Tech Help With M&P .38 S&W

[jrayborn]

Well I just got a pre-Victory .38 S&W M&P from Gunbroker. It is a just under 1million S/N Austrailian Lend-Lease that was FTR'd in 1954 according to the stamps.

It looks good, shoots well, had a bit of a double action hitch that Mister Kuhnhausen has helped me fix.

So here is my issue. The revolver is in really good shape. It shoots well and is accurate. But it has about .014 cylinder barrel gap. Also about .007 end-shake in the cylinder.

I have shim bearings on the way to adjust the end-shake, but I believe there is nothing to be done about the gap other than to remove the barrel and set it back. I believe I can do this. I am a machinist, I work in a VERY well tooled shop, and am allowed to use any NON CNC machine.

I'm not sure its really worth it though. Realistically the revolver won't be shot a lot. Maybe 5000 rounds if that, and that's probably a very high number. Additionally I am not especially deep pocketed and would need to invest in some tooling to remove and reinstall the barrel and cut the face. But it would put it back into tolerance, and I would be able to learn a lot in the process.

Has anyone here done this type of work? Am I looking for trouble? I absolutely don't want to ruin the revolver. It is a shooter, I am not in it for the "Collector Value". I want it to function. If I do set back the barrel what needs to be done to the ejector rod?

Thanks for any help.

Jon

[MtGun44]

Easy to do if you are a machinist. Measure the threads and skim off about 90% of one
turn's worth from the barrel shoulder. Screw it in and see how you did. If you were on,
go back and take off the remainder. Use red locktight NOT heavy overtorque like S&W does
because they cause a tight spot by overtorquing their barrels. You will then need to have
a hand powered, piloted facing tool to cut the back face of the barrel to reset the clearance.
Brownell's sells the tool to cut the barrel back end, but you can make up a pilot, drive
rod and hand cutter pretty easily yourself if you want to save the money.

Of course, take out the bbl pin first, but understand that there is a wide slot cut in the
threads to clear the pin, so you won't likely have to redrill this or anything. If needed
in the future, heat up the barrel with a propane torche until oil on it just starts to smoke
and the loc-tite will give up. Done it several times, no damage.

The biggest risk is ruining the frame. Make up oak blocks that fit the front of the
frame accurately (easy - make a template, trace onto a pair of 3/4" thick blocks,
and cut out with a router or mill) support the frame front in a vise and unscrew the
barrel with whatever safe wrench you can work up. Shorten the ejector rod
on the front the same as the barrel, no big deal.

Bill

[jrayborn]

That's something I was unsure about, if I had to cut back the rod the .0278 as well or not, thanks!

[MtGun44]

The rod has to be the correct length to lock the cyl, and if too long, the center pin will
not be flush with the end of the ejector rod at the forward end of the stroke, so it
cannot release the cylinder. On the K frame I built from scratch I had to shorten the
front of the ejector until it would release. I was fitting a used bbl to it, not exactly the
same as setting a barrel back, but pretty much the same concept, except your inner
and outer will be the correct length already.

If the travel on the plunger in the barrel shroud is long enough, you may not need to
cut it at all. It is pretty common with a single thread not to need to cut it at all. If it
is too long, cut off as needed. I have watched my friend do a couple of mine that
did not need any cut off, and one that did.

If you want to get rid of the end shake the best and easiest way make or buy a
crane swaging tool.
Grind a ~ .050" flat all the way around on the "cutting" edge of a small pipe cutter
and make a hardened pin that will JUST barely fit inside the crane tube. Then slide
the hard rod into the crane tube and roll a ring into the middle of the crane tube with
the modified pipe cutter. This will stretch the crane tube. Done carefully, it eliminates
end shake, but if you overdo it you will need to dress a touch off of the end of the
crane tube. There is a fancy tool to swage and another to cut the end square, but
the swager is nothing more than what I have described. At least .050 or maybe
even .060 flat to avoid cutting the tube must be ground onto the 'cutter wheel',
and it must be smooth and flat. I have not done this job, but watched my friend
do it multiple times. Here is the tool:

http://www.brownells.com/.aspx/pid=693/Product/CRANE-STRETCHER

The cutter is a piloted spot facing tool with a screwdriver handle.

Bill

[jrayborn]

I have a couple projects on my plate right now, so I think I will try the bearing washers first, and then I believe I might as well start tooling up to set the barrel back. Kuhnhausen shows a pretty clever way to make a barrel wrench using hard wood and fiberglass resin-cloth to exactly mate with the barrel.

I have the forcing cone cutters and gages, just need to get the facing tool and come up with an action wrench. I have made most of mine out of aluminum the same way you describe using hard wood on a mill.

Oh well at least it's winter. It's good to have a hobby!!