Q: I read in a well known text that when the British P-14 Enfield rifle was converted from .303 British to .30-06 and manufactured as the U.S Model 1917 that the bore and rifling was left unchanged. Now, I’ve been told that this is incorrect. Surely bore and rifling would have been badly oversize enough to cause inaccurate shooting with .30-06 ammo, to say nothing of increased erosion due to gas blowby. Can you tell me whether the bore and rifling dimensions were changed or not?
Pat Donovan
A: Commonsense should tell you that they were changed. However, I’ve also seen it repeated in print that the original .303 bore and rifling were retained. This impression may have been due to the fact that the .303 style of rifling consisting of 5 lands and grooves of equal widths, really was retained. But to accommodate the .3085 diameter bullets of the .30-06, the bore was reduced from .303 to .300, and the groove depth was also reduced. The M-17 had a slightly greater depth of groove than in the Model 1903 Springfield, which has nominal dimensions of .300″ bore and .004″ groove diameter. But the Springfield rifling lands are narrow, only 1/3rd as wide as the grooves. This is all explained fully in Chapter II of Hatcher’s Notebook and it also mentions the fact that M-17 barrels regularly outlasted the 1903 Springfield ones.
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