I had to send my S&W 686 and my Colt Python back to the factory recently. For some reason, the rear of the barrels are rubbing against the fronts of the cylinders, to the point that they bind up. I guess the term for that is that the "flash gap" has become too small. My question is if anyone one knows why this is. I've been shooting some heavy .357 loads through them from a company called Armscor, but I don't know if this could have any effect. Thanks for your help.
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My revolvers are jamming
- Thread starter branrot
- Start date
If you have been firing too rapidly, the heating of the cylinder will cause it to expand lengthwise and if the barrel-cylinder gap is too tight, it will drag on the barrel and jam the gun. This has become a problem in cowboy action shooting.
Most people only think that the gap must not be too large; they forget that it also must not be too small.
Jim
Most people only think that the gap must not be too large; they forget that it also must not be too small.
Jim
My opinion is that with frequent cleaning, you can run a tight gap often down around .002". You may need to wipe down the cylinder face and rear of barrel every 40 rounds or so like I do on my .38snubbie, but the payback is in velocity and in something like .38Spl from a 2" barrel, every bit helps (expansion, mostly).
But if your gap really is too tight for your gun, or your ammo, fine - take a fine knife sharpening stone and VERY gently polish (BY HAND ONLY) the rear of the barrel. Go dead slow, and frequently check the gap. If you send it back to the factory, God only knows what you'll get back - .007" is the traditional industry standard max, and S&W has been telling people that gaps up to .009" or so are still "in spec" :barf:. Do it yourself, and you can set it for .002" to .004" as you like - I wouldn't go bigger than .004", myself.
Instructions for checking the gap while the gun is in "full lockup":
http://www.thefiringline.com/forums/showthread.php?s=&threadid=57816
But if your gap really is too tight for your gun, or your ammo, fine - take a fine knife sharpening stone and VERY gently polish (BY HAND ONLY) the rear of the barrel. Go dead slow, and frequently check the gap. If you send it back to the factory, God only knows what you'll get back - .007" is the traditional industry standard max, and S&W has been telling people that gaps up to .009" or so are still "in spec" :barf:. Do it yourself, and you can set it for .002" to .004" as you like - I wouldn't go bigger than .004", myself.
Instructions for checking the gap while the gun is in "full lockup":
http://www.thefiringline.com/forums/showthread.php?s=&threadid=57816
A common cause of this (I found out the hard way) is failing to carefully clean inside the cylinder where the crane tube goes in and then lubing the end of the crane tube with a good grease like Tetra Gun grease (requires removing the crane and cylinder). the end of the crane tube is a high stress point. If it wears away, the cylinder moves forward toward the barrel. Check for end shake in the cylinder (front to rear play) If it is .002" or more, you can have washer put in to take out the shake and move it .002" back from the barrel.
Dfariswheel
New member
I think the key words here are: "I've been shooting some heavy .357 loads through them".
A steady diet of heavy loads will cause the revolver to develope excessive cylinder end shake.
A properly adjusted revolver should have almost imperceptable fore-and-aft movement of the cylinder in the frame.
Heavy loads or heavy use will batter the frame/cylinder crane and allow the cylinder to actually "slam" back and forth. The more it's shot, the more it can move, and the more it can move, the more it batters itself.
Eventually the gun is worn so much the cylinder can actually begin to contact the rear of the barrel. At this point, the cylinder will begin to display barrel battering marks on it's face, and the rear of the frame will show ejector battering.
Colt Pythons are usually noted for having very minumim cylinder end shake. Guns displaying shake have usually been shot with over powered loads.
If you want the gun to last, back off the heavy loads. Unless there's a specific reason for shooting over power loads, stick to standard Magnum, preferably American ammo.
A steady diet of heavy loads will cause the revolver to develope excessive cylinder end shake.
A properly adjusted revolver should have almost imperceptable fore-and-aft movement of the cylinder in the frame.
Heavy loads or heavy use will batter the frame/cylinder crane and allow the cylinder to actually "slam" back and forth. The more it's shot, the more it can move, and the more it can move, the more it batters itself.
Eventually the gun is worn so much the cylinder can actually begin to contact the rear of the barrel. At this point, the cylinder will begin to display barrel battering marks on it's face, and the rear of the frame will show ejector battering.
Colt Pythons are usually noted for having very minumim cylinder end shake. Guns displaying shake have usually been shot with over powered loads.
If you want the gun to last, back off the heavy loads. Unless there's a specific reason for shooting over power loads, stick to standard Magnum, preferably American ammo.
All the comments about endshake are true, but that results in a loose cylinder, not one that binds. Jim, IMHO, .002 is too tight for a gun in ordinary use. For a snubby that will be shot only a few times and cleaned regularly as yours is, it might be OK, but it still is tighter than it needs to be. The velocity loss with, say, a gap of .004-006 is not, IMO, great enough to take a chance of the gun not working at all.
Jim
Jim
Smith & Wesson specs are from .004 to .006 B/C gap. The guages that come from S&W are .004 and .007. If the .004 does not fit, adjust it. If the .007 end fits, it is barrel set back time.
I agree that endshake does not play in cylinder lock up on the barrel, unless somehow a bunch of crud worked into the back of the yoke. Highly unlikely though.
BTW, Washers can be used on the Colt, but that is not S&W armorer spec for the S&W.
When barreling, or setting back a S&W revolver, I always give a .004 B/C gap. The cylinder has to have minumum run out though for this to work when when the gun is very dirty.
FWIW
Celt
I agree that endshake does not play in cylinder lock up on the barrel, unless somehow a bunch of crud worked into the back of the yoke. Highly unlikely though.
BTW, Washers can be used on the Colt, but that is not S&W armorer spec for the S&W.
When barreling, or setting back a S&W revolver, I always give a .004 B/C gap. The cylinder has to have minumum run out though for this to work when when the gun is very dirty.
FWIW
Celt
part swede
New member
The symptom with my 686 was the same as above, the problem was excessive endshake, and the solution was an endshake washer (have to buy them in packs of 10 from Brownells). Did it myself.
"Washers can be used on the Colt, but that is not S&W armorer spec for the S&W."
True. The official S+W "fix" for end shake is to peen the end of the yoke tube against a precision insert rod to lengthen it, then regrind the end of the tube for zero cylinder end shake. I think the washers are a good fix as well, and have an advantage:
The washers are actually harder and smoother than the SS the cylinder and crane are made from. Putting in a washer stopped the wear on the crane/cylinder interface that made it loosen up in the first place (I shoot only .38 standard loads).
I also installed the washers myself after lightly polishing the inner surface of the cylinder where the tube rides. That gets a ridged groove in it after a lot of firing which will keep the washers from laying down flat.
True. The official S+W "fix" for end shake is to peen the end of the yoke tube against a precision insert rod to lengthen it, then regrind the end of the tube for zero cylinder end shake. I think the washers are a good fix as well, and have an advantage:
The washers are actually harder and smoother than the SS the cylinder and crane are made from. Putting in a washer stopped the wear on the crane/cylinder interface that made it loosen up in the first place (I shoot only .38 standard loads).
I also installed the washers myself after lightly polishing the inner surface of the cylinder where the tube rides. That gets a ridged groove in it after a lot of firing which will keep the washers from laying down flat.
I'll have to try the washers sometime when I do another S&W. I have not done any for awhile, but did work S&W warranty for a number of years. They would be ticked off if it was not done to their specs.
Sounds like they would be the ticket though. It would save the crane too. You can only fix endshake so many time the S&W way.
Celt
Sounds like they would be the ticket though. It would save the crane too. You can only fix endshake so many time the S&W way.
Celt