GI Throat Erosion Gage for the M1917

[45B20]

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 Dick is also listing TR gages. Canfield also??? And I would think that the Stone Axe M1903 T.E. gage, will work just fine.

45B20

Information

Warning: This is a relatively older thread This discussion is older than 360 days. Some information contained in it may no longer be current.

[Chuckindenver]

says on the gauge, rilfe cal, .30 and machinegun cal.30.
stone axe makes a nice one as well.

[45B20]

Chuck
Well, not exactly, mine has stamped on the handle part, “GAGE BREECH BORE TAPER CAL..30 C-3940” and stamped on the other side of the handle is “ILLINOIS GAGE CO..”. On the actual measuring part that attaches to the handle, on the first part, it is marked “MACH. GUN CAL. .30”, then on the upper part “U S RIFLE CAL .30 M1903 A1”. I am not sure if this is the same marking on all C-3940 (TE) breech bore gages, however other than manufacture it is the same that I can remember. Do you know of any other markings??? A few of the C-3940s had 8 measuring marks (manufacturing error) most had 10. For a gage collector one of the ’8 measuring marks’ C-3940s would be a real find.

I think it was Rick, who said that the 03 Stone Axe Gages were no longer available, do you know if they are or/not ??? I thought they were the best non GI gages.

45B20

[Chuckindenver]

what do you meen,{not exactly} the gauge pictured is the exact TE gauge you wrote in your posting, it is a GI .30 cal rifle TE gauge.
cant get more GI then that.
i dont know if stone axe still sells the ones the made, i only use GI gauges.
i looked into having this one duplicated, at 120.00 each, it wasnt a deal i wanted to venture into.
FYI: many companys made tooling for the military, B&S, Hadley spec, tool, ect.
mine doesnt have a manufactures mark, but is a GI tool.
and it does work with both 1903, and 1917 rifles.
likely your was made after 1926 when they started with the 1903A1 rifles.
most replacement parts, and tools made for the 1903 were listed as 1903A1.
even though the C stock wasnt ever installed on a combat issue 1903 when new.
the only 1903 service rifle variant issued new with a C stock was the 1903A4 snipers rifle.
and that gauge will work on 1903, 1903A1, 1903A3, 1903A4 and the M1917.
as well as the Browning 1919 MG. with the barrel removed.
you can gauge the barrrel on a bolt action with the barrel installed and seperate from the receiver.

[Bill Ricca]

Many people are not aware that the gage readings were not accurate/important on new barrels manufactured after 1942.

There was a problem with projectiles getting stuck in rifling when unloading live ammunition, which led to a deeper rifling start in 1942. All 30 caliber and 50 caliber barrels were changed.

Here is the article, which, unfortunately also refers to the Garand gage C64343 as 03.

[Chuckindenver]

great info Bill, thats one reason, i finish ream to a commecial loaded round, and not a GI round.

[Jeremy]

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.

Sorry to dig this up.....BUT..

Is the gage read the same way as on an M1903 or is it different?

Thanks!