A while back I was having problems getting my 30 Herett to shoot accurately. I was convinced that it was due to the extremely long throat that was cut in the barrel. I tried different bullets, powders, seating depths, etc, etc. I sent a letter explaining my problem to TC and a couple weeks later they sent a set of locking lugs and a new spring. I initially thought the this was BS, but I'd give it a try, and when it didn't work, let them know.
Well I tried the new lugs and spring, and couldn't believe what I was seeing. With a less the perfect rest and shooting conditions, I was doing about 1" at 50 yards with most loads. In the past, it was like 3" at 50. I've got some more testing to do, but I think that was the problem.
When I think back I remember that when I got the barrel, it didn't lock up properly, so I stoned the lugs down until it functioned correctly. I'd heard this procedure discussed by a number of folks, as a solution for using older barrels on G2 frames. It seems like if this isn't done perfectly, you could get lousy accuracy.
So if you've got a barrel that won't shoot well, before giving up, try replacing the locking lugs.
