7.62 X 39 Groove Dimensions and Mil-Spec Ammo

[scottnc]

Regarding Rvssian mil-spec, what would be the smallest groove diameter you'd feel was safe to shoot it in? A pulled bullet measures .312". A pair of rifles measure .307" (slugged twice to be sure, yes that's tight for 7.62) and .3135" respectively. The .3135" shot mil-spec only fair, it is now on and really likes an NOE lead bullet sized .3155". The .307" is a new gun that has yet to be fired waiting for the last bits to cast and load lead bullets for it. In the mean time I'd like to shoot it some to check function using mil-spec, but with a delta of .005". . . I dunno if that'd be smart. The Russian bullets have an exposed lead core base. It looks like they are made to expand in the spirit of a minie ball, think they'd be forgiving of being squeezed down? Hate to mess up my new toy.

In looking for definitive barrel bore spec's there does not seem to be a consensus. .308", .310", .312" take your pick.

[Der Gebirgsjager]

There really isn't a set standard, other than what is correct for your individual rifle. The official bore diameter for 7.62x39mm is .311". Squeezing a .001" (.312") bullet through a true .311" tube isn't too much increase and may in fact compensate for a worn bore. If cast, most casters usually start by trying a bullet .002" over bore diameter. You can find bores from the factory in .311" and .308". Ruger made Mini-30s with .308" bores, and when I phoned and asked the sales people about the wisdom of firing .311" bullets through their .308" bores I was told "Our rifles are tough! They can take it". I have had factory loaded ammo with .308" bullets. On top of this consider the SKS rifles made by various countries, many now well used but some like new, bolt action sporters in 7.62x39mm from various countries and manufacturers, and all of the ammo loaded by various manufacturers in various countries and you'll find a spread in bore diameters and bullet diameters. So, in actual life experience, there is no standard adhered to by everyone, but the official bore and bullet size is .311". Most rifles will handle anything in the spread.

DG

[uscra112]

If the bullets had a gilding metal jacket, I'd do it, but I'd be leery of steel. Not because of pressure so much as what it might do to the rifling. But then, if it's a used rifle, what was being shot in it before you got it?

[deces]

People have shot millions of rounds of .311 Russian ammo out of Ruger mini 30s and now 300 crackedout ARs with .308 bore. This is much to about nothing.

[Larry Gibson]

The AK/SKS bulets, even the mild steel jacketed ones, are sized down to groove diameter (.307/.308) within the first bearing length of travel which is very early in the rise to pressure with jacketed loads. From that first bearing length of travel in the barrel they produce no more pressure than any other .308 caliber bullet of the same weight. I have done extensive pressure testing of them in 30-30, .308W and 30-6 rifles and have found any measurable increase of pressure, if any, was inside the expected normal test to test variation of pressure.

As always. just work up the load.

As mentioned; "This is much [ado] about nothing."

[uscra112]

Can't argue with real data.

[scottnc]

Thanks for the inputs. The rifle measuring .307" has never been fired. Being impatient sometimes has a cost, just want to avoid having a, "if I'd only waited moment".

[GhostHawk]

Don't sweat the small stuff.

My Yugo SKS which slugged and pound cast chamber came out .312 or .3115. It will shoot .3125 gas checked cast fine with no leading once I expended my sizing die from .311 to .3125. I mostly shoot the large for caliber 185 gr lee 2r gas checked boolit. I reduced powder considerably from factory loads. Ending up at 20 grains of IMR 4895. Once I got the bore truly clean and the lube right this gave me good accuracy with big punch.

The Mosin's I had to go to .314 sizing die to get things working. But the Crazy Yugo SKS likes them big and set long is not fussy about size.

[scottnc]

Ghosthawk - Getting off the subject; The rifle measuring .3135" is a smoked over SKS. Shooting a fat nosed 157gr fngc'd NOE bullet Al makes for the SKS and sized .3155" w/22.0 grains of 3031 it will shoot smaller groups at 100 than I'll lay claim to here. At 22.5 grains one round out of four hits about an inch high. Had to have Redding supply a larger neck button and modify the seating die to accept the large diameter nose.