S&w 625

[Pistolero]

Once you start looking for thread choke, you will find a lot of it, unfortunately.
They all shoot better without it. Mine took a bit of fire lapping to do the final
cleanup, it still had perhaps 0.0005 choke right at the forcing cone, permanent
deformation, did not spring back. IME, all the .38 Spl bbls I have done have sprung
all the way back, but they were only about 0.001 to 0.0015" of thread choke. Still enough
to harm the grouping a bit in a Model 14. WCs do not spring back at all. I tend to think
that jacketed may spring back just a touch and help this thread choke be not so noticeable
at the target. Of course, the fact that most cannot shoot better than 4-6" at 25 yds ever, with
any gun makes this issue less of an impact for the majority - they can't tell the difference.

It seems to me that perhaps the EDM barrel process has been or is being abandoned, seems like
fewer guns with it, rather than the same or more. Likely for economic reasons. I have several with
EDM barrels, they are quite smooth looking. I have no particular complaints about them but do
not have a lot of experience with them.

Bill

 

[Ian]

Dogdoc, for what it's worth I used Bill's idea of tapping an aluminum pin in the barrel to good effect on a heavy varmint rifle barrel that wouldn't otherwise fit in my lathe, it worked very well. Chuck up an aluminum rod tightly, turn it to just the slightest fuzz under groove dimension, taper the end to just below bore dimension, insert muzzle onto pin and tap into place with plastic rod while keeping pressure on the live center in the forcing cone with the tailstock quill. Once you get 1/8" of engagement with the grooves you're good to go for taking light cuts, no dog required.

 

[Pistolero]

Not really my idea, got it from a friend. But it does work.

Bill

 

[Ian]

A photo of the muzzle pin I used to turn threads on this barrel:

 

[Pistolero]

In my case, the rod is used over and over again. One for .44 cal, a different one for
.45 cal. once the rifling grooves are broached it will tap into a different barrel
very easily, of course all S&W bbls.

Bill

 

[Dogdoc]

Stupid question for y’all . When you are putting the barrel on the rod, are you removing the rod(or pin) from the chuck and tapping it into place and then reindicating the rod in the chuck with a live center in the tail stock? I am having a hard time understanding how to get the barrel on the pin in a concentric manner . I may try this during the weekend.

Ian, are you just tapping tailstock end of the barrel with a dowel while it is the live center? If so it must take very little effort to broach the brass or aluminum.
Thanks for your patience as I am just a hobbiest with the lathe and mill

 

[Pistolero]

The rod is put in the end of the vertical bbl, bbl rear end resting on a wooden work bench, tapped in
with a small hammer. The pin has a short bore diam section and about 3/4-1" of groove
diam plus another half an inch or so. Just tap it in, about 1/2" of groove diam engagement
is fine.

You are overthinking this whole thing. Not a big deal. Once the muzzle pin is in
place, chuck it up in a collet or accurate three jaw, and put the live center of the tail
stock in the forcing cone. About 2 minutes total setup time if you have the pin already.

Bill

 

[Dogdoc]

Also after in place do reindicate off the barrel shank or other?
Again thanks for the answers

Dogdoc

 

[Pistolero]

No indication at all. Did that long ago when the technique was first
thought up, never bother now. There is no possible way for a solid
rod to be anywhere but exactly in the center of the bore. I don't care
one bit what the outside of the barrel is doing, only the bore.

Bill

 

[Dogdoc]

I am bad about overthinking things. I think I understand now

Thanks

 

[Ian]

I used a disposable scrap of extruded aluminum rod and left it in the chuck so it remained perfectly true for this one-off job I did turn a little surface to indicate off of if necessary or if I ever had to put that same barrel back in the lathe. Keep in mind my muzzle job was for a suppressor where alignment is critical, maybe not so much for revolver barrels. I used the tailstock (actually an inboard spider/cathead in this instance, but you would use the live center/tailstock for a revolver barrel) to keep the barrel centered-up but loose enough to slide as I tapped the muzzle onto the rod in the chuck. Lots of little taps and the crown peels up little curves of aluminum as you can see in the photo.

 

[Pistolero]

As long as the aluminum or brass muzzle pin has a short bore diam pilot,
then a longish groove diameter section, it can go nowhere but exactly into
the center of the barrel. The only possible error is whether the exterior of the
pin, outside of the barrel is concentric to the part inside the barrel, and it should
be made that way. And if you hold that exterior pin in a collet, or an accurate three jaw chuck,
it is centered, and the bore is centered. If you use a four jaw chuck, you will have
to indicate it in, since a four jaw can be anywhere.

The cuts are at the other end of the barrel, on the shoulder, and that end is accurately
centered by the live center on the barrel interior, too.
Pretty much self aligning when you do it this way.

And rest assured that the steel barrel will not be harmed in the slightest by broaching
about 0,004" or 0.005" of aluminum. The aluminum is far softer, can't hurt the steel this
way.

So, to make the pin, cut a 2" length of the aluminum rod to something like .475, and then in the
same setup, leave the left 1" alone, and cut a . 452 section to the right of that for ~3/4", and then a 1/4"
section of about .442" which is 0.001" smaller than my bore diam. (top of the rifling, so it
will be a slip fit pilot) and the .452 is at my groove diam.

Cut off the piece, now you slip in the .442 pilot and drive in the .452 section, which
will be broached lightly by the rifling. The .475 section should be the end of the
muzzle pin, and if you chuck accurately on that, the bore will be centered.

Bill

 

[Dogdoc]

Good info!
Thanks

 

[Pistolero]

One more critical piece of info if you plan on pulling a S&W revolver barrel. You can really
wreck the frame if you don't have a proper frame wrench. Look back at the first photo and you an
see the frame still in an example of a good wrench. If you are handy, you can make one from
with oak or phenolic insert blocks, VERY closely fitted to the frame and crane, and then surrounded
by steel, or you can buy one - not cheap. But way cheaper than ruining a frame.

Bill

 

[Pistolero]

Another tidbit bubble up related to barrel thread choke. I remembered that Ruger had some recall that
was reported to be caused by a corrosion or cracking problem from a barrel thread locking agent. Must not
have been loctite.

Hmmm. S&W torques their bbls so tight that they need no pins nowdays and use no thread locker,
but too many have thread choke.

If Ruger does use thread locker - it indicates to me that they have learned that overtorquing barrels
is a bad thing, which is a good thing for a revolver maker to know, and act on. Perhaps this is why
fewer Rugers seem to have thread choke?

Bill

 

[Ian]

Ruger has been as bad or worse than any of them IME. I picked up either from a Ruger book I have or a factory tour video that some bean-counting engineer type figured out if they just sort barrels and frames into three piles and torque barrels into the frame from the nearest 120 degrees they wouldn't have to face the barrels to fit. So, about 10% of the barrels end up being correctly crushed. My hope now is that CNC lathe technology indexes the thread starts all in the same (and correct!) place.

Threadlocker causing corrosion? Only if they use sodium or potassium silicate...and doubtful at that. I smell a cow pie and am thinking stress fractures from the 300-lb gorilla and 6' cheater pipe at the barrel installation vise.

 

[Pistolero]

Even 45 degrees is too much, IME. Proper bbl torquing is no more than about 5 deg, and use
loctite. I have no Ruger revolvers with thread choke, out of 1 SBH, one .45 BH, a Sec 6, a GP100
and a SP101 .22. Not a huge sample, but a large portion of my S&Ws have thread choke, or
had, mostly.

Bill

 

[RBHarter]

None or not enough to cause any issues in my Sec 6 or BH circa 74&76' the throats were terrible though .