Cooper Model 21 chamber

[Travelor]

I have what I believe to be a early Model 21 (SN is two letters followed by 2 numbers) chambered in 204 Ruger. The fired cases, both factory and reloaded, show a pronounced expansion (.005" greater than a case fired by a Remington 700 in same caliber with ammo from the same box of ammo) at the "pressure ring" or just about 1/2" from the rear of the case.

Anyone notice this in their Cooper? If so what if anything have you done about it?

Thanks,
George

[SShooterZ]

Tighter chamber in the Cooper resulting in higher pressure would be my guess. That's not a bad thing IMO.

[Rick in Oregon]

Humm, almost sounds like a possible dull, wandering reamer, but to be certain, the only way to tell would be to send it back to Cooper and have them make a chamber cast to see it the end of the chamber is slightly oversize.

My Cooper MTV in 204 when brand new was smoking cases (only WW), so sent it back and got a chamber cast done while there. Found the neck I.D. was .234" and NOT the .232" dimension everyone thinks their chamber is cut, and found the smoking case issue was only with new WW cases; all others did not exhibit this issue and it hasn't done it since new.

I'd give them a call, see what they say and maybe just send it back to give you peace of mind and get the issue resolved.

[Jim White]

I'll add; if you need to sendit back and do not have the factory boxes they will sell them to you for about 20-25 dollars as I recall. They are a box-in-a-box complete with the foam cut out.

All in all, they're good folks to deal with.

[Travelor]

Rick and all, were your cases showing the bulge mine are at the pressure ring?

[Rick in Oregon]

Rick and all, were your cases showing the bulge mine are at the pressure ring?

No, other than the smoking of cases, all brass dimensions after firing were 'normal'.

[Travelor]

I have a M21 Varmint Cooper in 204 Ruger. The fired cases, both factory and reloads show a pronounced bulge at the "pressure ring" of .005" more than my friend's Remington 204 Varmint.

The pressure ring expands from a FL resized diameter of .370" to a fired diameter of .380". Also the necks of the cases expand from loaded diameter of .227" to a fired diameter of .233". Accuracy is spotty!!!

My questions is, "Is the chamber on this rifle over sized?

I believe I know the answer, but I thought I would ask your opinions.

[Travelor]

Gun went back to Cooper who found barrel to need replacing. As they had no 204 Ruger barrels in stock, I was told 8-12 weeks, It's been gone about 5 weeks now. Time goes so slow when waiting and so fast when your not...............

[Rick in Oregon]

Well, look at it this way; when it comes back, you'll basically have a brand new rifle with a zero round count, and being a replacement barrel, I'm certain they'll take great pains to ensure it's a good one for you.

That's a bit of a wait, but it will be well worth it in the long run, plus the peace of mind knowing that it'll be right with no worries. While you're waiting, you'll have time to get all that 204 brass prepped and ready for testing in the new barrel.

[wirelessguy2005]

did they ever give you an actual answer as to what the problem was? As Rick mentioned in an earlier post it sure sounds like they have a problem with the reamer wandering. I bought a rifle a couple years ago that was supposed to be in like new condition and just rebarreled, when it arrived i was inspecting a few pieces of fired brass that came with it and found it to be belled out a good 5-6 thou in the same spot that you are talking about. I believe the reamer was wandering or the gunsmith was incompetent. Either way it was not good work and never should have made it out of a gunsmith's hands or the Cooper factory in your case.

Gun went back to Cooper who found barrel to need replacing. As they had no 204 Ruger barrels in stock, I was told 8-12 weeks, It's been gone about 5 weeks now. Time goes so slow when waiting and so fast when your not...............

[Travelor]

Not yet, but I will get an answer especially if they want money to replace the barrel. I suspect the wandering reamer is the answer.

Now having problems with the brass I fired in the gun fitting the chamber of a custom build 204 Ruger even after FL sizing the brass. Looks like I need a small base sizer to "reclaim" the brass if shot in the new gun.

I'm about 5 weeks from sending the gun in to Cooper.

[wirelessguy2005]

if the brass won't chamber after full length sizing I would say you have an excessively oversized chamber most likely. If it was me I would scrap that brass and start over with new, of course you might ask Cooper to pay for replacing the brass as well.

[Travelor]

Gun still at Cooper and latest communication tells me the wait time for them will be 16 weeks to get the barrel then shop time to chamber and fit.

I am getting VERY unhappy............................................

[RAMOS]

Hang in there, good things come to he who waits. Think I got that close to right...

[Travelor]

Thanks Ramos, hope so.

I bought the gun used over the internet with a Zeiss Conquest scope for a very good price. Very nice wood and great scope.

Guess the prior owner found the same problem and passed it along to me with no warning. Still believing when I get it back it will be a great shooter.