santacruzdave
Member
Finally got around to slugging my 9mm pistol barrels. I'm not all that experienced reloading and I wanted to gather some information on why some of my reloads are way more accurate than others. So I slugged the bores of my 4 pistols and wound up with 2 measuring .3565 and 2 measuring .3545.
I shoot coated lead bullets primarily. Dug thru a few manuals and found the following recommendation for accurately sizing lead bullets in the Lyman 50th Edition reloading manual, "If the first tests [bullet diameter = bore diameter] do not provide the desired accuracy, a second series of attempts can be with bullets sized 0.001" larger. A third sequence can be with bullets 0.002" larger. It is counter productive to use any larger sizing diameter."
Lee's Modern Reloading 2nd edition does not recommend (that I can find) a specific size range as the Lyman manual does. Lee does state that "The problem of excessively large bullets is not exactly what one would expect." Lee goes on to explain that these large bullets will not cause excessive pressure, but will cause chambering problems especially with cases that have thick walls. So it appears that bullets so large as to cause excessive pressure would cause the case to become too large to chamber, and therefore the problem over pressure with oversize bullets is self eliminating.
My most accurate coated lead handload to date is a 122 gr ACME Truncated Cone, COL of 1.040, over 4.5 gr of CFE-Pistol shot out of a CZ SP-01 with a slugged bore of .3565. I measured the 122 gr ACME at .356. The attached photo is 50 rounds of this load shot at 10 yards off hand. I'm happy with these results.
Would you call this good? Do you think it would be productive to experiment with a slightly larger bullet, say a .3570. Have you slugged your barrel and did you find one size bullet to be more accurate than another?
I shoot coated lead bullets primarily. Dug thru a few manuals and found the following recommendation for accurately sizing lead bullets in the Lyman 50th Edition reloading manual, "If the first tests [bullet diameter = bore diameter] do not provide the desired accuracy, a second series of attempts can be with bullets sized 0.001" larger. A third sequence can be with bullets 0.002" larger. It is counter productive to use any larger sizing diameter."
Lee's Modern Reloading 2nd edition does not recommend (that I can find) a specific size range as the Lyman manual does. Lee does state that "The problem of excessively large bullets is not exactly what one would expect." Lee goes on to explain that these large bullets will not cause excessive pressure, but will cause chambering problems especially with cases that have thick walls. So it appears that bullets so large as to cause excessive pressure would cause the case to become too large to chamber, and therefore the problem over pressure with oversize bullets is self eliminating.
My most accurate coated lead handload to date is a 122 gr ACME Truncated Cone, COL of 1.040, over 4.5 gr of CFE-Pistol shot out of a CZ SP-01 with a slugged bore of .3565. I measured the 122 gr ACME at .356. The attached photo is 50 rounds of this load shot at 10 yards off hand. I'm happy with these results.
Would you call this good? Do you think it would be productive to experiment with a slightly larger bullet, say a .3570. Have you slugged your barrel and did you find one size bullet to be more accurate than another?