway:
A bit of a shock. I found the is thread on AR15.com regarding this scenario:
www.ar15.com
This implies that I can use 300 BLK bullets in 7.62x39 brass with just a reduction in neck size. I guess that's the good news but is there significant risk running .310/.311 rounds through this barrel?
A bit of a shock. I found the is thread on AR15.com regarding this scenario:
Can you shoot .311 bullets in a .308 barrel? - AR15.COM
Firearm Discussion and Resources from AR-15, AK-47, Handguns and more! Buy, Sell, and Trade your Firearms and Gear.
www.ar15.com
This implies that I can use 300 BLK bullets in 7.62x39 brass with just a reduction in neck size. I guess that's the good news but is there significant risk running .310/.311 rounds through this barrel?
Not a risk. I researched a lot and there’s a plethora of info dating way back on various forums. Especially when guys were buying dirt cheap bulk pulls from AK ammo and using them in 300 Blk.Did a bit more homework on the 16" Faxon Gunner barrel I got for this new build. Found this on Midway:
View attachment 8103501
A bit of a shock. I found the is thread on AR15.com regarding this scenario:
Can you shoot .311 bullets in a .308 barrel? - AR15.COM
Firearm Discussion and Resources from AR-15, AK-47, Handguns and more! Buy, Sell, and Trade your Firearms and Gear.
This implies that I can use 300 BLK bullets in 7.62x39 brass with just a reduction in neck size. I guess that's the good news but is there significant risk running .310/.311 rounds through this barrel?
And here I am telling you to be careful and what the hell am I doing?!
So we now know this bullets work without the need to resize down to .308. I'll check with Windham to see what bore size they use. Heading out tomorrow to shot both rifles out to at least 175 yards to determine if there are any differences in stabilization between the two twist rates.
So we now know this bullets work without the need to resize down to .308. I'll check with Windham to see what bore size they use. Heading out tomorrow to shot both rifles out to at least 175 yards to determine if there are any differences in stabilization between the two twist rates.
Got a chance to shoot these 255 SUBX's out to 200 yards today. The Windham upper with the 1:9.5 twist produced a 2" group early on in the session. Nice and calm, virtually no wind.
The new Faxon build with the 1:8 twist barrel produced 4.5" 6-shot group , but this was later in the session after the wind picked up considerably right at me. This probably contributed to the 2.5"drop increase and doubling of the group size. The two groups were also not shot back to back so again change in wind was a factor.
I also took a few shots through my CZ 527 bolt gun. Not good. Probably due to the .311 groove diameter.
Stability-wise, I cannot see that the 1-8 twist barrel produces better results than the 1:9.5:
The new Faxon build with the 1:8 twist barrel produced 4.5" 6-shot group , but this was later in the session after the wind picked up considerably right at me. This probably contributed to the 2.5"drop increase and doubling of the group size. The two groups were also not shot back to back so again change in wind was a factor.
I also took a few shots through my CZ 527 bolt gun. Not good. Probably due to the .311 groove diameter.
Stability-wise, I cannot see that the 1-8 twist barrel produces better results than the 1:9.5:
Update on my 7.62x39 subsonic journey. Its going great and has already exceeded my expectations! I've tested .308 220gr plated bullets and both the .310 245gr and 265gr Acme bullets. All three are stable and accurate out of my dedicated rifle. I've shot the 220's and 245's out to 438 yards. No problem hitting spots on rock faces and no signs of any instability. Shot the 265gr bullet out to 194 yards this past weekend and again accuracy was very good.
Here's a picture of the gang with a factory Hornady 255gr on the top. Did not have a loaded 220 on hand:
I took a shot a supported Kevlar vest just for the fun of it with the 220gr plated bullet from Everglades ammo. Impressive expansion. Final accuracy and chronio testing will be performed next time out, but here is my current 5 shot load data results:
220gr w/small rifle primers CCI #41 at 10.7gr of H110: Max 1087, Min 1006, Avg 1058, SD 35 COAL 2.200
245 Acme w/large rifle primers CCI 200 at 9.8gr of H110: Max 1091, Min 1040, Avg 1060, SD 19 COAL 2.207
265 Acme w/large rifle primers CCI 200 at 9.6gr of H110: Max 1100, Min 1053, Avg 1077, SD 16 COAL 2.248
I've observed that large rifle primers give me better SD's. Going to try some with large rile magnum primers to see if the SD tighten up some more.
Here's a picture of the gang with a factory Hornady 255gr on the top. Did not have a loaded 220 on hand:
I took a shot a supported Kevlar vest just for the fun of it with the 220gr plated bullet from Everglades ammo. Impressive expansion. Final accuracy and chronio testing will be performed next time out, but here is my current 5 shot load data results:
220gr w/small rifle primers CCI #41 at 10.7gr of H110: Max 1087, Min 1006, Avg 1058, SD 35 COAL 2.200
245 Acme w/large rifle primers CCI 200 at 9.8gr of H110: Max 1091, Min 1040, Avg 1060, SD 19 COAL 2.207
265 Acme w/large rifle primers CCI 200 at 9.6gr of H110: Max 1100, Min 1053, Avg 1077, SD 16 COAL 2.248
I've observed that large rifle primers give me better SD's. Going to try some with large rile magnum primers to see if the SD tighten up some more.
I'm trying to work up a good sub load for 7.62x39 as well. Good to see this up for others that are interested.
Welcome aboard Rebel. Seems like there is only a small number of members here working with this caliber. Maybe because both factory ammo and reloading components were very limited up until recently. I don't really know.
Anyway, forgot to add that crimping is really important. My Lee 7.62x39 collet crimp die does not work well when using .308 jacketed or .310 lead hardcast diameter bullets. Had use the taper crimp feature on my RCBS seat die to get adequate results.
Did a quick and dirty penetration test into water jugs using a modified tipped Acme 265gr and the factory Hornady 255 Sub-X. Two completely different results. Acme went right through 4 jugs and stopped after hitting a soft kevlar vest backstop. The Hornady was explosive and disintegrated. Could not find the Hornady lead core but I think it slipped out of the side of the 4th jug.
Not sure I want explosive traits in a subsonic round. Will test again in a more formal way and include pics next time out.
Not sure I want explosive traits in a subsonic round. Will test again in a more formal way and include pics next time out.
My man doing the Lord's work!
I want to get into reloading by 2025 and your experience is exactly what I'm looking for. I have multiple 7.62x39 rifles so that's what I would like to reload to squeeze the most performance out of the gun. I recently got the BRN 180 7.62x39 16" upper with 1/8 twist rate and I'm eyeing the XCR-L in the same caliber. I'm also interested in x39 subsonic loads.
What's your advice for someone who wants to embark upon the same journey as you?
Lets talk 7.62x39 first. Love the round for what it was meant for in a combat role. But if you handload, you can do some pretty cool stuff. My goto full-house load uses the Nosler 123gr Varmageddon. Super accurate out of all my 7.62 rifles. Got them going a safe 2545 fps out of my 16" AR15. You can of course push it faster in a bolt gun and a longer barrels
Most of all my subsonic load development is captured here. I've used 190 to 265gr bullets so wide variety of weights and types (hardcast, plated, cup and core) to choose from depending on your objectives. With Hornady making factory 255 SUBX and now offering the same bullet for reloaders, its a good time to jump on the 7.62x39 subsonic reloading train IMHO.
Most any member on this site can help with reloading questions. We all have our own way doing things but the principles are basically the same. Happy to help when your ready to get started.
Most of all my subsonic load development is captured here. I've used 190 to 265gr bullets so wide variety of weights and types (hardcast, plated, cup and core) to choose from depending on your objectives. With Hornady making factory 255 SUBX and now offering the same bullet for reloaders, its a good time to jump on the 7.62x39 subsonic reloading train IMHO.
Most any member on this site can help with reloading questions. We all have our own way doing things but the principles are basically the same. Happy to help when your ready to get started.
Spent some time this past weekend trying to find a crimping solution for shooting subsonic .308 bullets out of 7.62x39 cases. As previously indicated, my Faxon barrel has a .308 grove diameter so I can take advantage of this size projo. The big problem is getting any kind of crimp tension as the Lee collet crimp die expects a .311 diameter bullet. It does not work at all for .308 and barely for .310 projos. Dangerous IMHO especially for .308!
I was on the verge of trying to make some type of collet insert for the die to reduce the diameter but found another way. If you have or can source a 75 ohm coaxial crip tool, it works perfectly:
Its like it was custom made for this application. Just slide it in until it hits the shoulder, move back out a cunt hair and squeeze. The 4-point contact does not affect the roundness of the neck but i still run it through the collet crimp die as a precaution.
For loading up flat base Hi-Tec coated bullets I find it much easier to bell the top of the neck with a 9mm case bell die. Just barely is enough to ensure easy seating:
I'm sure there are better ways to address these issues, but zero cost here. Anyway, couple of Christmas loading hacks to consider for you cheap bastards out there.
I was on the verge of trying to make some type of collet insert for the die to reduce the diameter but found another way. If you have or can source a 75 ohm coaxial crip tool, it works perfectly:
Its like it was custom made for this application. Just slide it in until it hits the shoulder, move back out a cunt hair and squeeze. The 4-point contact does not affect the roundness of the neck but i still run it through the collet crimp die as a precaution.
For loading up flat base Hi-Tec coated bullets I find it much easier to bell the top of the neck with a 9mm case bell die. Just barely is enough to ensure easy seating:
I'm sure there are better ways to address these issues, but zero cost here. Anyway, couple of Christmas loading hacks to consider for you cheap bastards out there.
After reading this thread, I'm still not sure if it's ok to load .308 diameter bullets in a 7.62x39. Can anyone confirm that?
I'm researching making a 7.62x39 subsonic load for a friend, but the only .310 diameter bullets I'm seeing are 123s and I'd obviously prefer to load up 190+ grain bullets.
I'm researching making a 7.62x39 subsonic load for a friend, but the only .310 diameter bullets I'm seeing are 123s and I'd obviously prefer to load up 190+ grain bullets.
Maybe this is an AR/ US thing, IDK. I'm guessing these implementations involve a longer throat and a more gradual land transition. A 3 thou swage (assuming your shooting .311 ammo) is a bit scary.
BTW on Saturday I'm heading out to break my personal long distance 7.62x39 subsonic shot. Currently its 438 yards, Going for 500 meters with the Acme 245 grain load.
BTW on Saturday I'm heading out to break my personal long distance 7.62x39 subsonic shot. Currently its 438 yards, Going for 500 meters with the Acme 245 grain load.
@Dogtown
I’m have some factory loaded Hornady 255 Sub-X if you can’t find them and wanna try some. I actually pulled some and resized to .308 on a Lee resizer then put in .300 BLK.
Edit:
Looks like GunMag Warehouse has them for $30/box
Most all AK's are going to be a .310/.311 diameter bullet. Some of the 7.62x39 barrels for AR15's are setup for .308 diameter bullets, because the company already had .308 blanks for .300 BLK and .308 Win.
Hornady SUB-X Bullets 7.62x39mm (3115 Diameter) 255 Grain FTX Box of
The Hornady Sub-X (Subsonic - eXpanding) bullet features a lead core. Long grooves in its gilding metal jacket combine with the bullet’s flat...
www.midwayusa.com
Hornady SUB-X Bullets 30 Cal (308 Diameter) 190 Grain FTX Box of 100
The Hornady Sub-X (Subsonic - eXpanding) bullet features a lead core. Long grooves in its gilding metal jacket combine with the bullet’s flat...
www.midwayusa.com
Here’s my notes. I now remember having chambering issues before resizing to .308. They wouldn’t chamber and were very difficult to load in .300 BLK brass. Can’t recall all details unfortunately. Later the resized didn’t want to chamber once I reached 10.9 gn A1680 powder.
I think due to the length of the bullet and case fill maybe??
Out of a cheap 16” BCA 7.62x39 upper, here’s the limited factory ammo data w/ Magnetspeed V3.
3/16/23
67F 16% 30.03 in
Hornady 255 gr Sub-X
1044, 1172, 1151, 1132 fps
Pulled bullets, sized to .308 with Lee bullet sizer.
Seekins SP-8 .300 BLK
8” match 1:7” barrel, omega 30 can
3/16/23
67F 16% 30.03 in
*A1680 255 Sub-X 0.3015 from pulled 7.62 x 39 rounds resized to .308
GM205M
COL 1.3530 (old stock brass)
*BTO 1.5780-1.635? Varies due to .308 compression from 0.3105 bullet??
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
^^^so I need to play with 10.6 gn some more it looks like. That’s totally viable. Unfortunately did not record accuracy but I will and report back. I have a new Garmin Xero to use to give me some incentive
Edit:
Garmin is badass to say the least.
1/4/24
54F 39% 30.01in
255 Sub-X resized to 0.3080
A1680
GM205M
COL 1.3500 new starline brass
*BTO 1.625
COAL 2.18 approx
10.4gn 978, 969, 937, 963, 935, 952
937, 962, 973, 950 1.7” at 50y
10.6gn 999, 974, 948, 965, 958, 979 1.2” at 50y
Ejects but doesn’t cycle a new round even with AGB wide open.
Edit:
Garmin is badass to say the least.
1/4/24
54F 39% 30.01in
255 Sub-X resized to 0.3080
A1680
GM205M
COL 1.3500 new starline brass
*BTO 1.625
COAL 2.18 approx
10.4gn 978, 969, 937, 963, 935, 952
937, 962, 973, 950 1.7” at 50y
10.6gn 999, 974, 948, 965, 958, 979 1.2” at 50y
Ejects but doesn’t cycle a new round even with AGB wide open.
Last edited:
Jealous. I want a new Garmin chrono! The 255 subx resized for 300 blk might be more trouble than its worth based your results. I don't have 300 blk so can't help.
That said, I have plenty of AA1680 laying around but have not tried it. Next reloading batch maybe I'll compare it to the H110 loadings. Burn rate appears slightly slower than H110. I was going to try a slightly faster power to address my cycling issue (just not enough gas) that I initially encountered. Drilled the gas port slightly larger, replace the stock spring and buffer with the Yellow SpringCo setup. Close but still not quite there.
Turns out the real culprit my SA gas block setting. I had just a tad of front bleed off enabled. Just 1/2 turn back towards restrictive mode appears to have fixed it. For Saturdays shoot I upped the 245gr load by 0.1to 9.9 and cleaned the shit out of the gun. Should be GTG.
That said, I have plenty of AA1680 laying around but have not tried it. Next reloading batch maybe I'll compare it to the H110 loadings. Burn rate appears slightly slower than H110. I was going to try a slightly faster power to address my cycling issue (just not enough gas) that I initially encountered. Drilled the gas port slightly larger, replace the stock spring and buffer with the Yellow SpringCo setup. Close but still not quite there.
Turns out the real culprit my SA gas block setting. I had just a tad of front bleed off enabled. Just 1/2 turn back towards restrictive mode appears to have fixed it. For Saturdays shoot I upped the 245gr load by 0.1to 9.9 and cleaned the shit out of the gun. Should be GTG.
It’s a PITA process. Pulling, resizing, loading.
But, that’s some good energy at 50y compared to 190 Sub-X. Decent enough group.
Similar threads
- Poll
