Typically,oblong holes in the target.A friend and I just went through this lately.Not with a big bore but with a 22-250.He bought a Savage LRPV with an incorrectly marked barrel/box.It was marked 1-9" but was actually 1-12".With anything heavier than 60gr the target was keyholed.Being the smart guys we are,we went through a pile of 69-75gr bullets before common sense clobbered us over the head and we finally checked the twist with a cleaning rod.light bulb
The Constitution shall never be construed to prevent the people of the United States who are peaceable citizens from keeping their own arms -Samuel Adams
Last edited by Ballistic64; 06-19-2008 at 12:53 AM.
one of the better gun smiths in the 1k game told me that some were shooting an 11 twist and a couple with 11.5 using the 300smk. haven't heard of anyone using a 12 though. only one way to find out. please let us know what you find out.