5 thousandths

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Blammer
Posts: 56
Joined: Sun Jun 14, 2015 2:05 am

5 thousandths

Postby Blammer » Sat Jan 30, 2016 10:32 pm

Has anyone ever heard of a rifle, semi automatic, remington 7400 in 30-06 getting locked up because the rim of a round of ammo was five thousandths larger in diameter?

I reloaded cartridge was being loaded, (self loading) after the first shot the second round jammed up the rifle.

It was reported that the case rim, was .005 (five thousandth's larger than a factory new one) and that was why the rifle jammed.

It put in the round but not far enough to get it to close up and fire, and you could not get the action open.

I mic'ed a bunch of shells, empty and full and found about that much variation from one brand and shell to the next.

Just asking if anyone has ever heard of this before.
Sometimes you have to ignore the "good idea fairy"

Please stop telling me "That can't be done" while I'm doing it, it's just plain annoying.

wally
Posts: 14
Joined: Sun Sep 13, 2015 12:14 am

Re: 5 thousandths

Postby wally » Sat Feb 06, 2016 2:33 pm

The tolerance on one of my 357Mag Blackhawks is such that Winchester brass will bind it up every time due to the rim being slightly thicker. I'm not sure how much as I measured it but but other than remembering going "huh"! I don't know what it was. I avoided Winchester brass in that gun and now with several 357's I just avoid Win Brass entirely in 357. I have not had that problem with Winchester 38sp brass though.

As for the 7400 30-06, I've never had one of those but I had a close equivalent in a 742 Woodsmaster 308. Some brands of ammo just would not feed or eject in it and it may have been most anything but rim thickness could have certainly been one of them. It was 30yrs ago but it seems to me that one of the problems was the extractor not locking over the rim and I had to pry some cases out with a small screwdriver. At the time I was not handloading so didn't pay any attention to that or what caused it, I just switched ammunition and now don't recall what type it was that wouldn't work.

Are you saying the rim is too thick for the extractor to lock over? I can buy that after my problems with the BH and Win brass. The cure might be to file a little off of the extractor. A better bet is as you have found out. Just avoid that brand of brass.

Funny until now I'd forgotten the problems with the 742 which was a reliable and accurate gun except for the problem I mentioned but I never connected it to the Blackhawk.

Blammer
Posts: 56
Joined: Sun Jun 14, 2015 2:05 am

Re: 5 thousandths

Postby Blammer » Sat Feb 06, 2016 5:04 pm

update on the story. I asked for the offending cartridge and the rest of the ammo.

first thing I did was inspect the round that was "jammed"

it had scuffs and scrapes and gouges in it that in my opinion were clearly from a dirty NOT smooth chamber. (I can only speculate on what the chamber looked like.) The shoulder had scuffs on it and deep gouges length wise, enough to hook a fingernail on them easily. I suspect it was really rusted and dirty to cause that and the base of the case, near the web had the same really bad scuff marks on it. All round dropped easily enough into my case gauge, even after being forced out of the chamber. All rounds were measured to be the exact same.

I discovered that the place "they" the "gunsmith" measured was the web area. Yes the web area was .005 larger in dia than factory rounds, but still small enough to fit in the case gauge.

So, either the chamber is cut to very minimum specs for a chamber or it is exceptionally dirty and rusted.
Sometimes you have to ignore the "good idea fairy"

Please stop telling me "That can't be done" while I'm doing it, it's just plain annoying.


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