Post
by TwoRivers » Wed Sep 07, 2011 9:55 pm
Ashok: Yes, the M1917 was the British P1914 adapted for the American .30-06 cartridge, Still, the five-groove rifling was retained, dimensioned for .30 caliber. Rifles rebarreled during WWII can have four- or two-groove rifling. The actual bore dimensions for the Springfield rifle were .2995-3015" bore, .3075-.3095" groove diameter.
The point I am making is this: Gauging with a bullet of unknown diameter in this case only tells you that the IOF rifle has a tighter muzzle than the Enfield. It tells you nothing of the actual bore dimensions of either rifle, or the actual diameter of the bullet at the point of contact. You can not assume, that the diameter of the bullet were it contacts the muzzle is .308"/7.82mm. As I mentioned, bore wear at the muzzle comes from improper cleaning. If it causes inaccuracy, it can be easily remedied by counterboring the muzzle by one to two inches. In any case, whether the apparent wear affects accuracy can only be determined by shooting. To get an idea about the barrel, absent proper gauges, it shoud be slugged with a soft lead ball, then carefully measured with a micrometer. With five grooves it requires a special gauge block to determine actual bore and groove diameter. But the condition of the bore will still be apparent.
I am familiar with the book you mention, and don't have a very high opinion of it. As my grandfather used to say, "paper is accepting". You can write anything on it, true or untrue, factual or erroneous. Books like Smith's are usually for ''general consumption", not very carefully researched, nor written by the truly knowledgeable. Cheers.