SS,
Unless you have access to a large supply of fresh 225 brass I would recommend staying away from that case. It seems to be drying up, just give old J.D. Jones a call as ask him about 225 brass for his wildcat rounds.
I would have to say that the BR hulls would be about the best powder volume for the .204" calibers in a 17" barrel. Anything much larger and you'll just be dealing with increased muzzle flash and blast.
As said before, the Improved version of this case would also be a consideration since your going wildcat anyway, why not improve it.
Even with fireforming cases, this case volume will not shorten throat life a great deal if done so properly.
I personally feel the 50 gr .204" bullets are the best of the bunch, this caliber actually makes alot of sense to me with these bullets.
I will say that putting any sub bore in a 17" barrel will limit velocity potential but who am I to talk, I love my new 6.5 WSM XP-100 with its 15" barrel.
Developed one load to get me through this season with the 120 gr Ballistic Tip loaded to 3150 fps. I will only be using it on deer so this bullet will perform very well.
I have shot +30 groups with it to date and the largest at 100 yards was .881" and it has shot over a dozen groups that were in the 3's ctc.
I am very happy with this round so far.
After the big game rifle rush has passed over the shop I will start playing with this handgun at extreme range as it has a 1-8" Lilja barrel on it for the VLD and ULD rounds.
Good Luck with your XP project, let us know how she runs!!
I do not know it I said this before so congrats on your goat, fine job!!!
Good Shooting!!!
Kirby Allen(50)