M1917 Headspace Question

[swede49]

My Eddystone 9-18 does not pass the field gage test using a Forster gage, which is SAAMI spec. Is that the final authority, or is there a military spec for these old rifles? I have fired it, and was pleased with results.

[kcw]

I would assume that the GI gauges for both the 03 Springfield and the 1917 are the same? GI gauges for the Springfield are 1.940", 1.946" & 1.950". "The 1.950" is used in the field, and the 1.940 & 1.946 are used for testing in the arsenal or depot." (As per TM9-1270)
Info I've seen says that the 17' bolt needs to be stripped and that a very light finger must be used when closing the bolt on the gauge.

[Dan Shapiro]

"Info I've seen says that the 17' bolt needs to be stripped and that a very light finger must be used when closing the bolt on the gauge. "

Don't forget, it's a Brit design and cocks on closing, so use a stripped bolt in order to get the proper feel.

[swede49]

Forster SAAMI field gage reads 2.0577, so apparently the '03 and '17 gages are not interchangeable. You're correct about the stripped bolt==force of the striker spring on closing makes it tough to feel anything, especially subtle pressure. Without stripping the bolt on a BSA #4 Mk1, I would never have felt it "pass" when testing an Okie disc field gage, it was that close. I was stunned that it passed--first and only one of my Enfields that ever did.

I guess my overall question still is: with military rifles like the M1917/1903/SwedeM96/Kar98 and others with their greater tolerances, and mauser type actions with multiple locking lugs and gas holes in the bolt and receiver, how critical is one or two thousandths of an inch? And then of course there is the question of rimmed cartridges...oy vey!

[fguffey]

“1.940", 1.946" & 1.950". "The 1.950"
“
http://www.saami.org/PubResources/CC...pringfield.pdf

1.940", 1.946" & 1.950" are measurements from the chamber body/shoulder juncture to the bolt face. When going to SAAMI measurements the first measurement as go-gage length would be 2.048, the field reject gage would be 2.058, then there is the no go-gage length that would be .004” longer than the go-gage length gage.

The Eddystone with the long chamber is not unseal, I have one that is .002” longer than a field reject gage. For me? Not a problem, I form 280 Remington cases to 30/06 with .014” added between the should of the case to the case head. The 280 Remington case is .051” longer than the 30/06 case from the shoulder to the head of the case. When forming I raise the die off the shell holder .014”, I verify the length of the case cases after forming.

Anyone that can verify the length of the case can verify the length of the go-gage or the no go-gage or the field reject gage.

Anyone that can verify the length of a gage or the length of a case from the datum/shoulder to the head of the case can measure the length of a go-gage etc. without a Hornady/Sinclair head space gage??? (comparator). I check the length of the M1917 chamber with a 280 Remington case, this method/technique allows me to to measure the length of the chamber in thousandths, meaning I do not need the go-gage, no go-gage or the field reject gage.

F. Guffey

[fguffey]

“Is that the final authority”

Final authority? I am not the AUTHORITY, I can correlate the dimensions of the chamber with the dimensions of the die with the gage. I have no problem verifying the dimensions of the gage with the case with the die.

Then there is the press, die and shell holder, because the press has threads that match the threads on the die a strong case can be made for it is safe to assume the die is adjustable. To reinforce this concept I form 280 Remington cases to chamber in the 30/06 chamber. I could mindlessly size the cases to minimum length, PROBLEM! minimum length is full length sized and is .005” shorter from the shoulder to the head of the case than a go-gage length chamber. To size the 280 Remington to 30/06 minimum length would require the shoulder on the 280 Remington to be erased and formed .051” behind the old Remington 280 shoulder.

And I ask: Why would anyone do that? With an elementary understanding of the incline plain (threads), when forming the 280 Remington to 30/06 the case will go through changes in length between the shoulder and case head, fist it gets to field reject gage length, if the shoulder is formed .004” further back it will become no go-gage length, after it passes no go-gage length it becomes minimum length.

If any thought is put into the process of case forming it should dawn on the reloader/smith the length of the chamber can be determined, in thousandths, without a go, no or beyond gage.

And as always there is the possibility of turning a go-gage in to a go to infinity gage. And it is possible to determine the length of a chamber in thousandths with a field reject gage.

F. Guffey

[Dollar Bill]

Forster SAAMI field gage reads 2.0577, so apparently the '03 and '17 gages are not interchangeable. You're correct about the stripped bolt==force of the striker spring on closing makes it tough to feel anything, especially subtle pressure. Without stripping the bolt on a BSA #4 Mk1, I would never have felt it "pass" when testing an Okie disc field gage, it was that close. I was stunned that it passed--first and only one of my Enfields that ever did.

I guess my overall question still is: with military rifles like the M1917/1903/SwedeM96/Kar98 and others with their greater tolerances, and mauser type actions with multiple locking lugs and gas holes in the bolt and receiver, how critical is one or two thousandths of an inch? And then of course there is the question of rimmed cartridges...oy vey!

1903/A3 and 1917 gages are interchangeable.

The difference is that SAAMI gages read from the bolt face to the "datum", which is where the shoulder diameter is 0.375". Military gages, as noted in Hatcher's Notebook (page 237 in my copy), measures from the bolt face to the point the shoulder measures 0.4425". Different method of gaging.

There are different measurements, but only for Garand chambers. There, they allow an extra .002.

That said, the only gages I have are SAAMI gages. These are important to use in that any ammo produced with standard dies will be to that specification. Even military ammo. The thing is, military chambers generally are longer than SAAMI specs to allow for a wider variation in ammo and dirt/carbon/junk in the chamber. One of the worst examples (as far as handloaders are concerned) is the M60 chamber. Those chambers are so long they allow the case to stretch excessively vastly reducing the number of times the cases can later be reloaded.

In the end, the fact that your rifle fails the field gage is OK as long as it's only by .001 or so. You can measure how much by using .001 shims cut to fit the boltface. The thing to remember is that upon firing, your cases will stretch a little more than normal. This is not really, in itself, cause for concern. I would check that headspace measurement periodically, say once a year or every 1K rounds to ensure it's not getting worse. If it does, a gunsmith can set the barrel back one thread and ream the chamber to minimums.

If reloading your brass, you just need to be sure and set up your sizing die so it does not set the shoulder back more than about .002 from it's fired condition. You should still get about 10 reloads from those cases (LC or HPX, not commercial) before they have stretched to far, thinning the area just forward of the web and threatening a case head separation.

[swede49]

Thanks everybody. Thought this might turn out to be one of those "wished I'd never asked" threads!!

[fguffey]

Thanks everybody. Thought this might turn out to be one of those "wished I'd never asked" threads!!

That leaves me to assume you regret asking the question. I am not a fan of 'forced conformity of thought'. I said the length of the chamber for the 30/06 chamber in the M1917 could be checked with the field reject gage, I also said the 30/06 chamber could be checked with a 280 Remington case, I also suggested a reloader with a press, die and shell holder could determine the length of the chamber by forming cases with no more than basic skills and a good understanding of the incline plain.

Stripping the bolt, cock on close, then there is pulling the trigger to prevent cocking on close.

One more time, the long chamber in the M1917 is common, one smith was blamed for the long chambers, he used a field reject gage, his skills went beyond basic, his counterparts big egos would not allow them to ask: How?

F. Guffey

[chuckindenver]

again...
on 1917 and P14s.
they have a heavy camming pressure.
with no cocking assembly, and no extractor...
it is felt restance on the tool. even if it closes on the tool.. forester Gauges seem to be undersized....and i stopped using them years ago,, G.I. guages are best...
it is common for some 1917s to have over sized chambers...more so on winchester then any others...so bad on some that case head failure is common.
short sweet...no fancy figures.... weve beat this horse with a big stick so many times...its a tender steak.