semi-auto: ruger 10/22. you should already have two or three of those anyhow
, but if you don't, pick one up and have the barrel threaded. good, reliable gun, with lots of options for parts out there.
bolt-action: don't really know. my one and only bolt-action firearm is a CZ452 American. it came with a 20" barrel that i had cut and threaded to 16.25" and 1/2X28. i didn't wan't the one that comes threaded because, even though it's called the "American" it's threaded euro, so you'd need an adaptor made to use your suppressor on it. nice gun overall, but i'm not completely happy with it. it was a bitch to find rings that fit the rail (cz says 11mm for all their guns... EXCEPT the american which is 3/8. only it's not 3/8's since they measure their bases differently, so it's actually 13mm.
unfortunately, the only set i could find wasn't high enough for my bolt handle to clear my optics...), and i've had to file my mag down for it to fit the gun it came with. otherwise, you couldn't remove it once inserted... also, you'll never be able to find extra mags for it.
look into a ruger 77/22. they can be had in a ton of configurations, they are much easier to mount optics on, spare parts are easy to find, and [i beileve] mags are common with the 10/22.