American Handgunner May/June 1978

or six inch factory tube that you're goin totake off anyway can be a meaninglesswaste of time. I'll just remove the cylinderassembly, take the barrel, pin out, and unscrewthe original barrel. You should,however, have headspace and cylinderalignment taken care of beforehand.When you're putting a barrel on or takingif off, whether it's a Smith or a Douglas,you should always use a specialwrench. I made mine myself, and I haveone each for "K" and "N" frames. Theyfit exactly the contour of the front of theframe. You're putting a lot of stress onthat frame when you clamp the barrel in avise and start unscrewing it, and if youdon't have a wrench that perfectly fits andprotects the frame, there's good chancethat you'll spread the frame, or spring it.You should also have special barrelblocks in the vise, wooden blocks cut to fitthe shape of the barrel: one for the Douglas,and one for the factory barrel. Don'tuse any more muscle than you have to.Once the factory barrel "breaks" loose, itusually unscrews easily.Headspacing and basic "Convertability" of the gun should be accomplishedbefore barrel work is done; cylinder tightening will take place later.A .38 round, with number etched. on side of bullet, is inserted inchamber stamped with same number.One check for cylinder alignment.Starting with the Douglas Premium barrel,if the gun is going to have a six-inchbarrel, I'll cut the blank to a little over6". You should always figure on the barrelbeing bad right at the point where theystart to cut the rifling, so plan on cutting ahalf to three quarters of an inch of barreloff each end and throwing those piecesaway.The reason is that you have to allowfor the time it took the rifling machine toget straightened out and startcutting per-. , . A 8fectly true* :;, :. , ': ..-$' * ,POWER ON A $' ,,ACUTTING THREADS *Before- you start cutting, measure thelength of the barrel extension, while thebarrel is still out of the frame. I take thismeasurement from the front of the frameto the front of the cylinder with a depthmike. This usually runs about .800" or alittle more, though some guns go as muchas .809" (for .38 Special). Figure .006"for the barrel cylinder gap. Some peoplelike a tighter gap, like .003" or .004", but1 think that's a little too snug in case youhave to go 250 rounds in a match withoutcleaning. Lead will accumulate, and yourcylinder may start to hang up. I can accept.005 or .007, but anything approaching.008 or more is going to cause a lot of spitting..006 is the ideal to go for.Get the diameter of the shank for eachindividual frame. Most K frames runaround .547 average. .Some may be aslarge as .550, or as small as -540. In orderto get a perfect fit on threads, the shankdiameter should be same diameter as thatof the barrel hole in the frame. 'So, when you're measuring the barrelextension, figure on that .006" gap andtreat it as .007" because you're going tohave a little "crush" there as you tighten itup later. You'll gain a thousandth of an. - '.inch as you torque in the barrel.-,Measure the length of the threads from'" :the shoulder of the barrel. The threadlength will be about .615" on the shank.The diameter of barrel extension protrud-ing through frame is .512j1. This is a little ".bigger than factory, and gives more '? 'strength in the forcing cone. I cut my I"threads on a lathe, one at a time, 36 "El" ,threads to an inch, and I'll clean them out ¥ .'and finish fitting them with a small three- ,-corner file.Since the front end of the S&W frameis not 100% supported, it's a good idea tocut a little relief on the shoulder of thebarrel where it will meet the frame. Therelief should be even, and between .002"and .003".The barrel also needs to be throated atthe forcing cone area. I use a specialthroating reamer that I run about '/id'deep, with plenty of oil on it and runningthe lathe at slow speed for a nice smoothcut Then I put a 30 chamfer on the backedge for the forcing cone. I'll then polishout the barrel, usually with a Dremel tooland soft abrasive rubber tip. This givesyou a slick, mirror-like finish that's lesslikely to lead up on you.During the fitting, put the barrel intothe frame just snug. You don't want it tobe more than hand-tight With the frameout of the barrel, you can observe that atone point, the frame surrounding the bar-ICAN HANDGUNNER * ~IAYIJUNE 1978