Need help resolving a 1903's insufficient headspace

[1903Collector]

Jim, I defer to your broader experience. I speak only of the 1903, and frankly, to the best of my knowledge, the M1 Carbine, Garand, M1918, M14 and pretty much any other smokeless powder Military long arm from any primary combatant of conflicts involving the U.S. I have little practical experience with "modern" bolt action rifles.

I do have a question of the practice though. Im unsure of the typical barrel thread pitch, but unless the pitch is super-fine it would not take much rotation to set the barrel head back quite a bit. Considering the very small difference between "GO" and "Field" gage sizes Im surprised there are chambers cut so short as to require more than just a little headspace reaming. When I cut a short chambered 1903 barrel I have to be VERY careful not to take too much off. I confess with some chagrin that Ive ruined a number of barrels when I cut the chamber too deep with what seemed to be just a turn or two of the reamer. Is rotational alignment not required in such barrel/receiver designs that you are familiar with? If there is no barrel shoulder to compress against the receiver face how can the correct torque be set?

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[ssgross]

Im unsure of the typical barrel thread pitch

Square threads on the 1903, 10 per inch I think, with grooves at 0.051 wide. Yes. google doesn't lie

When I cut a short chambered 1903 barrel I have to be VERY careful not to take too much off.

even more careful on an old barrel that appears to be short. Even just a little leftover jagged edges from surface rust on the chamber's shoulder can throw off your go gauge. On new short chambered barrels, it usually takes me 5-20 turns. As such, I make one turn without any downward pressure just to clean out any possible edges left by the rougher, then I take it 2-3 turns at a time with very very light pressure. There is no reason to press down noticeably when finish reaming by hand. Use plenty of cutting oil, clean everything out every 2-3 turns when you check your progress.

setting a 1903 barrel back would require a full turn taken off the shoulder (so ~0.100), and then the same amount taken off the breech face, extractor groove deepened, etc.

[browningautorifle]

If there is no barrel shoulder

There should be a shoulder. I can't picture a military barrel without one, nor a civilian barrel presently. If no shoulder then it would turn against a ring inside the receiver, or like the Lee Enfield, both.

it would not take much rotation to set the barrel head back quite a bit

When you talk about setback, you talk about it in a complete rotation, usually. If it were certain civilian rifles with rapid taper and unmarked barrels you could get away with less. It takes a minute to figure out how much to machine off the shoulder to give one turn to TDC.

Ive ruined a number of barrels when I cut the chamber too deep

You wouldn't be alone. Very, very careful. Last M1 rifle I did was a .308 barrel and it took so long with a breech end ream...but turned out perfect and tight.