patrickcudd, are you talking a pistol barrel or a rifle barrel? I had a 416 Rigby rifle barrel made by T/C. It was actually fun to shoot, the muzzle tamer worked great, I took a 1800 lb Asian water buffalo with one shot from a 300 gr. Barnes X bullet at 135 yards.
If you are talking a pistol barrel length 416 Rigby, I know T/C did not make them that length. It was either cut back and re-crowned by someone's local gun smith, or sent to a custom barrel maker.
The 416 Rigby Rifle barrels did not come with iron sight, they are made for a scope set up, but that should not stop you from having a gunsmith put on iron sights as it can be done.
I had a T/C 480 Ruger pistol barrel that I had cut down to 8 inches, and then re-chambered to 475 Linebaugh. I also had them install a muzzle brake, and re-drill the barrel for a front sight, so I can use it with a scope or use the iron sights. The work was done by Gary Reeder at Reeder Custom Guns.
I have a 375 H&H barrel I had cut down and a brake added. It is 16 1/4 inches long and I shoot it a pistol set up. The 375 H&H can also be set up as a carbine.
As for when you should have more than one frame, that is up to you, I have 4 Encore frames and 7 Encore pistol barrels. I would actually like to have a frame for each barrel.