I have the Steven Mathews gauge for 1903 (there was an entity called Stone Axe engineering he was part of or ran but no longer, its purely Steve only) .
Discussing with him on how it applies to the 1917 and he says the MW is spot on (within the gauge accuracy limitation) and the TE is pretty close but not calibrated to a 1917. He is not in the greatest health and does runs of these as he can.
Its a nicely done setup in as it combines the MW and TE in one gauge (also M1 and M14 versions available)
I do not have any interest in Steves work other than appreciate for a low cost tool that does what I needed so I am not in any way benefiting from passing this information on.
Cost is $54 I believe and that include shipping.
Its not a military precision gauge, maybe more precise than some of the suggestions here but Steve specifically lists it as a hobbiest gauge so its an indicator not absolute spot on definitive.
Accuracy is .005 per his statement and accuracy ability in making these.
If you are into these I think its a worth while investment, I carry mine to all gun shows and any LGS I am at as it provides a pretty quick assessment of what I am looking at and for.
Its also resolved some internet purchase questions, one in particular was a 1917 barrel that the TE was really bad but the MW was good (blanks probably shot through it as that is a signature of that type)
Steves email is:
fatmatthews2@hotmail.com
His mailing address is: Steven Mathews - P.O. Box 125 - Scott, Ohio 45886