Headspace Check Procedure

[RCK]

I seem to remember that special precautions must be taken to check the headspace on Model 1917 rifles. It seemed to have something to do with how the bolt locking lugs were machined. Let me know if I am having a senior moment and if not, describe the proper procedure to use, I have all the 30-06 headspace gages. Thanks, from a definite "senior".

[Cosine26]

M1917 Headspace Measurement
In past posts I have seen several discussions concerning measurement of headspace in a M1917. This has been the subject of continuing discussion for a number of years. Excessive headspace of M1917’s was discussed after WWI when the M1917 was released for sale and again after WWII when the M1917 was again released for sale. The M1917 bolt lug design differs from the M1903, M54, M70, M98, etc. Rather than trying to discuss it as an amateur, I researched the matter and found the opinion of an expert. Remember that after WWI Remington used “left over” M1917 action to create the various versions of the Remington Model 30 rifle. The bolt and receiver of the M30 with cosmetic modifications duplicates that of the M1917. The question arose when an attempt was made to measure the headspace of a Remington 30 using a cartridge and some metal shims. Using this method it was determined that the headspace of a Remington 30 was excessive. The rifle was returned to Remington and was found to be well within spec. The following is a letter from the Works Superintendent of the Remington Arms factory. This information comes from “The Dope Bag” appearing in the AMERICAN RIFLEMAN magazine for February 1934, p 32. I quote as follows”
“A review of the correspondence between yourself, Mr. Hadley, and others Indicates that your method of headspace measurement is with a cartridge or dummy cartridge and shims of known thickness. In view of this procedure of headspace measurement, we wish to call to your attention to the locking cam arrangement of our Model 30 as compared to the locking cam arrangement of the Springfield. Figures which are given below are approximate but are sufficiently close to demonstrate the comparison.
“In the Springfield the bolt lugs ride the locking cam having a lead of 1.5” per revolution, through a swing of approximately 37 degrees, after which the flat rear face of the bolt lugs contacts the flat face of the locking shoulders of the receiver.
In the Model 30 the bolt lugs ride a lead cam having a lead of 1.5” per ‘rev’ through a swing of only 20 degrees, after which the ‘cam-cut’ rear faces of the bolt lugs contact the locking cams on the locking shoulders of the receiver and move through of a swing of approximately 70 degrees on these locking cams, which have a lead of 0.14” per ‘rev’. The power of the locking cams on the Model 30, as compared to the locking cams on the Springfield may be said to be in the ratio of 1.5 to 0.14; that is the power of the locking cam on the Model 30 is 1.5/0.14 or 10.7 times as much as the power of the locking cam on the Springfield. In other words, on the Model 30 rifle to close the bolt against resistance requires a force approximately one tenth of that required by the Springfield
“This proposition may be stated in a different manner as follows:
“The Springfield has a lead cam of 1.5’ through a swing of 37 degrees and no locking cam.
“ The Model 30 has a lead cam of 1.5” lead operating through a swing of 20 degrees and then a locking cam of 0.14” lead operating through a swing of 70 degrees.
“In the Springfield the bolt swings through approximately 37 degrees on a 1.5” cam to get to the limit of full forward linear travel. The remaining swing of the bolt in the closed position to its closed position is on flat surfaces of bolt lug and receiver and there is no forward travel after completion of the 37 degree swing
“In the Model 30 the bolt swings through approximately 20 degrees on a 1.5’ lead cam and then through 70 degrees on a 0.14” locking cam to get to the limit of full forward linear travel.”

There is further discussion in which Mr. Brown states:
“We believe the power of this locking cam to be an advantage in the use of the gun, since it provides considerable power to close over a cartridge which may be mutilated or too long. We believe also that the locking cams on the Model 30 permit easier opening after firing.
H.A. Brown”
* I realize that this is a long discussion, but I think that it points out how incorrect headspace measurements can be made in the M1917/M30 type of action. The bolt should be stripped and only light finger pressure exerted when measuring headspace.
Hope this is informative
Rather long but hope it helps. Since Rem 30 and M1917 are one and the same, this applies to the M1917.

[chuckindenver]

remove your cocking assembly,
insert the tool, lightly close. felt resestance on the tool is pass..flopping down easy is a fail.

[swede49]

I have two Eddystone M1917 rifles, both 1918 dates, one headspaces while the other does not. The one that does not came to me with a United Shoe (usmc) bolt. I bought a stripped Winchester NS bolt that appears to be brand new or NOS, with 100% blueing and zero scratches/dings/visible wear--BINGO--field gauge doesn't come near closing, while closing on unloaded dummy round.

:headbang::headbang::headbang:

[fguffey]

I have two Eddystone M1917 rifles, both 1918 dates, one headspaces while the other does not.

All of my rifles with chambers head space, I have one Eddystone that has a chamber that is .002" longer than a field reject gage, the chamber is .011" longer than a go-gage length chamber. I could say the chamber is out of SAAMI specifications if I compared their + and -, basic and general description of specifications.

It is nice to know if the bolt will close on a go-gage, problem, a rifle with a no-go or field reject length chamber will also close on a go-gage. I want to know the length of the chamber from the shoulder/datum to the bolt face in thousandths. I form 280 Remington cases to 30/06 cases, to accomplish that I have to know the length of the chamber from the shoulder to the bolt face.

For my Eddystone with the long chamber I add .014" to the length of the case from the shoulder to the case head. I could fire form, I choose not to.

F. Guffey