I am stuck at home after a surgery, thought I might add some information on the M1917. A month ago or so ago, I noticed some one stated that there were no issue Throat Erosion (also known as a breech bore gage) for the Rifle M1917. I think that this is incorrect. May I present what information I have on the subject.

There are at least three Ordnance publications that state that: the Gage, breech bore, drawing number C3940 is to be used with the Rifle M1917 and gives instructions for its use on the M1917.

“Ordnance Maintenance, U.S. Rifles Caliber .30, M1903, M1903, M1903A1, and M1917, TR 1400-30”,
10 Aug 1938, Page 21. This manual identifies this as Breech Bore Gage “as shown in drawing
No. C3940“.

“Ordnance Sergeant” Vol.6, Oct. 1943 No. 4, page 212 & 213 identifies this gage as “Breech bore gage
No. C3940.

“Base Shop Data, U.S. Rifle, Cal. .30, M1917”, Rock Island Arsenal, Feb 1943. Sheet, 11 of 13
This manual identifies this as Gage 41-G-29 which is the Stock No. for Gage drawing # C3940.
As per “Ordnance Supply Catalog ORD 6 SNL A-35, Tool, Maintenance, for Repair of Group A
Materiel” Dated 01 July 1945.

The US military use of the throat erosion gage is to give a baseline for replacing barrels when they probably are at the end of their life, but TE readings are not a set in stone thing. Barrels with reading at or near Ordnance rejection will often shoot groups that are acceptable, and will continue to do so for many more rounds. The US Army used actual firing from a rest to determine the condition of the barrel (03s &17s) until about 1935 when the gages started to become available.

TE gages are interesting, but after you have looked down at few barrels (from the chamber end), you can usually judge the condition of the barrel’s throat just by sight.

However, if you really must have a gage, someone is making a close copy of the C3940. They were listed as a breech bore gage on eBay, Brian Dickicon is also listing TR gages. Canfield also??? And I would think that the Stone Axe M1903 T.E. gage, will work just fine.

45B20
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