Home Forums Hunting & Shooting Gunsmithing Indexing a Fluted Barrel

To index a barrel no matter whether fluted or not, you take one inch (1.000") and divide by the pitch (TPI) of the thread. The answer is the distance from the crest (or root) of one thread to the next. This is how much material you need to remove from the breech of the barrel (and shoulder) to set the barrel back one turn. Divide this by the number of flutes and you get the amount of material to index from one flute to the next. So you see it is easy to calculate moving from one flute (or flat if working with an octagon barrel). I usually allow .001-.002" for crush fit when the barrel is snugged up, it is easy to remove that little bit rather than having to go to the next flute/flat or have to go all the way around another turn. Partial turns from flute to flute can be interpolated (guestimated) once you gain a little experience with the process.