M1917 Woes and Advice

[Cosine26]

This was posted on the old Jouster Pages, but I shall repost for info.

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

[Jim K]

A note on those gauges, as there is often a misunderstanding. Their use must be understood in terms of the tolerances of the cartridges that the rifle will use.

The GO gauge ensures that the rifle will close and operate with the LONGEST cartridge that is within tolerances for the ammunition. If, as some folks think, it denotes an absolute minimum chamber, then no cartridge longer than the minimum would fit, a bad situation unless one can tailor make ammo.

The NO-GO gauge ensures that the SHORTEST cartridge that is within tolerances will not be able to stretch far enough to exceed the elastic limits of the case material. Many used rifles will fail a NO-GO test; but as long as the FIELD REJECT gauge test is passed, there is no problem.

The FIELD REJECT gauge, which is the only one needed for used guns, is used to show that the SHORTEST allowable cartridge CAN stretch far enough to exceed the elastic limits of the case material, resulting in a case separation. If the rifle fails the FIELD REJECT gauge test, it is time to consider remedial action.

Jim

[Patrick Chadwick]

This is not my idea, someone else on one of these forums (Edward Horton??) suggested it, but I think it's great.

Take a new, fully sized 30-06 case and prime it with a USED primer. Then use a decapping tool not to push the primer out completely, but to push it back out a little way - 1 mm or 40 thou is enough.
Replace the case in the chamber. Close the bolt fully, cocking it, but do not "fire" i.e. do not let the firing pin touch the primer. Open the bolt. Remove the case. The primer will have been pushed in by the bolt face, and the case will have been pushed right into the chamber by the primer, so the primer will protrude by an amount that is, in effect, the headspace. Yes guys, I know that this is not an official CIP/SAAMI measurement, but surely it is good enough to make the judgement safe/unsafe?

Measure the protrusion of the primer. I have no idea what the official headspace for an M1917 is, so I am not going to tell you what is safe and what is not. Someone else can surely provide the values. If the value is acceptable, I suggest you fire off some factory ammo with the case type you prefer, and then subsequently use those cases, which have been fire-formed in your rifle, with neck-sizing only.

My personal viewpoint: I fire real-world cartridges, not gauges, so as long as my rifles are safe to fire those initial fire-forming rounds, then the absolute value of the headspace is academic.
Just my 2 cents, it's your rifle.

Patrick

[da gimp]

borcav, I just ordered twenty 30rd Ar15 mags from Midway, and with USPS Priority Shipping, it was a dern sight less than what you quoted as $17.00.

Call Midway now,& tell them of your problem, Larry has always made it right for us if there was any problem we had.

Have your paperwork from the order in hand when you call, and remember,
1st try to resolve an issue before opening mouth to complain.

da gimp

OFC, Mo. Chapter

[bordercav]

I wrote their customer service following my order, just because I was so mad at myself for ordering from them when there was a much more reasonable way to purchase this item. No answer! My bad for not shopping around and I'll soon get over it. The base shipping was $14 and they added an extra $3. I imagine that was a drop ship fee from Forster.

[Dan Shapiro]

As mentioned, a "Field Gauge" should be used for a rifle that's already been used. The '17 bolt, being a Brit design, cocks on CLOSING, while a US design will cock on OPENING. To use the gauge, make sure the bolt is stripped, otherwise you get no 'feel' for resistance as the bolt closes. Most of the VFW return rifles have badly pitted bores from using corrosive (primer) blanks. Mine is just a wallhanger example, it keyholes at 25 yards!

[Nugilum]

It’s back in one piece again. Here’s what it looks like:



Well guys I decided to embrace my inner idiot. I took it to the shooting range this afternoon. That first shot was kind of scary to take, but it worked like a charm.

Here’s what I did using Greek HXP 150gr M2 ball:
75 yards, test shot, and then three shot test run:


Next is 75 yards, five shot group:


Not bad for a 91 year old barrel on a CMP Salvage!

[John Sukey (Deceased)]

I simply cannot concieve of excess headspage in a P14 or M1917 as long as the bolt matches. For that matter I have 6 P14's and one M1917 and NONE of them show any signs of excess headspace!!!!