IMHO the best trainer for a bolt gun, is the bolt gun being used. Nothing will replicate that gun, and I think it would be pretty cost ineffective to set up a "trainer" gun in the EXACT configuration. For that kind of money, you can buy a lot of premium .308 ammo. A lot.
Position work, fundamentals, breathing, etc. can all be worked dry fire and be very effective. And unless you are going to relegate your big boy gun to shooting at 200 and in, a rimfire "trainer" isn't going to help you where it really matters at distance. I'm far from the sniper's sniper, but I have occasionally had to make long range shots that mattered. A .22 or .17 isn't helping me understand the in flight ballistics, reading/calling wind, mirage, leads and holds, etc. The only thing that will help me with that, is shooting the gun I intend on using for that purpose.
I'd take that money and buy a couple of cases of premium .308.
If you want a baby bolt gun because you want one, don't let me talk you out of it. But don't fool yourself into believing it is "training" either.