I shoot on a somewhat primitive range with no cover from the sun (no benches or target frames either, (had to build my own portable setups). During hot summer days here in central Georgia, my barrel (especially blued ones) can get too hot to touch just sitting in the sun let alone being fired. I've see groups open up shooting a magnum with a factory blued sporter barrel after just the first three shots and continue to get bigger after subsequent rounds fired.

What 82boy says is most likey true to a great degree. I can't argue with him as I've never shot a sanctioned benchrest match on a nice range. What I do know is MY accuracy is affected by a hot barrel whether it's a fault of the hot sun or X number rounds through the barrel or possibly a result of the combination of conditions. Obviously, barrel life for match shooters can be short because of barrel heat in a match and not rate of fire. It's no wonder some barrels are no longer competitive in as little as 800 rounds.

I can't afford to replace barrels often so will stick with letting my barrels cool as best they can considering my conditions.