Re: 7.62 x 53R or 54R capabilites

02 September 2004, 13:55

Paul Brasky

Denton, I was firing Hansen ammo. with a 180 or 185gr. SP that evidently was too hot (or the bullets were too wide, .311" rather than .310") for my M 28/30. Most of the primers were pierced, but the last one I fired "disassembled" the bolt and ejector (easily reassembled). Neither I nor the gun was harmed by the escaping gas, if indeed there was any. My point is that the rifle handled it very well, as I didn't even know the gas had escaped until I opened the action and the bolt fell apart. ...Maven

02 September 2004, 14:06

denton

Well, that's certainly comforting. Maybe there isn't quite as much reason to be conservative.

Some commercial ammo is a bit on the hot side. I've measured some S&B 180 at 58 KPSI, which is hotter than I generally like. OTH, I have run my Finn up to 65 KPSI as part of an experiment, with nary a whisper of a problem.

Ackley did a test, and found that it takes very little force to swage a bullet down a bit... even an 8mm bullet in a .30 cal bore makes little difference in peak pressure.

02 September 2004, 16:06

Ricochet

Quote:

Ackley did a test, and found that it takes very little force to swage a bullet down a bit... even an 8mm bullet in a .30 cal bore makes little difference in peak pressure.

Ackley was using lead cored, copper jacketed bullets. Many bullets for the 7.62x54R have mild steel cores, a thin layer of lead over that, and a copper washed mild steel jacket. I'd be more leery of shooting these through bores much undersized.

Personally I wouldn't be worried about commercial .308 level pressures in any Mosin in good condition, and I've suspected from the ballistics that much of the Eastern bloc ammo is so loaded. But I don't have any pressure data on the Soviet military stuff. Perhaps the difference is simply in test barrel length.

The case volume difference certainly isn't enough to account for it.

I have a friend who's shot many rounds of 7.62mm NATO and .308 in Mosins, with a piece of sticky backed foil around the case ahead of the extractor groove to take up the space. I haven't yet tried it, but have some of the sticky foil and plan to. He says it'll extract well enough without a rim to get the cases out by hand, but it won't eject reliably. It seems to be a fairly well known trick. A friend of my friend showed him a 7.62x51 fired case with sticky foil around the base just like he'd been using, picked up from a combat zone in Bosnia.

02 September 2004, 17:29

denton

Quote:

Ackley was using lead cored, copper jacketed bullets. Many bullets for the 7.62x54R have mild steel cores, a thin layer of lead over that, and a copper washed mild steel jacket. I'd be more leery of shooting these through bores much undersized.

Yup. Lots of people do shoot the steel stuff. It's something to take into consideration.

I'd be a bit worried about using the Mosins at 308 pressures, though. Based on the data I could find, the max peak is around 52-55 KPSI. If memory serves correctly, the 308 is good to 62 KPSI. And the Mosin seals on the rim.... Yikes! No rim on the 308.

At 51 KPSI, I get 2640 fps with 180 grain bullets... not too shabby. I could probably wring another 100 fps out of it, but why?

03 September 2004, 04:07

<eldeguello>

IF you don't think the .308 is "right there with the .30/'06" also, you are very much mistaken! In military loads, the two are IDENTICAL!!

03 September 2004, 05:32

Hobie

Quote:

I don't think even that is a problem, since the chamber is sealed at the rim of the case.

Do you mean that it headspaces off the rim? That would be correct. The entire case "seals" or contains the gas produced by the burning powder charge, not just the rim.
It is possible that one could have case head separation after several reloads under certain circumstances just as with the .303 British round.

Pierced or blown primers are a concern and were a big concern of early military rifle designers. That is why the ability of the action to handle gas blowing back through the action was such a big selling point and why the Mausers were constantly improved in that regard.

In Milsurps used with reasonable loads the main reason for pierced primers is damaged or out of spec firing pins not pressures or poor primer cup materials.

03 September 2004, 06:29

bajabill

are the 308 and 30-06 identical on your (or the average reloader's) reloading bench? Close, yes, within our ability to predict velocities I guess.

04 September 2004, 16:04

<eldeguello>

Quote:

are the 308 and 30-06 identical on your (or the average reloader's) reloading bench? Close, yes, within our ability to predict velocities I guess.

Over the chronograph, the '06 handloaded can beat the .308 handloaded of course, but not by much. However, if you look at the wound channels in game animals produced by the same bullet fired from one or the other, you would GENERALLY NOT be able to tell which was which!

04 September 2004, 15:56

Clark

The Mauser vents the gas to the magazine, and the 91/30 has a rimmed case for extra safety margin.
It's a trade off.