Thread: 7.62x39 rifling groove diameter

My Ruger ranch rifle has a .311 diameter grooves according to the internet.
I have projectiles that are .310. It seams most projectiles for this caliber are this size. I have two neck resizers .308 and .311 (collets) in the Lee dies.

I have a couple of questions if someone would be kind enough to answer.

1. Should I try and find and use .311 projectiles (303)?
2. If using .311 collet with a .310 projectile will the projectile be held in the neck of the case well enough?
3. Should I try the .308 collet and try and get a pill in there. Hopefully, not damaging the brass case?
4. Any information you have regarding reloading this caliber would be appreciated. I was going to use CFE black. However, I have to travel to Auckland to get it. A local is selling ADI AR2207 powder. And it $20 cheaper. Any thoughts to save me time and hassle would be great.

5. Any ideas on bullet creep and the distance off the lands. For improving accuracy.

To anyone that answers my questions. Thank you in advance for sharing your knowledge.

Kind regards, Brent

Gidday Brent

My Howa 7.62x39 (since sold) shot just as well with .308 projectiles as .311 ones, both better than MOA. You'll find that as long as the projectile doesn't have a "sharp" radius on its base it'll seat just fine with either collet. Consistent neck tension is quite important to producing good reloads, but it doesn't really matter how much it is as long as it is consistent (and not so little that projectiles move).

CFE Black goers really well in this cartridge, I got 125 gn projectiles going at 2500 fps quite easily. I have some CFE Black left over that I'd sell (or you can have a wee bit to try if you like). PM me if you want to go down this path.

Cheers

Hi tentman, thanks for your reply.
I’ll try some .310 projectiles first and have a play with other sizes.
What part of the country are you in? I don’t think anyone with send powder😋

Uses the ssshhhhhh I won't tell if you don't tell shipping method.

I'm in Invercargill but will be in your neck of the woods in early Nov so could deliver . . . .

Originally Posted by Slug

Uses the ssshhhhhh I won't tell if you don't tell shipping method.

Yeah - or this . . . .

Originally Posted by mimms2

The only way to tell is to slug your bore.
But as above, either may shoot well, but you're more likely to run into pressure using big pills in tight bore. I'd be inclined to find out sooner than later.

Even then there are more factors at play like leade design etc. My .320 bore 8x57 happliy digests .323 projectiles (with superb accuracy) at full house loads. Much bullshit has been written by yank wannabe gunwriters that is completely wrong on this sort of subject . . .

.310" will completely seal a .311" bore when fired as the bullet displaces slightly when the lands push into it, causing it to fill the grooves. Displacement varies from .001" to .003" depending on the number of lands and their width.

What he said but with a picture

I put the 308 expander ball in my set of dies and left them there..... we loaded all sorts of .308 projectiles with good results....did try the 310 but not huge difference
to my way of thinking...7.62x39mm is a 150 yard game cartridge...it just runs out of steam too quick beyond that so accuracy of 2" at hundred is perfectly acceptable,no need for any better ,solid chest shots and deer fall over.
try some speer 130grn hps and nosler 125grn ballistic tips....

Originally Posted by Tentman

I'm in Invercargill but will be in your neck of the woods in early Nov so could deliver . . . .

Thanks Tentman, sounds great. How much powder do you have and how much would you like for it?
I can meet you in town, or where ever you will be. Can we send personal messages to swap details? Cheers for your help.

Thanks mimms2, I’m trying not to crimp. Maybe a misconception but I believe crimping reduces accuracy. I haven’t reloaded for twenty years. Im hoping to improve on my 1.5-2” groups at 100m with Barnaul steel case. PPU brass cased Ammo shot really badly. I’d love to get .5 moa at 100m but I maybe dreaming.
I’ll try the .311 and .308 collet and see which one holds the projectile better. I wanted to neck size but it only comes with a .308 collet. Maybe that will work?
Cheers, I appreciate everyone’s answers. And the fact other shooters are happy to share their time and knowledge freely.

I'm with Micky Duck on this re accuracy what you are getting is fit for purpose with that cartridge. I have no intention of reloading for my howa as I have a supply of steel case ammunition and 1 to 11/2 inches is fine. It's not a target rifle after all.
Barnaul is or has dried up but there is still a lot of Chinese ammunition around and hornady steel case with the sst.
Just my 2c

Thanks for all your information 👍

To help with not shaving metal buy a Lyman M die with both .30 and .31 expander buttons
it will make life a lot easier.