Shooting .308" bullets in a 7.62x39 barrel. (AR47)

[Ledd Slinger]

Recently put together an AR47 with a side charging upper receiver and was wondering if any of you have input or experience with shooting standard 30 cal (.308" diameter) bullets in a 7.62x39 barrel (.310"-.312" diameter)? Looking to go with 120-150gr bullets. I will slug the barrel sometime this weekend to see where I'm at on actual bore diameter because I know things can vary, but just wondering what your personal results have been for accuracy and the load recipe you used. Thanks.

 

[joshb]

Nice gun. I tried it in my Wyndham. They shot but I had trouble getting enough pressure to get them to shoot fast. I have a ton of Sierra 125s, so I really wanted it to work. It didn’t.
If I was desperate (no other choice) , I could defend myself with them.

 

[Ledd Slinger]

Nice gun. I tried it in my Wyndham. They shot but I had trouble getting enough pressure to get them to shoot fast. I have a ton of Sierra 125s, so I really wanted it to work. It didn’t.
If I was desperate (no other choice) , I could defend myself with them.

How fast are you talking? Usually a slightly larger bore will yield faster speeds, but im sure theres a point where the gap becomes too wide and diminishes the returns. I picked up a box of 100 Speer 125gr TNT bullets to try and was hoping for somewhere in the 2300-2400 fps range. Did you also happen to know the actual bore diameter of your Wyndham barrel?

I slugged my barrel from the factory after only running a couple cleaning patches thru and it came out at .3055". I know that can't be right so I scrubbed it hard with a bronze brush and got enough crud out to where a .308 cal brush didnt feel very tight. Want to scrub it harder tho, so i just picked up an extra cheapo .338 brush to run so i dont ruin my good brushes. Once i get it cleaned out really good, I'm sure the next slug will show a larger bore diameter. Will post my results when I slug it again after a thorough cleaning

 

[Ledd Slinger]

Well I cleaned the heck out of the barrel and re-slugged it. Still came out at .3055" so looks like this barrel has a tight spot, but it fwlt tight for the first 6" in front of the chamber instead of the end of the bore like most barrels. Don't feel a tight spot with a tight cleaning patch anywhere tho. I have ran 3 slugs thru the barrel now and all had the same exact measurement of .3055"

Due to my slug results, thinking I better start with .308" bullets.

 

[joshb]

“How fast are you talking?“ I don’t know. I don’t usually chrono my loads until I’ve found a good one.
I rough sighted the gun at 25 yards then moved to 100 to test the loads I made up using H4198 and the 125s. I had a tough time getting the shots on paper. I figured I’d have to adjust my scope a little, to be on at 100. Figured out my first few shots were hitting the dirt in front of the target. Using all the adjustment in my Monarch 8-32, my shots were still 10 inches below the bull.

 

[Ledd Slinger]

“How fast are you talking?“ I don’t know. I don’t usually chrono my loads until I’ve found a good one.
I rough sighted the gun at 25 yards then moved to 100 to test the loads I made up using H4198 and the 125s. I had a tough time getting the shots on paper. I figured I’d have to adjust my scope a little, to be on at 100. Figured out my first few shots were hitting the dirt in front of the target. Using all the adjustment in my Monarch 8-32, my shots were still 10 inches below the bull.

So how do you know you had trouble getting the .308" bullets to shoot fast? Hitting the dirt and running out of adjustment sounds like a scope rail to barrel alignment issue, not a slow moving bullet

 

[joshb]

So how do you know you had trouble getting the .308" bullets to shoot fast? Hitting the dirt and running out of adjustment sounds like a scope rail to barrel alignment issue, not a slow moving bullet

Sorry…..I’m not long winded. I presented the basic problem I had.
Of course I thought I had a scope problem and switched to another scope, blah blah, but the second time I went out, I took some factory ammo along that had the .310 bullets.
What else would explain a 20-25 MOA elevation difference between factory loads and the handloads?
Do your own test with YOUR gun. I’m not telling you it won’t work. I’m telling you how it didn’t work in MY gun.

 

[durand mortenson]

Have you checked the accuracy of your measuring tool? Just a thought.

Mort

 

[Ledd Slinger]

Have you checked the accuracy of your measuring tool? Just a thought.

Mort

Yeah I have gauge pins and other known objects I check regularly. I have a digital micrometer as well that measures down to half a tenth, but i dont think i need to get that specific with this particular rifle. Here's one of the bullets I'll be testing, comes out right at .308" on the vernier.

I'll scope the barrel today to check for flaws or anomalies.

 

[Ledd Slinger]

The main reason I'm wondering about .308 bullets in a 7.62x39 barrel is because there are far more bullets options in 30 cal and I can buy some of the 308 bullets for half the price of .311 bullets if i want to do some high volume shooting. I've read many success stories online about 308 in 7.62x39, but just looking for extra input from folks on here

 

[bpd459]

Greetings,
I’m overthinking your issue…. I would try the cheapest, light hollow point bullet you can find and try the fastest powder within range. One would think, me anyway, this would give the most opportunity for the bullet base to obturate.
Best of luck,
John

 

[lloydx2]

Saami is .311. I have a radical arms that slugged at .311. I took off the flash hider
and poured Cerrosafe down the barrel. Its makes sense, why would you sell a 7.62x39
with a 308 bore knowing someone is going run Chinese 7.62x39 (.312) ammo. I know guys like Craddock precision with make a .308 barrel. My Radical shot 1.125 @ 100 with130MK (.308)
Its a 500 gun. You might try some quality .312 bullets at 45 dollars a box. Let me know.
I have 3, 1100 round crates of Chinese ammo that I bought for 125 a case back it 85
It shoots 7 inches at 300. I love it

 

[D-4297]

Have a Chi-Com SKS that I tried .308's in some years back . The only thing that it told me was the more rounds I fired , the more the group opened up on the target , so I bit the bullet and bought .311's for it . Target was at 100 yards , and first five shots were 10's . After that it was 9's & 8's . Rounds stayed within the 12' x 24" "Center Mass parameter if that's worth anything to you .

 

[Ledd Slinger]

Have a Chi-Com SKS that I tried .308's in some years back . The only thing that it told me was the more rounds I fired , the more the group opened up on the target , so I bit the bullet and bought .311's for it . Target was at 100 yards , and first five shots were 10's . After that it was 9's & 8's . Rounds stayed within the 12' x 24" "Center Mass parameter if that's worth anything to you .

Thanks. That's great info. I will watch for fliers and keep track of round count as the barrel warms up.

 

[Zero333]

It's normal for a parts kit to include a 308" barrel instead of one that's .3015" - .3012"

I always slug the bore and use an actual micrometer... I have 2 SKS's... One I use ALL the time and the other is a collector all #'s matching so it's in the safe all the time.

The one I use Mic's @ 0.3016
So .3010" and .3012" bullets are just as accurate.

I use the Hornady .310" 123 gr SP.

Not only is it a range gun... I've hunted deer with it as well... it's an amazing do it all rifle.
It carries nicely and withing 100 yards no deer is getting away no matter how fast they run.