Actually, our group is kinda low key and we have several locally designed sporter matches involving both deliberate and rapidfire. However, we do hold a rimfire benchrest match on 3rd Saturdays and although we are no longer sanctioned (didn't want to fool with the paperwork), we still shoot by USBR rules.
As to your optics question, the Weaver T-36 is the favorite at the BR matches. One or two shooters use Leupolds. Interestingly enough, some folks turn in some excellent scores with big cheap glasses - Barska, BSA, Tasco (the old Japanese models are held quite dear), Simmons, etc..
I have no heavy rifles. Just don't care for them personally, but I do like to shoot various sporters in their USBR Sporter Class. The USBR Sporter Class does not limit the scope's magnification like some disciplines do. So, I often mount one of my two T-36s on various sporters. I have one at this time on an exceptionally accurate Ruger 77/22 VBZ that barely makes the 8.5 pound USBR Sporter Class weight ceiling.
I have had much success this past year with my ten year old CZ 452 American and it's Weaver Grand Slam 6-20X40. Here is a target we teamed up for last fall that got me off to a good start with a first place in the benchrest stage of our annual Sporter Master Match (a rimfire sporter pentathlon of sorts involving BR, silhouette, 3P, rapidfire, and sniper):
The rifle and scope proved to be a good choice. We took four of the five events and won the day. I won the Sporter Master once before, in the very first year, while shooting the Annie and Weaver V-16 combo as pictured earlier. BTW, that CZ 452 American is stock.