Rossi M92 problem


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MCgunner
June 28, 2008, 03:37 PM
Since I've had this gun, in .357 magnum, I'd had a problem with it cracking off cases near the rim and leaving the front part of the case in the gun on ejection. I dig it out with a screwdriver. I figured it was just old brass, nickel does it too, new or not. Nickel brass is more brittle than regular brass. New non-nickel brass doesn't do it when it's new, just as the brass gets three or four reloads. But, I had the gun at the range today and it started doing it consistently after I'd fired it enough to get it really hot. Thinking back on it, it never did it until it got hot in the past. I think what's happening is maybe the chamber is growing with thermal expansion and the brass can expand only so far without cracking. Don't affect the field use of the gun as it doesn't do it until maybe 30 rounds of rapid succession on a hot day with older brass. .38 loads don't do it, not as much chamber pressure I guess. Has anyone else noticed this in a Rossi Puma or have any wisdom to bestow me?

I got some of the best groups I've ever got out of the gun today, though. My magnum loads were shooting under 3" at 100 yards and my light .38s were shooting about 1.5" at 50, pretty danged awesome. I need to take this thing squirrel hunting. I shoot a 105 Lee cast SWC at about 900 fps for the light load and it's like shooting a .22, two guns in one. Just takes a rear sight adjustment when you switch ammo. I have a ghost ring aperture I got off an old .22 on it and it works great. Weren't for that little brass cracking problem, I'd LOVE the thing. I guess that ain't a real big deal, like I say, for field use. It has to get hot before it does it, just annoying at the range.

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rcmodel
June 28, 2008, 03:51 PM
Only two things can cause case separation in a straight-wall pistol caliber.
#1 = Excess headspace.
#2 = A rough chamber.

What is happening is, the firing pin drives the round all the way foreword in the chamber, then the case is expanding under pressure until it has a tight grip on the chamber.
Then it stretches until it reaches the breach-face, and the head cracks off.

Fixing a headspace problem would require setting the barrel back a thread, re-chambering, and then figuring out what to do about the mag-tube attachment point being in the wrong place.

A rough chamber could probably be more easily addressed with some polishing.
Perhaps with a Flex-Hone from Brownell's.
http://www.brownells.com/aspx/NS/store/ProductDetail.aspx?p=651&title=FLEX%20HONE%20RIFLE%20POLISHING%20SYSTEM

If the chamber is polished to a high finish, the case will be able to slip back more easily, without stretching as much.

rcmodel

MCgunner
June 28, 2008, 04:04 PM
Thanks, I'm thinking head space since I've polished the chamber already. It's done this, when it gets hot, since it was new. I guess as it heats up, maybe it loses proper head space as the barrel expands. Guess I'll just live with it. Like I say, really doesn't affect it for field use since it doesn't start doing it until around a couple dozen rounds on a hot day. Never done it shooting .38 loads, either.

mainmech48
June 28, 2008, 04:06 PM
rc's right. IIWY I'd take your carbine to a good 'smith and have that headspace checked ASAP. I wouldn't fire it until it'd been sorted out and vetted safe, either.

As strong as the '92 action is, I gotta wonder just what kind of loads have been through it and how many of them to get it to the point where case heads start separating.

I've run at least a couple of thousand factory-level .357 loads through mine and more than twice that number of cast bullet reloads with no sign of trouble. I've lost cases, sure, but usually after at least 5 or 6 reloadings and always to cracks at the case mouth or longitudinal splits.

I'd be very cautious with that '92 until it's fixed. Just my $0.02.

MCgunner
June 28, 2008, 04:17 PM
As strong as the '92 action is, I gotta wonder just what kind of loads have been through it and how many of them to get it to the point where case heads start separating.

See, that's the odd part. It's done this since day one. I bought the gun new about 1986 I think. I've not shot anything overly hot in it. Mostly 14.5 grains 2400 behind a Lee gas checked cast 158 SWC. I probably have between 500 and 1000 rounds of that load and a lot of .38 light stuff through it. I've never fired a factory load in it as I reload for several revolvers, too, same 158 grain load. I guess this thing must have left the factory with excessive head space.

MCgunner
June 28, 2008, 07:26 PM
I don't think it's a head space problem. I mean, I don't have a no go gauge for it, but I can stick an empty case it the chamber and force it down with my finger and the bolt seems to close tight behind it and the extractor slips over the rim just fine. Hmmmmmm.....:scrutiny: I need to find a gunsmith with a no go gauge to find out for sure, or just buy a gauge from Brownells.

Sistema1927
June 28, 2008, 08:13 PM
Steve Young (http://www.stevesgunz.com/) is the 1892 specialist.

MCgunner
June 28, 2008, 08:40 PM
Thanks. Shot him an e-m. I'd have to ship it if he works on it, long way to Port Arther from here.

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