N.O.S Barrel on a used revolver?

[Jersey Doug]

Brand new unused S&W barrels from the 70's are they made oversize so as to get the proper cylinder/barrel gap the barrel has to be cut to fit? Assuming it has to be cut, is it done by Lathe, milling machine, or surface grinder.
Sure this has been asked and answered many times , but I'm new here, thanks.

 

[Goblin]

Welcome to the forum!

Yes, they're oversized. The tool is similar to a cleaning rod. A guide slides into the barrel to keep the rod centered and a cutter is then threaded on and used to cut the barrel face until the gap is right. Then a different cutter is used to cut the forcing cone.

 

[Jersey Doug]

Thanks for the info, the cylinder sticks 1/3 across the barrel when closing, looking at removing around .005-.006 would think?

 

[ron_c]

Welcome to the forum!

Yes, they're oversized. The tool is similar to a cleaning rod. A guide slides into the barrel to keep the rod centered and a cutter is then threaded on and used to cut the barrel face until the gap is right. Then a different cutter is used to cut the forcing cone.

Brownells made these tools at one time, not sure if they still do.

 

[Protocall_Design]

That is the correct set for .38 - .45 cal. They also have a similar set for .22 - .32 cal. Still sold at Brownell's.

 

[minconrevo]

Very careful use of the Brownell tools is essential. It's easy to cut too much off or to over cut the forcing cone.

Cylinder has to be dead level, with the crane not bent or anything else.

 

[Protocall_Design]

Yes, it is best to set the headspace and endshake first.

 

[dfariswheel]

There's a LOT more to it than that.
A factory new barrel is oversized in several areas.

The first step of fitting a new barrel is to use a lathe or a bench top cutter tool to trim the barrel shoulder so that when the barrel is properly torqued onto the frame, the front sight is at exactly 12:00 O'clock top-dead-center.

To remove the old barrel and torque the new barrel in place a barrel vise insert to hold the barrel and a special frame wrench with the correct polymer inserts to fit that specific brand and size of frame is needed.
The old trick of using a hammer handle through the frame is how frames are bent or cracked through the bottom of the barrel thread area.

Once the barrel is in place a cutter tool that works down the barrel is used to trim the face of the barrel to set the proper barrel-cylinder gap.
This can also be done by using a lathe, but the barrel has to be removed and re-installed at least once.

After the gap is set the same tool set is used with a special cutting head to cut the forcing cone at the rear of the barrel.
There are several angles of cutter that can be used depending on what type of bullets you'll use and other factors.
In order to do this a special drop-in plug gage is used to gage the forcing cone to insure the size of the forcing cone is correct.
The critical dimension is the outer mouth of the forcing cone, not the angle or depth.

After the cone is correctly cut another brass lapping head and fine valve grinding compound is used to lap the cone smooth.

A lot of people who attempt to do their own barrel change are astounded when they screw the new barrel on and the front sight is no where even close to aligning.
They just expect that a barrel will screw on straight and it's off to the range to shoot it.

Even many of today's gunsmiths have no idea the forcing cone is more then just some sort of funnel in the rear of the barrel.
Some of them don't even notice there IS a forcing cone or know how critical it is or that it has to actually be gaged.

The worst are the one's who read in some old gun book or magazine about jamming the barrel in a vise with wood blocks and using a hammer handle or shaped 2x2 to twist the frame off.
They often wonder what that odd "PING" sound was as the frame cracked, or wonder why the gun doesn't shoot right or the chambers line up correctly on the bent frame.

 

[ron_c]

"After the gap is set the same tool set is used with a special cutting head to cut the forcing cone at the rear of the barrel.
There are several angles of cutter that can be used depending on what type of bullets you'll use and other factors.
In order to do this a special drop-in plug gage is used to gage the forcing cone to insure the size of the forcing cone is correct The critical dimension is the outer mouth of the forcing cone, not the angle or depth."


When using these gauges and trying them on some S&W revolver factory barrels, especially the .44 Special and .44 Magnum, the gauge would drop quite a ways down in the barrel as S&W used a large forcing cone. Not sure if all .44 models were this way. Also, these would not work on Dan Wesson barrels as the part of the gauge that fits into the bore were too large. Dan Wesson barrels also had a .0005 choke on the muzzle end of their barrels.

 

[Jersey Doug]

Thanks again for the excellent info. I really was hoping barrels were like engine bearing where you have standard ( install and you're all set) or check the application and buy .001 or .002 oversize type, darn!! Before here, through instinct made starboard impression blocks and used four c-clamps on those frame blocks turned the frame off without flex. I changed my M-28s barrel to a M-27s 8 3/8 with the barrel luckily tightening ending up just where it should.Then Leupold scoped it. Did have a stuck barrel pin gave me grief. Beyond that, I'm doing research before deciding about this complexity of new barrels. For my pristine revolvers (need to long barrel and scope because of eye sight) I will need to find a component gunsmith agreed.
On my every day shooters,, while working in a machine shop modifications I attempted (guided by issues of Shooting Times Magazine this being the mid 70s) worked out well so haven't been burned yet or backed into a corner. To learn, have recently brought an empty K-frame to see how much trouble I can get myself into building it as a learning project. There's a lot of great info available so not so much trail & error as the past.
I'm sure there's plenty of dumping off on-line of defective, worn, and damaged gun parts, you can get stung (it's what they DON"T tell you is found out later) ,, although have found some of the most straight dealers ever there too. I mainly pay the 25% extra (instead of "good condition?") for N.O.S.whenever possible.