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View Full Version : .45-70 headspace / rim thickness



TRX
06-23-2012, 12:52 PM
I have a No.4Mk1 Enfield I'm rebarreling to .45-70. Now I'm to where I need to set the headspace. The bolt has the usual #3 head.

"So," I said, "I'm too lazy to go dig out that box of .45-70, I'll just look the rim thickness up on the internet." And I found... chaos, with rim thickness figures all over the place.

"To heck with that," I said, and went into the other room and eventually rooted out a brand new box of unfired Remington .45-70. Applying my calipers to the rims, I found... chaos. I checked for dings on the rims, made sure I was holding the calipers straight, etc. Measuring the whole box, checking at the "-" between "R-P". The rims range from .061 to .068" thick.

I could understand some variation in rim thickness between brands, but .007" between new cartridges from the same box is crazy. Has anyone else run into this, or did I get a box made up from a bad lot of brass?

Gtek
06-24-2012, 07:27 PM
I believe you will find SAAMI spec at .070"
Gtek

TRX
06-27-2012, 12:58 AM
The SAAMI drawing is dimensioned as ".070 -.010", which isn't a format I'm familiar with. I could assume that means the same thing as .060/.070" for a min/max.

If the maximum allowable headspace is .010"... wow.

smokeywolf
06-27-2012, 02:09 AM
Without looking at the drawing. That dimensioning format would likely mean .070" is the desired dimension, with a tolerance of +.000", -.010".

Usually it is shown with the plus tolerance figure positioned above the minus tolerance figure.

I just measured 10 rounds of brand new 45-70 Starline brass and rim thickness is .064 - .066.

smokeywolf

Jim2
06-29-2012, 10:18 AM
Starlines measure 0.065 to 0.067
Win. are 0.066 to 0.068
Rem. are 0.064 to 0.068, my Remington cases seam to have the largest variations in rim thickness.

Jim

milsurpcollector1970
07-04-2012, 10:33 AM
Dont have an answer but I was planning on a similar conversion and I had some questions

what are you doing about the magazine feeding issues and how did you enlarge the torque shoulder on the receiver?

Thanks feel free to PM me I am interested in your conversion and would take any advice you would like to give