Do different brands of bullets copper foul barrels more than another? Does temp effect copper fouling in a barrel in colder weather? The reason i ask is that i shot all spring and summer an into to early fall and not much copper fouling. Shot more than 300 rnds in .243 and not any noticable copper fouling. Cleaned bore out in the warm weather after 30 rnds. Pathces came out with some blueing but not much. Also could not see copper fouling in the barrel.Then winter came and temps dropped. Did some new load development in the winter after temps dropped and now major copper fouling. i could look in the bore and see copper fouling. Used Hornady V max 65 gr in the warm months and ran out and only could find Nosler bt in 70 gr. Any insight would be helpful?