Ive shot nine deer with the 120 gr x bullets out of a 7x57 at about 2800fps, and I imagine your friend is right. At 3500 I think they would kill very quickly even on rib cage shots. They are tough enough that they arent going to fly apart like lightweight jacketed bullets at high velocity. I have seen the petals shear off on bone before, but the shank will stay intact and the nose will usually be almost double the caliber even with the petals gone. It seems to me that the x bullets kill faster with high velocity. This may be my imagination, but it sure seems that way to me. My oldest son shot several deer with 125 gr x bullets out of a 3006 at around 3100fps, and they would often drop deer shot broadside through the ribs. Ive seen the same thing with the 175gr in my 338/06. It wouldnt surprise me to see one go through a deer lengthwise, especially at 3500. In fact, its hard to stop one in a deer at any reasonable velocity. Me and my two sons have probably shot around 50 deer with x bullets and I doubt if we have recovered more than five or six bullets. I stopped a 160 gr in a buck that field dressed 190 that was coming towards me and was shot in the right shoulder, breaking the shoulder blade, cutting three ribs, went on through the guts, and lodged under the skin on the outside of the left hind leg. The velocity of that load was just 2900fps.