I had a Wichita Mk 40 in 7mm IHMSA. It had all the needed features for silhouette shooting. The left bolt, left port allowed you to never change your grip during a string. The rear sight had a four position detented adjustment (each detent was adjustable) for the chickens, pigs, turkeys and rams. The windage was on the front sight, and was seldom used. I won the 1986 IHMSA Missouri State Unlimited championship with that gun (then I retired).
The left bolt, left port is preferable, but not necessary, it just saves all that fumbling around when reloading. When you say you want to "build a small centerfire pistol" do you mean small in size, or small in caliber?
The 7 IHMSA was great for knocking down those 70 pound rams, I used a 160 gr bullet, but if I built one today, and wasn't shooting rams, I would probably go for a 6 BR with a no turn neck. Just buy brass and load it, no screwing around with a wildcat caliber. Larger calibers and really hot loads are no fun with a pistol, being able to hit small targets at 200 to 300 yards IS fun.
pic from Wichita's website.
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