I have what used to by a 700 LSS in 375 rum, I put a Timney in it, extended magazine box, and a CSR brake then dropped it in a B&C Medalist stock. The rifle shoots pretty good but the Ugly J lock was bugging me so I got online and ordered a Bolt Tool and Callahan Speedlock firing pin assembly. Initially I was a little disgusted because the shroud required a little fitting to allow the bolt down the raceway smoothly but it was fairly mild, just a little time and sand paper then steel wool to shine it back up. once I finally had the proper fitment I dry fired a couple times and could already tell a huge difference in vibration. Last night I finally got a chance to go shoot at the range. First I dry fired a few times and the crosshairs had zero movement which was certainly different because this rifle had a ton of vibration before in anything less than a perfect rest. Then I decided to shoot a couple groups. This is where I was very impressed, it cut my groups from the .6-.7 range to the .3-.4 range. I can honestly say this was one of the best $50 I have spend on an upgrade for a 700.