7.62x39 bullet/barrel diameter

[wolfee]

I've asked this question about a million times and gotten 10 million different answers. But, Ruger guys seem smarter than anyone else so I'll go with whatever concensus you come up with.

1. What is the bullet diameter of a 7.62x39 SUPPOSE to be?
2. Do all ammo companies load the same diameter?
3. Do all rifle companies make their guns with the same groove diameter?

I have had answers that suggest variation between 308 and 311. One guy even tried to tell me Ruger barrels were tapered internally(!) and started out 311 but squeezed the bullet down to 308 by the time it got to the muzzle.

 

[JFB]

How about SAAMI?

http://saami.org/specifications_and_information/publications/download/Z299-4_ANSI-SAAMI_CFR.pdf#page=65

 

[Mobuck]

1. What is the bullet diameter of a 7.62x39 SUPPOSE to be?
somewhere between .310 and .312 is common although some have been .308

2. Do all ammo companies load the same diameter?
NO

3. Do all rifle companies make their guns with the same groove diameter?
NO

 

[Galaxiedan]

Bullet .311 +/- .002

Bore .300

Groove .310

 

[Merle1948]

The comment about Ruger having tapered barrels isn't too far off. They did use an extra generous throating to allow nominal .311 bullets to swage down to .308 without dangerous high pressure.

 

[DGW1949]

The comment about Ruger having tapered barrels isn't too far off. They did use an extra generous throating to allow nominal .311 bullets to swage down to .308 without dangerous high pressure.

Plus, when any manufacturer (not just Ruger) sets out to build a 7.62X39 rifle, one of the decisions they have to make is whether to use a European chamber or a (US) SAMMI-spec chamber, which just like the ammo each prospective chamber is designed for, differ in some respects. Hence many of the "fail to fire" and/or "fail to eject" reports which we've all seen relative to the attempted use of foreign ammo in the Mini-30, which everyone likes to blame on hard primers, this or that coating or whatever...when in fact, it's sometimes just simple case of their chamber not being right for the ammo they picked.

No big mystery as to how to cure the problem at all. Just use the type of ammo which Ruger say's to use...it's right there in the manual.

DGW

 

[Jimbo357mag]

I believe I read that Ruger first came out with .311 barrels for their early Mini-30's and change to .308 later. ...or maybe it was the other way around. It might be noted that Ruger recommends only American made brass cartridges in their guns.

 

[mikld]

The 7.62x39 is a combat cartridge designed for combat weapons, and bizillions of rifles have been built and chambered for the round. Wartime production tolerances will be kinda sloppy and you'll find barrel dimensions from 310" to .314" (and I've read of new production guns using .308") and answers will be in the same range. You didn't say which gun you have so the best (only) way is to slug the bore.

 

[Biggfoot44]

Bore and bullet diameters do vary widely . Keep in mind that in the intended Mil usage, the accuraccy goal was 3-4 min of Running Dog Imperialist , with 100% reliability .

"Suposedly" when the Mini-30 was introduced, it used .308 bore, so as to be suitable for handloading with American bullets, as at the time .310-.312 hunting suitable bullets were not commonly on the shelf . However, the neck diameter was large enough to fire ctgs loaded with.313 bullets without pressure issues, making loose fit when loaded with bore sized bullets.

 

[gramps]

The mini 30 project was initially to be chambered in .308 Winchester. Ruger was unable to get the action to work reliably with the NATO cartridge, and then switched to the Russian cartridge. This is how it was explained to me in the 1990's, when I had a mini 30.
gramps

 

[Merle1948]

The mini 30 project was initially to be chambered in .308 Winchester. Ruger was unable to get the action to work reliably with the NATO cartridge, and then switched to the Russian cartridge. This is how it was explained to me in the 1990's, when I had a mini 30.
gramps

The original .308 effort was called the XGI, and was noticeably bigger than the Mini 30.