View Full Version : Bore diameter slug test on my 30 cal rifles

02-25-2007, 9:18 PM
I put a "how to" question in the C&R forum a few days ago and having today slugged 4 C&R rifles and 2 modern 308's, I thought the method and results might be useful to general forum. My original intent was to see how good/bad a shape those mil surp bores were, and if I could use the same bullets to reload both my Enfield (303) and my Mosins (7.62 x 54 R). I already had a good set of digital calipers. So the only "new" tools I needed turned out to be a 59 cent oak dowel (cut down to 10" pieces) and a package of 99 cent fishing weights.
I tried slugging my 1891/38 first because I was least concerned about damaging this gun. It turned out the bore was so large the 1/8 oz 0.312 egg sinker almost fell right through the barrel. I went back to Big5 fishing dept and got some of the "30 cal lead rifle" sinkers. These worked great. I had to use the 1/4 oz. for the C&R but 3/16 oz. worked fine for my modern 308's.
It turns out my 1891/38 was "worn" a lot. Besides just the final numbers, one also gets a feel for what is going on in the length of the barrel. The M38 would go loose then tight then loose several times down the barrel. The M30 was progressively looser the farther from the muzzle. All other test guns were tight the whole way. A table of results shows significant differences across the guns. I mic'd 4 different types of 7.62x54 mil surp ammo and they all were .310. So I can pull these a reload for my Enfield. Answered my own curiosity that standard 308's would be too small for the Russians.
The Enfield with an odd number of lands/grooves was most difficult to mic because groove/groove or land/land was not 180 apart (why those Brit's have to be odd). I wonder if the better quality bore of the M30 was that it was made 1939 early in the war before panic mass production mode like the 1944 made M38?