Fixed binding problem on two 50's era N frame Smiths

[Patrick L]

I recently corrected a problem that has been bothering me for 20 years in one gun, just recently in another.

Both my 5 screw pre 25 .45 ACP and my 4 screw pre 29 would bind in DA firing. One shot a cylinder would hang up, and no it wasn't always the same chamber. The .45 would do it 99% of the time, sometimes I could get thru six shots but then always the next 6 would have one stick. The .44 did it once or twice evey cylinder full.

I have had the .45 for just over 20 years now, and I had been told by a "gunsmith " (quotes mine) that the gun was just very tight and that the buildup from my lead bullet handloads was causing the binding. For years I would clean it scrupulously during shooting sessions, even carrying a stainless toothbrush to scrub the cylinder face and breech face between each cylinder full. I had bought this gun to compete in bowling pin shoots, so this was not a good situation. The bowling pin shoots eventually dried up, and I do lots of other shooting activities (I am the definition of jack of all trades, master of none) so the problem was sort of forgotten/lived with for years, as the gun was shot only for fun and usually single action bullseye style. I figured it was just a flukey situation, and I was dumb enough to accept the "expert"'s diagnosis. I really liked the gun, especially since it was a pre model 5 screw, so there was no way I was going to get rid of it. I just lived with it.

Fast forward to last summer and I acquired the pre 29. It displayed the same tendency to bind during DA shooting, but even worse, so I figured there had to be another explanation. The guns were clean, so that was not the problem. I was beginning to fear maybe the indexing parts (hand, star, etc.) might be worn, as both guns are 50+ years old, and repairing them might be pricey.

Then someone on the S&W forum suggested that the guns might have some excessive cylinder endshake (this was after about 50 kind souls who didn't read my post saying that the guns were "scrupulously clean" responded telling me I needed to clean the guns.) I purchase a set of those Power shims and went to work. I did the .44 first, since it was newer to me and I was "hotter" for it. The gun would only take one shim, it wouldn't even close on two. A trip to the range put 50 rounds through it DA, smooth as butter. Success! I didn't get around to tackling the .45 until this week. This one took two shims, but the end result was the same! I realize I am opening up the barrel/cylinder gap a bit here, but given the choice between a tight gap and a gun that works, I'll take the working gun. My theory was that during recoil, the loose cylinders were moving forward as the guns recoiled back, and indeed the buildup of firing residue between the barrel and cylinder face was the problem. The guns could be dry fired until the springs broke and nothing would happen, but add in the recoil of live rounds and things would shift.

Here's the pre 29
http://i204.photobucket.com/albums/bb157/patrickl_01/Pre%2029/Pre29052.jpg

And here's the pre 25, although it now has a set of Eagle repro Cokes
http://i204.photobucket.com/albums/bb157/patrickl_01/Bullets/GunStuff053.jpg

[Bass Ackward]

It's not always end shake. And the fact that two shims (.002 each) in the cylinder and it wouldn't even close, then that means that ES was less than .004. Smiths tolerances are .003 to .009 just for this reason.

But with tight end shake, if the front of the cylinder or forcing cone wore to allow the bullet to exit cleanly and it tipped the front of the cylinder in any particular direction, then the back of the cylinder is going to cant a little. With tight tolerances, this can be just enough to cause what you saw.

This is why Smiths tolerances are what they are. It quit now because you are holding the cylinder back far enough to decrease the transition angle into the cone so it doesn't have to tip. It's also why chamber throats are larger too unless you shoot bigger bullets and remove this advantage.

Don't be surprised that it comes back if you shoot heavier (longer) bullets than you normally use to break it in. (the gun will have to wear MORE to allow this)

So a deeper cone or shorter bullets, bigger throats would have prevented this and you may have to in fact INCREASE end play to get away from it.

[S.R.Custom]

...My theory was that during recoil, the loose cylinders were moving forward as the guns recoiled back, and indeed the buildup of firing residue between the barrel and cylinder face was the problem. The guns could be dry fired until the springs broke and nothing would happen, but add in the recoil of live rounds and things would shift.

Actually, what was happening was just the opposite. (I've seen this before.) These pre-model Smiths typically had very tight barrel/cylinder gaps. Gaps of .002" were common in these old guns. And if your barrel gap is smaller than your endshake --regardless of acceptable tolerance-- you'll have a problem.

When a round goes off, the cylinder moves back, not forward. (Recoil is not the dominant force here.) At ignition, the first thing that happens is the shell case puffs out, for lack of better terminology, and it grips the chamber wall. Because the bullet is resisting mightily as it is being swaged into the barrel, the cylinder is pushed --quite fiercely-- to the rear. Propellant trash is left in the barrel gap as well as under the extractor star with every shot, and as you pull the trigger on successive shots, the hand is pushing forward on the extractor & cylinder. If your endshake exceeds your barrel gap, after you fire off a few rounds, you get the binding you describe.

Endshake comes from a number of places, but the two places to watch carefully are at (1) the rear of the extractor where the center bearing portion meets the frame, and (2) at the yoke/crane....

(1) Over time, the center portion of the extractor --the part that bears on the frame directly-- wears and gets peened a bit, as does the frame itself. Watch this area for wear.

(2) Your crane can be 'walking out' as well. The forward screw that holds your side plate on also keeps the crane from moving forward, by engaging a groove in the part of the crane that goes into the frame. This screw needs to be a tight fit to that groove. If this screw is loose, worn, buggered by amateur gunsmiths, or most commonly, not put back in the proper hole when putting the sideplate back on, this will allow your crane to walk out with the force of recoil, creating instant end shake.

Generally speaking, a lot of endshake problems can be remedied without shims by addressing situation #2. If endshake is a result of condition #1, then shims will probably be needed.

[robroy]

Jerry Kuhnhausen agrees with S. R. Custom

[Multigunner]

I had a Colt Navy replica and a cheap pull pin .38 that both had cylinder drag problems. Both turned out to have cylinder faces that were not entirely perpendicular the the axis of the cylinder pin.

I turned a couple of steel rods to a close fit in the pin hole then wrapped those with thin paper till they were a tight enough fit that I could turn the cylinders in my drill press. I then glued some fine grit silicon carbide paper to a aluminum plate and carefully brought the spining cylinders down face first onto the paper.

While doing this I noticed both cylinder faces had irregular dished areas at each chamber mouth, no more than a thousandth or so deep so not visible when blued. I finished up the chambers and while I was at it I made a new cylinder pin for the cheap .38 and a new barrel latch for the Navy replica. I also set back the barrel of the .38 by one thread. When finished both had a near zero cylinder to barrel gap, and both operated slick as a whistle.

I seem to remember that early model S&W 44 Magnums had a problem with recoil unscrewing the ejector rod causing the end of the ejector rod to drag against the barrel lug until screwed back in place. IIRC they then reversed the threading of that part to cure the problem. I don't own one of those so I can't check to see if thats what actually happened or whether it was just a suggested fix.
If true then a older S&W with the original threading might also unscrew under recoil if the threads are worn.

[Bass Ackward]

The beautiful thing is that the gun will ALWAYS tell you if you look long enough.

If it is hanging up on the barrel, then it will also batter the end of the barrel under recoil as metal moves under pressure or the need to align.

This will, or it has at least on mine, cause a sharp burr to form in very short order. In fact, a custom shop Smith that I actually had to send back, cut me pretty badly. The burr can be either internal or external depending on the location of the contact.

At the very least you will see bright, dull, smooth, rough something metal surrounded by metal not so something someplace. Put on your CSI hat and look.

All you have to do is feel around the inside / outside of the cone or use your finger nail and it will tell you if this is true or not. Then is it end shake or alignment is the next question to ask.