Re: 200gr 7mm wildcat...
Like 257 said, donít waste your time or money trying the 200s in your current barrel. You could probably get them to work under specific conditions and at short ranges, but if the 175s are working then I suggest you stick with them until you re-barrel.
Talk to Kirby when you decide, but if you plan on going with a 7mm and you want to use the 200s Iíd suggest you seriously look at the 7mm AM. Kirby can fill you in on all of the details and what would be needed. My thoughts would be that if you are going to try and launch the big 200s as best you can, and take advantage of the BC and weight at extended ranges then the AM, to my way of thinking, is the way to go. This is not to say that a RUM etc. would not work, itís just that if you are going to go with the best combo for long range shooting, with the 200ís, then I feel the AM and itís case quality and capacity is the way to go. I know you said you donít want to go with an ultra sized case but the 7mm AM, in a properly weighted and braked gun, is a pussy cat to shoot and the result down range is something you have to experience.
One of the things I like best about the AM is the fact that it uses Lapua brass, which some people think is the best brass available. Itís really a piece of cake to prep them for fire forming and the fire forming loads with the 200 grain Wildcats will kill anything you point them at and are great for long range practice. Iíve used the fire form loads this past hunting season out to just shy of 1500 yards and also took a deer and an elk at pretty decent range with them.
You talked about shooting 150-200 grain bullets, but I think you will find, for serious long range shooting, the heavier 200s will do anything you want, and will do it better than a lighter bullet, at long range.
Like I said, talk to Kirby and he can go over with you every case, barrel, cartridge combo there is and then you can make your decision. I do believe, that if you ever get a round that launches the big 200s at top velocities, you wonít ever regret it. Have fun making your decisions and good luck with your upcoming project.