My old Rem. M700 Varmint Special (1 turn 12") really like 45 grain Sierra and Hornady bullets. Very fast, very accurate.
Experiment (if you reload) with different powders. My rifle really liked IMR4198 (but powder charges have to be weighed since it doesn't meter consistently through a powder measure). My AR15 varmint rifle does better with H335 and the 45 grain bullets. Lots of powders will work, you'll just need to figure out which one works best for you.
You may find a factory load that works well in your rifle, or you may find you can make better with a reload of your own. We built a 24" bull barrel AR15 for my nephew and took it to the range to sight in. He doesn't reload. He bought boxes of Remington and Winchester ammo in 50 and 55 grain bullets. We sighted in at 25 yds. and moved to the 100 yd. range. He shot more groups to get his POA/POI where he wanted it for 100 yds.
He shot up his store bought ammo and I gave him some of my standard reloads (55 grain Hornady FMJ sitting on top of IMR4198). When we were done I asked him if he was happy with his groups. He showed my his targets and told me the best groups were with the reloads I gave him to shoot. You may be able to seem me grin from here.
If you don't reload, you won't find out what your rifle can really do.
