Thread: .45-70 headspace / rim thickness

Retrieved: June 15, 2014
Last Post: June 29, 2012

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

I believe you will find SAAMI spec at .070"

TRX
06-26-2012

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

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.

Mizura Kid
06-29-2012

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.