Have a 28" shilen barrel that I got from Midway originally billed as a 26" barrel. I understand the barrel is lapped and this alters the diameter/quality of the muzzle so that it needs to be shortened. The question is do I have to trim back to 26" or can I leave it longer?

Thanks for your help!

I usually go a inch off one end and chamber the other for a 27" barrel. You might get by with a 1/2" but I'd do 1" to be sure.

grkldoc, trim both ends, the chamber reamer needs to start in a true bore also.

Trim both ends. I usually take off an inch at the muzzel and face the breach deep enough to remove the 60 degree center cone. I then cut new 60 degree centers on both ends. I usually end up at about 26 inches.-Rob

Rob,

When you cut new 60 degree centers what do you use? What diameter bit do you use?

I've seen piloted center drills for sale but wondered if they were really required?

Thanks,

Mike

Thanks Wally!

One last related question: Do these have interchangable pilots or are they caliber specific?

Many Thanks,

-M

The easiest method is to use a piloted center drill. JGS for example sells them in different sizes depending on the caliber you are using. You don't really need one unless your in a hurry, as you can easily cut a true 60 center with your compound assuming you have a spider on your lathe headstock.
All pilots are not the same. If you go the piloted center drill route, You should buy a set of pilots and should choose one that just fits the barrel lands with minimal clearance. Then use this pilot on your reamer when chambering Hope this helps.-Rob

If you rough out the chamber end with a drill smaller than the reamer diameter(so as to decrease the burden on the reamer)doesn't this make trimming the chamber end a mute point? That is rough the chamber deep enough to allow the pilot to enter the bore before the shoulder of the reamer starts to cut. It seems the pilot would then be keying off the bore 1-1.5 inches down the barrel.

The chamber end needs a perfect 60 degree center as does the muzzel end in order for you to turn the shank of the barrel concentric to the bore, assuming you are going to turn your barrel between centers. If you are going to turn the barrel shank in the headstock you will need to dial the barrel in using indicator rods on both ends and a spider to hold the barrel properly centered. The chamber end of the barrel is also often not be square with the bore, so it needs to be faced. Since most of these barrels come with some type of 60 degree center and you have no way to know how it was cut or what shape the tooling was in, you are much better off cutting your own center.
As for using a drill to remove metal to make it easier for the reamer,you can do so, but your chances of producing a concentric chamber are much increased if you simply use a properly piloted reamer in a barrel running true in a center rest. I don't use even a piloted drill except for .50 BMG and larger situations where ALOT of metal must first be removed. -Rob