I shoot copper. However, I've had 264 cal PSP hold up to 3400.It's my understanding that with a 1:7 twist, when bullets start getting pushed to around 3200 fps & above, chances of the jacket getting slung off significantly increases. But that also has alot to do with a couple of other things. The bullet itself. A thin jacketed bullet would be more susceptible than a thicker jacketed bullet, or bonded bullets. The other thing that would make a difference is the rifling configuration. A 5R or 6 groove that's free from bore finish flaws & severe wear in a 1:7 twist would decrease the chances of slinging the jacket off of a thin jacketed bullet when pushed beyond 3200 fps.