Ratchet teeth gouging blast shield when closing cylinder

[Hapworth]

Noticing a touch of binding on an L-frame when closing the cylinder.

Found a slight gouge in the blast shield where the ratchet teeth usually clear closing the cylinder. Now they barely pass without touching if I hold the cylinder forward when returning to battery; without doing that, they catch the shield.

Didn't used to do this. Was recently in for the "M" stamp, and the factory fixed a touch of endshake gratis. Set it to less than .001", nearer to zero.

Any chance these are related; if not, any suggestions?

 

[armorer951]

Could be related to the reduction of the end shake by S&W. The gauge between the rear of the cylinder face and the breechface when the cylinder is closed is supposed to be .060" - .064". It shouldn't be "binding" when it is being closed. There needs to be some "end shake" (gauge) in there, between the end of the yoke tube and the bearing surface inside the cylinder, for the gun to function normally, that is, for the cylinder to open close, freely rotate, etc. It seems as though closing end shake to the bare minimum has taken on "compulsive" status.

If there is no debris under the extractor, the gauges are correct, and the cylinder rotation seems normal after the cylinder is fully closed, this incidental contact may disappear after the gun is fired/used a bit and the rear gauge opens back up.

Could also be some wear on the frame lug, which is designed to hold the cylinder in the optimum position during opening/closing....and prevent the cyl from moving rearward when it is in the "open" position. Usually, holding the gun in the "muzzle down" position will prevent the contact you are describing, which, BTW, is also minimized when the gun is loaded rather than being closed when empty.

Wear on the end of the center pin can also have a minimal effect here, but it usually takes years, and a lot of opening and closing cycles.

 

[andyo5]

Make sure that the extractor rod is not loose. It has reverse threads.

 

[chief38]

Hap,

There are basically two ways of reducing or virtually eliminating end-shake. First is with Shims and the other is by stretching the barrel of the Yoke. IF the Factory used the Shims, you can possibly remove one. They are usually installed in .002' AND / OR .004" thicknesses. Removing one of the .002" shims might help. IF they stretched it then removing .001" to .0015 with a Hard Arkansas Stone would probably also help. I know the Factory used to use a devise similar to a copper pipe cutter to "stretch" the metal, but I am not sure how they do that now.

I would disassembly the cylinder/ER assembly and see what goes. I usually start to diagnose a problem by looking at the last thing that was done to it. Let us know how you make out. If the problem is related to what the Factory did in removing end-shake, that is easy enough for you to fix at home.

Don't hesitate to PM me if you need any technical assistance in doing this.

Regards
Chief38

 

[bigggbbruce]

^This.. it's set to tight.

 

[Protocall_Design]

Sounds to me like there may be debris under the extractor. This is easily cleaned out with an old toothbrush. The dirt gets on there after firing and ejecting the spent cases. It falls out of the chambers onto the back of the extractor and is then trapped between it and the back of the cylinder where the extractor seats. This is a problem with all brands of revolver.

In your case it sounds like the ratchets are even with the center pin boss on the extractor. They should be a few thou. below the surface of the round boss. Two minutes on a lathe would fix that.
S&W may have fitted a new extractor to fix the end shake issue.

 

[smoothshooter]

Noticing a touch of binding on an L-frame when closing the cylinder.

Found a slight gouge in the blast shield where the ratchet teeth usually clear closing the cylinder. Now they barely pass without touching if I hold the cylinder forward when returning to battery; without doing that, they catch the shield.

Didn't used to do this. Was recently in for the "M" stamp, and the factory fixed a touch of endshake gratis. Set it to less than .001", nearer to zero.

Any chance these are related; if not, any suggestions?

I take it you mean the " recoil shield " ?
The blast shield is a small sheet metal plate sometimes attached to the underside of the top strap above the barrel / cylinder gap on some revolvers with alloy frame to avoid gas cutting.

 

[Hapworth]

I take it you mean the " recoil shield " ?
The blast shield is a small sheet metal plate sometimes attached to the underside of the top strap above the barrel / cylinder gap on some revolvers with alloy frame to avoid gas cutting.

Right you are -- meant the recoil shield, aka breechface. Thank you.

 

[Hapworth]

Reviving this thread. Same L-frame is binding under fire -- light loads, heavy loads, .38 Special, .357 Magnum -- get a few rounds through it and then binding unto non-rotation.

Clean; B-C gap is in spec but far from minimum; ejector rod is tight and straight; rotates fine empty, with live ammunition unfired, or with empties.

Only binds under fire. About convinced now that near zero endshake is the culprit and causing thermal expansion.

I don't have a yoke facing reamer. Any advice for properly -- and carefully -- removing a thousandth with what I have at hand: fine ceramic stones, various grit sandpaper, polish and a jeweler's micrometer?

 

[flintsghost]

With stones it is virtually impossible to remove material and keep the yoke face square, no matter how good you think you are at doing it. Beg, borrow, steal or buy a yoke face reamer. Take the cylinder off and use a right angle square and see if the yoke face may be out of square already. While S&W has never used shims in the past, they could have started so check that also. When I was in armorer school, S&W did not use yoke face reamers. Armorers were expected to get the yoke close with a fine barret file. if you're examination of the yoke end with a 90 degree square of some sort, shows it slightly out of square, you might be able to true it up a bit with a stone. Ceramic stones are so fine that they remove so little that you might want to invest in a fine India pillar file stone. India stones are what comes in the S&W armorers kit and they do work well.

 

[armorer951]

Have you checked the rear gage? (between the rear of the cylinder and the breechface)

While you do need some "endshake" or gage in there for the assy to operate properly, if you are at the outer limit here, about .064" or so, removal of material off of the yoke bbl could create issues/misfires.

 

[Hapworth]

Have you checked the rear gage? (between the rear of the cylinder and the breechface)

While you do need some "endshake" or gage in there for the assy to operate properly, if you are at the outer limit here, about .064" or so, removal of material off of the yoke bbl could create issues/misfires.

I have, although I'm using feeler gauges -- I don't have a go/no-go gauge. .060" fits; can't get anything past .065" through. I was under the impression that on S&Ws .060" to .067" was in spec; the go/no go gauges for sale are .060" and .068".

 

[armorer951]

You are correct, the specs are .060 - .068" on the 357 magnum series guns. Just me, but I like to keep this as close to the .060" measurement as possible, particularly with the frame mounted firing pin models.
If you decide to open this up a little....check to see what the front gage is before you start. The front gage should not go below .003 - .004" when the cylinder is pushed forward (at rest).

 

[armorer951]

I can send you a piloted yoke face reamer to borrow for a few days if you decide you need one.

 

[Hapworth]

...If you decide to open this up a little....check to see what the front gage is before you start. The front gage should not go below .003 - .004" when the cylinder is pushed forward (at rest).

Front gage is well above that; basically when I measure gap there's almost no difference when I measure gage, charge hole to charge hole.

I do have variation in front and rear gage of a few thousandths as I check each charge hole, but each "station" is nonetheless in spec, and the the yoke barrel is straight, so I'm assuming the cylinder faces are a little untrue, but again, still in spec.

 

[Hapworth]

I can send you a piloted yoke face reamer to borrow for a few days if you decide you need one.

Wish I could "Like" that one twice.

Many thanks -- I'll keep your gracious offer in mind if I try to correct this myself.

 

[BigBill]

I Luber the loc pin and star/arm with moly. It opens and closes so smooth now.