Looking at this for the simplest implementation for Barrett, they already produce the following:

Short action (lw contour):
.243 Win - 1 in 7"
.22-250 Rem - 1 in 7"
6.5 Creed - 1 in 8"
6mm Creed - 1 in 7"
7mm-08 Rem - 1 in 8"
.308 Win - 1 in 10"

Long action (~#2 contour):
.25-06 Rem - 1 in 9"
.270 Win - 1 in 10"
.30-06 Sprg - 1 in 10"
6.5x55 Swe - 1 in 8"

I'd think the quickest/easiest would be to go with a barrel they already have and chamber it in something they already cut chambers for. The overlap would be for .308 and 6.5 Creed using a long action barrel (30-06 or 6.5x55). This seems like the no-nonsense option. Very little overhead.

Not sure if they would want to chamber a long action in the lw contour at any length longer than 21" (?)....it wouldn't interest me if they did, but it would fall under the same ease as the above.

Second quickest/easiest would be to use an existing barrel and chamber it in something they don't currently offer. Use any of the barrel/contours/bore/twist rates and chamber it in whatever. Still fairly small overhead to implement.


After that options really open up but I'd guess the cost and effort would increase substantially.