This will be long, but there is some misinformation in this thread.
The barrel taper only matters at the length you want it cut. The Bartlein #3 or Kreiger #4 are almost identical contours, and are correct to thread 5/8-24 at a 22" finished barrel length. If you want 24", you'll need to bump up in contour one number, or go 9/16"-24 threads on the tapers I already mentioned. That is a weight tradeoff of about a pound to go up in contour and thread 5/8"-24 at 24". I would stick to 22" in a lighter contour to keep the rifle weight and balance correct. A suppressor is going to unbalance it anyway, so I would want to keep it more manageable.
Belling on a threaded barrel is rare. It isn't caused by the pressure from firing a cartridge. There isn't enough pressure at the muzzle to deform the barrel. That is a myth that unfortunately still exists.
There are two causes: stress from manufacturing, or the lapped taper wasn't cut off the end. Stress is from hammer forging or button pulling, and they didn't fully stress relieve the barrel at the end. When the muzzle threads are machined, the barrel relaxes to a different size as material is removed. None of this is a concern from good makers like Shilen, Douglas, IBI, Hart, etc. Barrels that are lapped (all cut rifled, and some button) have a short taper at the breech and muzzle induced by the lapping process. It can extend for a couple of inches, but the makers just say to cut off an inch. That cleans it up enough for it to not be an issue.
I have only seen "belling" on factory and cheap barrels (usually unknown make). Even then, they shot fine.
To answer your thread question, 1/2"-28 is the safe minimum on a .308 chrome moly barrel, but you'll need an adapter for suppressor use. On a stainless barrel 9/16"-24 is a safer minimum if the rifle will be shot in very low temperatures (below zero Fahrenheit).
Both manufacturers that you are looking at only make cut rifled barrels. And they make good ones. Flip a coin. If I was your gunsmith, I would tell you to pick the one that has the shorter lead time or is in stock for what you want.
Rifling type is debatable, and IMO, only worth considering if you shoot competition. 5R is supposed to engrave the bullet easier and create a better seal extending barrel life and trapping less fouling. It probably does, if everything else on the barrel is perfect. That said, I would put it at the bottom of the list of concerns, or not on the list at all.
Barrel steel? There isn't a better here unless you want easier maintenance, but coatings negate that to a great degree. Since you want a .308, both will last thousands of rounds.
Prefits are fine if the action is made for it and is square from the factory. Provided the gunsmith is good, you will get a better result with a custom fit barrel so a blank is better, IMO. Prefits are mass produced to fit every action tolerances. A gunsmith can work to near zero tolerance on your action. And they can correct any issues they may find. That said, choose your gunsmith with a lot of research. Not that prefits are bad in any way, but if you are splitting hairs, and in this case, you probably are, a custom fit barrel is slightly better.
Jeremy
