head spacing....

[rimfire]

I have to agree that using never fired brass, a small amount of excessive head space will probably never cause a concern. Where I think the danger would be is in full length sizing and pushing the shoulder back multiple times causing the area next to the web to thin with each firing. In 1903s this is particularly troubling. After the first firing I only neck size and watch my OAL and trim when necessary.

[Cosine26]

HEADSPACE NOTES
*In late 50’s or early 60’s a company (whose name I forget) manufactured for sale a head space gauge that allowed one to measure the exact headspace of a 30-06 rifle. It had a micrometer adjustable head that let one set the headspace for measurement. I do not know how well it worked for I never saw one in use. It was relatively expensive and served no better than the standard gauges. Since I have not seen it advertised in years, I would assume that it was not very successful.

*For one interested in headspace I would suggest reading the chapter on headspace in Hatchers Notebook, particularly pages 244 thru 246. General Hatcher quotes an article by Captain Melvin M. Johnson (developer of the Johnson rifle and machinegun) that appeared the March 1947 American Rifleman in which he discusses “drive in’ and its effect on headspace. There is a certain amount of “play” between where the bolt rests on the locking shoulders and where it stops it forward motion. Take your M1903, remove the firing mechanism and reinsert the bolt. The bolt can be moved longitudinally fore and aft. In the rear position the locking lugs butt against the locking shoulders, and in the forward position the bolt stops against the face of the barrel. In my S/C 03A3 fitted with a SA bolt the play is 0.014” and in my NM M1903 it is 0.015”
In his test, Capt. Johnson used a well made Mauser 98 and a NM M1903. Both rifles had a headspace measurement of between 1.940 and 1.1941. Using a carefully loaded and measured cartridge, he very gently inserted the cartridge into both actions. Careful measurement showed no change. He then chambered the rounds into each as one would do in rapid fire or for a second shot at running game. Measurement showed that the “drive in” on the Mauser was 0.0045” and on the M1903NM was 0.12”. He further indicates that the drive in automatic rifles and semi-automatic rifles is even more pronounced.

*An extreme example occurred when the Marlin Rockwell Co. adapted the old COLT (potato digger) machine gun into a model that could be synchronized on aircraft. The swinging arm was eliminated and a straight piston system was used. The “drive in” was so great that the headspace had to be reduced by 0.011”. Hatchers Notebook page 82.

*Headspacing the M1917/Remington 30 series rifles is a bit different and is the subject of another discussion.
FWIW These are not my opinions, but are the opinions of recognized experts with much experience in the firearms field.

[emmagee1917]

And , of course , if you really want to screw up your prospective , look at all the people who have shot .308 s in 30-06 chambered M1s. Usually you'll have a funny bang and a near straight walled case on the ground rather than a blown up gun. It not only has to do with excessive headspace but also where the excess is.
Chris

[RCS]

On page 140 of "The Modern Gunsmith" by James V. Howe shows the micrometer headspace gage. Must have been used before WW2. I have most of the 30M2 gages that start at 1.940, 1.941, 1.942, 1.943 1.944 1.945, 1.947, 1.949 and 1.950. I am missing a few. These are from WW2 and I have them as collectors items as they would need to be recalibrated before using them to check rifles