Re: 264 Win Mag can some one explain why it flattens boat tails?
"overbore" doesn't mean high pressure. You can of course load any cartridge to give excessive pressure. That's dumb as doing so will damage the action. At reasonable pressures however an "overbore" cartridge will give reduced barrel throat life. Throat erosion takes place as the temperature of the surface of the metal in the barrel throat approaches the melting point of the barrel steel. That's primarily a a function of the bore diameter (normal) , the pressure (and hence the temperature) of the propellant gas (normal) , and the duration of the propellant flow which will be longer than cartridges with smaller case capacity. . I can't think of any reason a 264 WM should damage boattail bullets, and I've never seen evidence that it does in the bullets I shoot. I'm not saying it can't happen. I'd like to see photos of the recoverd bullets. It might tell if the damage was from pressure, jacket melting, or the result of impact at the target.
Some other "overbore" factory cartridges include the 223 WSSM,, the 7mm Rem Ultra Mag and the 30-378 Weatherby Magnum. There are a number of severely overbore wildcat cartridges. I own two 264 Win Mags. One is a pre-64 "featherweight" Win 70 with a 22" barrel The other is Rem 700 F Class target rifle with a 28" Pac-Nor heavy barrel. They are as different as night and day in their characteristics.
The only thing wrong with overbore cartridges is reduced barrel life. Why own an overbore rifle? It's because they can have superior performance in windy conditions with low drag bullets. Smaller cartridges (or larger bores) are usually superior when wind deflection uncertainty is not the limiting accuracy factor. Personally I don't mind buying barrels occasionally to get high performance. Barrels are not the major expense of shooting a 264 Win Mag or a 223 WSSM or a 30-378 Wby. Ammunition is even if it's handloaded.
Last edited by LouBoyd; 08-15-2011 at 10:40 AM.