Jimm,
I really recommend limiting barrel length to 30" unless you have a dedicated Heavy rifle in mind. The reason is that past 30" of barrel length, barrel mass really becomes critical in maintaining proper barrel rigidity for extreme accuracy.
In the 338 bore size, 2" of added barrel are really not that advantagous to velocity gains. You will see around 35 fps gained with the Lapua Imp and around 45 fps gained with the Kahn from 30" to 32" of barrel length.
The reason is because the 338 bore is relatively efficent even with these case capacities.
If someone wants a heavy rifle then I say go with at least a 34" barrel or even a 36" pipe but for a medium weight rifle I like to recommend a 30" barrel length and a #7 contour at very minimum for a 300 gr ULD bullet at these velocities.
Actually prefer a #8 contour to be honest but a #7 will work if weight is a concern.
For a heavy rifle, the use of a V-Block system greatly stabilizes the barrel, even if it is a 40" barrel. For a V-Block I like to use a V-Block that is at least 30% the length of the barrel.
For example, if you use a 36" barrel, 30% of that length would be 10.8". I would use an 11" V-Block.
Using this length of V-Block, you would only have 25" of unsupported barrel which translates into a VERY STIFF BARREL!!
It just depends on the type of rifle you are looking to have built and what you want to use it for as far as barrel length is concerned.
Kirby Allen(50)
