leftiye
10-02-2008, 03:09 PM
Hi, I mentioned this project way back, and have been fiddling with it a little at a time ever since. It is a Model 10 (fixed sights) mated with an H&R 32 mag. 8 3/8" barrel with full under rib and cylinder for same caliber which I got from Numrich arms, plus a Millet rear adjustable sight.
Modifying it for the rear sight was the hardest part. You not only have to mill a groove down the top of the top strap, but you have to mill a T- slot at the rear for the S&W elevation t-slot nut. This t-slot is only about.040" thick and a special cutter had to be made from an endmill of appropriate diameter. Daunting at first, but once done, not so bad. The frame material on the Model 10 was free cutting (this was also a scary part, if you mess this up you start over with a new revolter), smooth cutting, and easy to mill.
Setting the barrel back to get a tight cylinder gap was somewhat tricky as the calculated cuts didn't produce the desired gap dimension, probly because of the cut suface "wearing in" when the barrel was installed. Took two tries because of this, and you have to make sucessive .001" or so cuts to bring the shoulder to where the barrel lines up (sights, and top flat) properly when tightened. I would because of this wait to cut off the barrel shank until after getting the shoulder right, and then follow the same procedure of small cuts to get the shank out of the way of the cylinder when it closes, and then obtain the desired cylinder/barrel gap (probly no extra cuts needed at this point if you want a small cylinder gap. A 5 degree forcing cone reamer was bought from Dave Manson and applied to the rear of the barrel after all else was completed.
As far as sheer work goes, fitting the cylinder would best be described as a nightmare. S&W factory cylinders have a LOT of extra metal on the rotating star, not so much on the rear, but on the lugs of the star where they bear against the hand when rotating. The correct surface to abrade must be identified (or you will ruin your extractor) and these filed, and finished with a diamond lap (not lapping compound, the abrasive hand tools), and just plain operating wear for the final fit. If you do it right, the result is no movement side to side is possible when the cylinder is locked up at the firing position. Chambers were lengthened slightly with a .339" reamer (factory chambers were over .100" too long for .32 H&R mag) to allow chambering the .327 mag. ctg. Chamber mouths were opened to .315" to match the barrel's .314" groove diameter. The headspace was brought down below minimum specs. ( case rims are still as much as .010" below minimum spec.), BEFORE fitting the barrel. Two .002" shims were installed to take out all feelable end play in the cylinder (also done before fitting the barrel - you should be able to see why). A .005" cylinder gap was obtained. I at first wanted a .002" gap, but decided it was too tight.
Of course a trigger job, and some touch up with Brownell's Oxpho Blue (I want to thank you guys for turning me on to this. It is the only cold blue I've ever seen to do a creditable job.) and now I'm having to keep it at arm's length to keep from slobbering all over it. I'm computer challenged, but I'll try to get my sexytary (wife) to help me get some pictures shortly. Now I have to get a reamer modified to open my 311316 Lyman mold to cast .315" diameter, as the barrel must have been a second as it has .314" groove diameter.
Modifying it for the rear sight was the hardest part. You not only have to mill a groove down the top of the top strap, but you have to mill a T- slot at the rear for the S&W elevation t-slot nut. This t-slot is only about.040" thick and a special cutter had to be made from an endmill of appropriate diameter. Daunting at first, but once done, not so bad. The frame material on the Model 10 was free cutting (this was also a scary part, if you mess this up you start over with a new revolter), smooth cutting, and easy to mill.
Setting the barrel back to get a tight cylinder gap was somewhat tricky as the calculated cuts didn't produce the desired gap dimension, probly because of the cut suface "wearing in" when the barrel was installed. Took two tries because of this, and you have to make sucessive .001" or so cuts to bring the shoulder to where the barrel lines up (sights, and top flat) properly when tightened. I would because of this wait to cut off the barrel shank until after getting the shoulder right, and then follow the same procedure of small cuts to get the shank out of the way of the cylinder when it closes, and then obtain the desired cylinder/barrel gap (probly no extra cuts needed at this point if you want a small cylinder gap. A 5 degree forcing cone reamer was bought from Dave Manson and applied to the rear of the barrel after all else was completed.
As far as sheer work goes, fitting the cylinder would best be described as a nightmare. S&W factory cylinders have a LOT of extra metal on the rotating star, not so much on the rear, but on the lugs of the star where they bear against the hand when rotating. The correct surface to abrade must be identified (or you will ruin your extractor) and these filed, and finished with a diamond lap (not lapping compound, the abrasive hand tools), and just plain operating wear for the final fit. If you do it right, the result is no movement side to side is possible when the cylinder is locked up at the firing position. Chambers were lengthened slightly with a .339" reamer (factory chambers were over .100" too long for .32 H&R mag) to allow chambering the .327 mag. ctg. Chamber mouths were opened to .315" to match the barrel's .314" groove diameter. The headspace was brought down below minimum specs. ( case rims are still as much as .010" below minimum spec.), BEFORE fitting the barrel. Two .002" shims were installed to take out all feelable end play in the cylinder (also done before fitting the barrel - you should be able to see why). A .005" cylinder gap was obtained. I at first wanted a .002" gap, but decided it was too tight.
Of course a trigger job, and some touch up with Brownell's Oxpho Blue (I want to thank you guys for turning me on to this. It is the only cold blue I've ever seen to do a creditable job.) and now I'm having to keep it at arm's length to keep from slobbering all over it. I'm computer challenged, but I'll try to get my sexytary (wife) to help me get some pictures shortly. Now I have to get a reamer modified to open my 311316 Lyman mold to cast .315" diameter, as the barrel must have been a second as it has .314" groove diameter.