M1 Garand - Head Clearance

[MtnCreek]

I'm looking for advice re setting cartridge head clearance for an M1 Garand.

What is the proper method for determining cartridge headspace?

Is there a generally accepted head clearance measurement? Do most setup their die w/ a tool like sinclair/hornady or a gauge?

Thanks.

 

[Dstoenner]

You are conflating 2 concepts. Headspace is measured from bolt face to shoulder and is checked with GO and NOGO gauges. That is setup by the person reaming the barrel and once set it is never messed with.

The other question was determining the place where a bullet contacts the lands. For that you use the any number of devices along with a sample bullet.

Unless You are going to single load every round you are limited to around 3.340 for a max length regardless of bullet. That is the mag length. It actually will allow a “little” longer but then you risk a jam.

David

 

[FLIGHT762]

For my M-1's and M-1A's, I set my F/L die to resize case shoulders @ SAAMI minimum. The issue when using a shoulder datum comparator like the Hornady or the Sinclair is determining what number is SAAMI minimum on the comparator. What I have done is taken a standard headspace Go gauge and measured, noting the numbers, which will be SAAMI minimum. An example is my Hornady .400 insert reads 1.621" on a 1.630" 308 Go gauge. So when I measure my resized cases, 1.621" will be SAAMI minimum.

You can measure the shoulder off of a factory round, but factory ammo shoulders can be a few thousandths shorter than SAAMI minimum.

A drop in gauge will also work like the Wilson, Sheridan, etc. With those kinds of gauges, you set your F/L die to set the shoulder to have the case head even with the lower step in the gauge. They can be finicky when you get a bent case rim, it can give a false reading, but they work to set shoulders to minimum.

I like the Hornady style comparators since they will give you hard numbers to exactly where you're at.

Usually case life in these rifles aren't very long. A lot of reloaders use the cases 5 or so times and retire the case.

I have found this works for me and gives reliable chambering.

 

[smoothy8500]

What is the proper method for determining cartridge headspace?

There are methods to adjust the cartridge sizing by using feeler gauges and the stripped bolt to determine cartridge headspace. In all practicality what @FLIGHT762 wrote is fine. Getting an exact measurement can be affected by bent rims which is quite common on Garand brass and becomes an exercise in futility trying to do an exact .003-.004" shoulder bump.

 

[rweaver00geo]

if im understanding the question right, When I reload for the Garand on a single stage I would set up your die with full contact of the shell holder to the die + some cam over. I have a drop in gauge that I spot check with ....and begin