I received my 15/16",.50 cal, 1:70 twist GM T/C drop-in barrel this week. I had picked up an excellent T/C Hawken stock & percussion lock on ebay and since I was already very pleased with a .58 cal. Renegade barrel that I got last spring, the GM barrel was a natural choice. I also already own a .54 cal GPR so I went with the .50 for the Hawken.
Friday afternoon I went out to sight it in and after taking about 12 shots at 13 yds for the initial sight adjustment, I backed up to 50 yds. After about 20 more shots, using a .490 ball. .018 ticking patch lubed with moose milk and 70 grns of Goex FFg, I was shooting 4" groups, from cross sticks. Not the best groups, but I was shooting into a 20-25 mph gusting wind which was making it extremely difficult to hold steady on the aim. I expect that without the wind, the groups will shrink substantially.
I also tried a few shots with a .495 ball and .015 patch and that combination might be a bit more accurate, but with the wind problems I can't really say. I finished with a few shots with 100 grns of Goex FFg and it didn't seem to open up my group either. However, once again, with the way the wind was waving the barrel around, it is hard to make any conclusions. It was blowing about 30-35 mph today and is supposed to continue to be windy tomorrow, so I'll have to wait a while to really test the barrel out.
Overall, I saw enough to see that this barrel is probably going to be every bit as accurate as my .58 GM barrel, which has outstanding accuracy. From my experiences with the GM drop-in barrels, I would certainly recommend them to anyone thinking about rebarreling a rifle they will fit. It is a good thing I have 4 deer tags for this season because I now have another rifle I'm going to have to take hunting!
