Checking headspace on a Ross M-10

PerversPépère

PerversPépère

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Hi!
Is the process different from an Enfield?
Given that some Rosses were field-reamed with an enlarged chamber, is the use of Go-No Go gauges for .303 British still possible? Was the resulting chamber the actual equivalent of the MkIII No.1 chamber?
PP.:)
 
As the headspace for the 303 Brit (a rimmed cartridge) is a measurement specific to the relationship between the boltface, cartridge rim and chamber face, what the chamber looks like in front of the rim is not a headspace issue per se.

You will want to dedicate brass to this particular gun and neck size regardless of the peculiarities of the chamber. You will end up with brass "correct" for your gun, but perhaps outside of specs for the 303 Brit.
 
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Nope. .303 Brit is .303 Brit. The size of the chamber doesn't matter. Slip the guage under the extractor and close the bolt. No pressure or speed required. If it closes on a No-Go, try a Field. If it closes on a Field the headspace is excessive.
Neck sizing will do nothing for bad headspace.
 
Apparently the Ordnance method used headspace gauges, combined with pencil marks on the bolt sleeve and bolt as the bolt was closed; this was because of the fact that the lugs are cut with a pitch - they don't lock at 90 degrees to the axis. Assuming that the bolt did not fully close on a Field or NO GO, the rotational amount by which the bolt did not close could be used to calculate the actual measurement . Not just a pass/fail system. The following is an excerpt from p. 209 of The Ross Rifle Story.
"...the author recommends a depth gauge measuring headspace from the muzzle. A disc 0.10" thick of a diameter of 0.50" with a hole 0.10" in diameter centrally located should be placed in the bolt head recess and then the bolt should be closed. A rod spacer, 0.25 - 0.30 inch in diameter should be inserted in the barrel , resting against the disc and extending to about 1.5 inches below the muzzle. A reading can then be taken with a micrometer depth gauge. The disc should be removed, the bolt closed, and the measurement repeated. The difference will be the true headspace....". I suppose if the rod projected from the muzzle, the measurement of projection could be used in the same manner. As has been pointed out above, chamber size and shape aren't related to headspace - but certainly could affect handloading. Segregating brass and neck sizing only may be the way to go.
 
Excellent! Thanks Tiriaq!
This will be very helpful when I try my spare bolt on that barreled action I told you about.
BTW, what should be the accepted "regulation" headspace for the 303 British in the Ross M-10?
PP.:)
 
I assume that the standard would have been the same .064 - .074 as the Lee Enfield. If the rifle has had its chamber reamed to the larger size, conventional full length resizing would really work the brass. All things being equal though, case life should be a lot longer in a Ross than in Lee.
 
Remember the specs for a MILITARY field gage are bigger than for a commercial -saami gage. Saami field is .070, Military field is .074. There is also supposedly an emergency field gage that is larger yet, but I have never seen one.
 
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