First off, barrel dimensions have nothing to do with it's bending as it heats up. Skinny, whippy barrels will shoot just as accurate as fat, stiff ones starting cold and after 30 shots fired 20 seconds apart, still shoot extremely tiny groups. And a lot of those short, skinny sporter barrels are actually stiffer than longer, heavier ones. Good example's the original M14NM standard weight barrel; 'twould shoot inside 2/3 MOA at 600 yards shooting 25 to 30 shots in less than 22 minutes in a match. They's shoot the same in special rapid fire matches putting 24 shots down range to 600 yards in 50 seconds.
Any rifle that walks its shots as the barrel heats up does so for one or more of these reasons:
* barrel's fit to the receiver with hard contact at only one point around the barrel tenon shoulder; the receiver face ain't square with the tenon threads.
* barrel's got an epoxy pad under its chamber; as the barrel expands from heating up, more pressure's put on the barrel from underneath it and that alters how the barrel whips vertically when fired.
* barrel's not properly stress relieved or has poor metalurgy distribution in it (rarely happens).
* shooter holds the rifle differently each time it's shot as its fore end rests atop something; he keeps changing pressure against the stock in the same direction shot after shot after shot. Often happens with a pad under the barrel at the fore end's tip.
US Navy Distinguished Marksman Badge 153
Former US Navy & Palma Rifle Team Member
NRA High Power Master & Long Range High Master
NRA Smallbore Prone Master
Last edited by Bart B.; January 22, 2013 at 02:45 PM.