I load copper bullets for two rifles my 375 Ruger and my sons 22-250 I use GS Custom bullets which are pure copper but with their design of drive bands they they don't seem to leave a copper buildup in the bore and I have recovered many of them from the back stop with no sign of erosion of the copper. I have also noticed that heat build up in barrels is less than other bullets especially in my 375. The hardest thing to accept was the fact that they recommended bullets that were light for caliber but after a few emails and a couple phone calls I decided to try them. Sorry to say that the 375 did not get a chance to harvest any game but my sons 22-250 with 40gr HV took two deer the first at 172 yards the little bullet moving at 4175 at the muzzle entered just behind front shoulder taking out 1 lung then into a full stomach and intestines and exited in front of hind leg on other side. That little bullet penatrated almost 23" of deer before it exited. The second was a broadside shot at 220 yards another complete pass threw. In both shots the 375 was on the animals because I was a little concerned about bullet performance but in both shots it was unnecessary. In comparison the 40gr HV is slightly longer than a 55gr cup and core bullet and 200gr HV is longer than a 250gr game king. I know that two shots does not make a complete test but so far so good.