Hey Kali - shims are pretty inexpensive and if you are ordering a spring kit you may as well get some shims too. Whether or not you need them may depend on what you find after you get your GP. As I understand it benefits are to improve alignment and reduce drag thereby making the action smoother. Helps to have a set of feeler gauges to measure gaps and apply shims where needed. I've found most of my SP and GP revolvers didn't need shims but maybe I've been lucky.
Congrats on your new GP by the way. Glad you made the plunge - you're gonna love it!
Yeah. Unless it's the last Ruger revolver you ever buy.
Shims are less than shipping and handling charges, and can be used wherever there is excessive "play" in the internal parts. They also work for all sorts of other things that use a shim. Even S&W stuff. Don't shim surfaces just because you have them, shim if parts rattle, or wear on one side and not on another, suggesting an alignment issue.
My GP100 came with a hammer with some definite play in it. It scrapped slightly on the frame. Shimming (triggershims.com) it really helped smooth things out. I also did the rest of the mods the IBOK, and went slightly lighter on the springs. The trigger is now fantastic, and I have no FTFs. I also put one shim on the trigger (it was tight), and did the hammer dog shims, as it was a little loose.
I like the shims quite well, and they are pretty darned cheap.
I have a set of shims on the way. Maybe I can get them in this weekend and report back. I can visibly see the difference in the gap(s) on each side of my hammer and see where it has contacted the frame so I know I can benefit from shims at least on my hammer, but got the other 2 sets as well. I will so a very slight polish on the internal parts using on of the popular guide lines on here since IBOK is not available any more.
2 things that have noticeably made my trigger "nicer" is shooting it(150ish rounds), with a little bit of dry fire but I have mixed feelings about dry firing it. But a little lube seemed to smooth things up a bit too (surprise surprise).