Thread: Winchester rim thicknesses WOW?

Retrieved: June 15, 2014
Last Post: December 10, 2006

You know it's something I never even considered before, but yesterday I took out a wack of new rimmed cases, 45/70 and 348, stood 'em up on the suface plate and gave 'em a go with the height gage... .013" difference. Don't these fellas primarily headspace off the rim? Well I guess completely in the 45's case. Man those tolerances aint great.

Bass Ackward
11-25-2006

Since a primer requires a repetitive and equal force to produce a consistent spark, what do you think that does to ignition?

Maven
11-25-2006

Charger & Bass, Now that's something to ponder: Segregate cases by weight AND rim thickness to see if the latter affects mean velocity + SD & ES and accuracy (target dispersion). On the other hand, maybe I just have too much time on my hands.

joeb33050
11-26-2006

Is this a difference of .013" in rim thickness from case to case of one type, or from 348 to 45/70?

See C. Dell's tests that show that the force of the blow on the primer doesn't affect mv. 6.3.1 in the book.

charger 1
11-26-2006

Originally Posted by joeb33050
See C. Dell's tests that show that the force of the blow on the primer doesn't affect mv. 6.3.1 in the book.

348<>348 my brother. .068 down to .055 all in the same bag... Not only is Win inferior to RP in their ability to send out unmangled big bore brass, it's not as malleable and now this. My worry was not the wack of the primer, but just how are these things supposed to headspace consistently, especially in say a falling block with no forward thrust. I would say that if anyone has a Ruger #1 in 45/70 and he's using Win brass, if his accuracy is in the crapper he may want a look at this as a possible concern.

kenjuudo
11-26-2006

Separating .22 rimfire by the rim thickness will improve groups enough to be worth the bother for target work, but not enough to matter popping squirrels.

Bass Ackward
11-26-2006

Originally Posted by charger 1
My worry was not the wack of the primer,but just how are these things supposed to headspace consistently,ecspecially in say a falling block with no forward thrust.

Charger,

In my work, when I get different hammer blow strength, I get wild ES. And with poor headspace, you need to run much faster powders to get consistent ignition or lower ES loads.

I have seen it in rifles with Savage actions where the strength of the firing pin spring is adjustable and I have seen it in handguns. When I started with my new 458X2, I was getting ES of 150 fps with a load. I adjusted the firing fin spring tighter and ES dropped to 23 fps.

I tightened handgun headspace by removing the end play in the cylinder. This holds the cylinder back against the back of the frame. It improves headspace. And this improved ES down to low double to single digits in that gun. 44man has written here of changing hammer springs on his handguns just to get accuracy to come back.

So consistent firing pin blow that starts with headspace is everything to consistent ignition. If you don't hold the cartridge case, and thus the primer in the same location every time, how can you possibly be getting the same ignition?

drinks
11-26-2006

Rim thickness is not the only variable, I once measured 10 different cases, all for large rifle primers, and the depth of the pocket varied from .124" to .138", .130" is the height of a large rifle primer.

With this, you can run from slamfires to misfires, depending on the length of the firing pin, amount it protrudes and where the stop is adjusted to.

Bass Ackward
11-26-2006

Drinks,

Absolutley. I forget to consider that because my pockets are uniformed as a part of the "new" brass ritual.

We tend to over look the stuff "we do" when we are on autopilot. Good point.

six_gun
11-28-2006

I had a problem with some new Winchester brass and misfires with my Hornet barrel on my Contender. I traced it to the differences in rim thickness and contacted Winchester. Their solution was to attack me for not knowing what I was doing. I solved the problem with Remington brass. The rim thicknesses were very consistant and no more misfires.

Sounds like Winchester rimmed brass is still having problems.

charger 1
11-28-2006

Originally Posted by six_gun
I solved the problem with Remington brass. The rim thicknesses were very consistant and no more misfires.

Agreed Bro. Overall I'm a way bigger fan of RP brass for that and many more reasons but when your shootin' 348, you is stuck.

KCSO
11-28-2006

For serious target shooting I will start with 100 cases of 45-70 and I may get 20 matched users. To give you an idea of how much difference firing pin force will change grouping I tested a Winchester lever rifle with a rebounding hammer. Groups strung 4-6" and when the rifle was converted to a standard hammer and spring the stringing disappeared and groups shrunk to 2 1/2".

dahermit
12-10-2006

Winchester had a problem in the late 60's with a large variation in rim thickness in the .44 special. Seems as though they never cured the problem. I have found the same problem in .44 special rims from Winchester in current brass in .44 special and .357 mag.

I no longer buy Winchester brass.