Barrel life
Familiarize yourself with the Heat Index of various powders. The Heat Index is related to how hot a powder burns, not to be confused with how much powder you burn. The Heat Index chart is not the Burn Rate chart that is so popular.
AA2700
H1000
N160
N165
Are all very cool burning powders.
Also related to barrel life is the amount of freebore you start your new chamber off with. With factory 257 Weatherby's(.300 freebore), I have seen the very best barrel life in the first 600 rounds with 800 being a stretch. If you take that same 257 Weatherby, reduce the freebore from .300 to .030, and you have at least doubled the very accurate barrel life.
It is shocking to see the difference in a barrel that has shot two different powders, H4350 and N160...SHOCKING is an understatement.
Current thinking is to design a reamer where the bullets boattail/bullet shank, intersects the neck/shoulder junction on the case. By following this design, you eliminate the need to monitor brass for doughnuts, as most do not want to be bothered with doughnuts. Also, the above design aids "bullet release".
In most of my cases, I stuff the bullet down in the case further in shorter freebore chambers. I do monitor for doughnuts, with Accuracy being 3/8" and less.
Reamers are quite an investment for a gunsmith. Gunsmiths need reamers to satisfy a variety of customers' needs. The most advanced gunsmiths will be successful enough to have multiple reamers per their most popular calibers. Some of the most advanced gunsmiths will order very short freebore reamers and throat to the customer's needs, where there is a small charge for the time to "custom throat". Gunsmiths of this mindset are a rare breed, and are worth your effort in seeking out.
Douglas barrels has over 2000 reamers on hand, and Pac Nor is not far behind. I have had great service from Stan Taylor at Douglas, who is one heck of a barrel smith. Pac Nor has some advanced machining as well with short freebore chambers and the ability to "custom throat" per the customers' rounds.
In my 220 Swift, 22/250 AI, 243 Win AI, 6 Rem AI, the choice is AA2700 for long barrel life, hard to imagine just how fast I shot out barrels using super hot burning Varget, IMR 4064, and H4895. R#17 starts fire cracking the barrel in 400 rounds in some calibers, and I use this powder for specialty hunting loads, ONLY.