I want to pass on a bad experience my son had with his Remington model 600 in .243. We were at the range and I surprised him with several boxes of Winchester's 55 grain Ballistic Sivertip cartridges. They have a published muzzel velocity of over 4000 fps! We thought these would be really fun to try out. Well they didn't shoot to the same point of aim as the rounds he had been using. There was a big difference. We fired several rounds getting the scope adjusted for them. Then over the course of a couple of hours we fired the remainder of the first box of twenty and then a second box of twenty. The gun heated up in just a few rounds so we paused for about ten minutes between each string of three or four shots - definately not rapid fire. We noticed that we were having a difficult time getting it to group. Grouping became more and more difficult until we realized that the rounds were now creating an erratic pattern on the target. I'm talking six inch groups at 100 yds. This rifle had regularly fired honest 2-2.5 inch groups before. After firing the final of a total of forty rounds, we decided to stop and take a good look at the bore. Yikes. The riflling was now just a bunch of rounded off ridges and we could see marks that appeared to indicate the bullets had been jumping the lands and grooves on their way to a more direct exit out the barrel. The barrel was worthless. Forty rounds of that ammo had taken a really nice bore and wiped it out. Only fourty slowly fired rounds.
I was lucky to find a "like-new" barrel in .308 and I had a gunsmith replace the barrel for him. Nice gun, nice caliber, but beware of the ammunition.