They have 2 different ones, 1 is the 270 gr that I have tested that is copper, I used a CVA MR with a .500 barrel and a Optima that had a .501 barrel, I loaded them up with a charge in both guns and turned them up side down, and used some carpet on a board to check if they would come off the powder, on the MR not enough to worry unless you would carry your gun up side down, the Optima with the .501 barrel there was a difference and you would need to check it when you got to your tree stand or blind.
Now they have a 350 gr lead bullet and so far the reviews that I have seen, not good.
If you have a tight barrel they seem to work great, My problem is, have not been able to get them to open up past 125 yards shooting 110 gr of BH 209.
To many other good bullets out there.
This is my 2 cents about them.