Sorry about the curve ball, it was referenced with an IR 50 target in mind. That's my frame of reference regarding .22's

I believe the faster twists in the centerfire are for heavier bullets. You need the faster rate to stabilize them at our velocities.

40-82Hepburn - I don't have any way to post them but if you will PM me your snail mail address I will make copies of both Eley and Lilja chambering reamer specs and mail them to you - you have a good day now - the rimfire - cdpersons

Rimfire, I believe you may have misinterpreted something. Bill, Chet and others do in fact believe the throat has to be lapped in, or burnished, as Bill calls it, but it has less to do with sensitivity than consistancy.
 Among the advocates of it, it is believed that it helps the base upset properly and seal well, it helps reduce the buildup of accuracy robbing lead-carbon ring building in the leade, as well as aiding that initial wax distribution.
 It is my personal belief that the reduction of that ring of fouling might be the most critical.
 Lots of the non-cleaners don't realize that once that hard ring builds, every slug that passes through it gets swaged down and will not seal as well, robbing accuracy in so many good barrels. We are only talking, maybe, a couple tenths but remember we have come to understand in rimfire match barrels, a bit of taper in the bore is desirable, but if you swage that slug past that hard ring of fouling, guess what, you have no more taper.