Head space on Mod 36

[H Richard]

I just acquired a flat latch Mod 36, from 1965. With some brands of ammo, the rim thickness is actually causing binding by dragging on the recoil shield. Can anyone give me the measurement for clearance between the cylinder face and recoil shield? I believe this is corrected by corrected by removing a little from the end of the yoke?

 

[WR Moore]

Headspace for non-recessed S&W's is 0.060-0.068 inches.

Way before you start whittling on parts, clean the cylinder thoroughly, including under the extractor and down inside the cylinder where the yoke barrel fits. Then, and only then try to measure headspace.

Headspace is actually controlled by the center section of the ejector, forward movement of the cylinder is controlled by the yoke barrel as you describe. If a properly cleaned weapon has insufficient headspace, it needs to go back to the factory.

 

[500 Magnum Nut]

I believe this is corrected by corrected by removing a little from the end of the yoke?

No, this will affect endshake & may affect the cylinder striking the forcing cone. The hub of the ejector controls head space.
In the faq there is head space tollerances listed for different calibers.

Like already mentioned. Clean it up good, everywhere before going to the next level.

 

[Alk8944]

First, using automotive feeler guages, check the clearance between the back of the cylinder and the breech face. If it falls in the range WR Moore lists (actually .062 to .070 as I recall since maximum rim thickness is .060 and there needs to be some clearance) then the problem lies with your ammunition, not the gun.

If the clearance is less than .060 then this can be fixed only two ways. First is replacement of the extractor. This is a factory fit part only and they may, or not, have one. Probably not. The second is to find a gunsmith that has a .38 Spl chamber reamer and have him deepen the rim-cut area of the extractor and cylinder a few thousandths until a .005 feeler guage will fit between a case head and the breech face.

There is one other thing that could be the problem. If you have been dry-firing the gun much this will develop a burr around the firing pin hole and the cases are catching on this burr. Inspect the firing pin bushing, and if it is burred it is easy to stone the burr off with a fine Aluminum Oxide (Corundum) stone.

My bets are actually on this last being the problem as the gun developing insufficient headspace during it's life are extremely unlikely. If it had, then it will have quite a bit of endshake.

And, BTW, you can get a feeler guage set at any auto parts store, but Harbor Freight sells them (.0015 to .025) for something like 98 cents.

 

[WR Moore]

In the extremely unlikely event that the weapon actually did leave the factory with below minimum headspace there is another option if the piece doesn't have recessed chambers: face off the rear of the cylinder assembly the required amount. THIS IS A CHOICE WITH NO CHANCE OF REPAIR IF PERFORMED UN-NEEDED OR INCORRECTLY!

 

[redhawk444]

Clean it up real good first...especially under the ejector star, then see what you got.

I would bet that you will have solved your problem.

 

[aquagear]

Check to see if the case heads hit on both sides of the recoil shield or just one, if it occurs on only one side it could be a bent crane. The other check, and I suggest you do both, with the hammer down and trigger back check the cylinder gap on both sides of the forcing cone using a good set of feeler gages.If the gap is different by a significant amount it is a bent crane. you can try to fix it yourself or send it back to Smith & Wesson.

 

[Alk8944]

The other check, and I suggest you do both, with the hammer down and trigger back check the cylinder gap on both sides of the forcing cone using a good set of feeler gages.If the gap is different by a significant amount it is a bent crane. you can try to fix it yourself or send it back to Smith & Wesson.

aquagear,

Unfortunately you are incorrect on this. An uneven B-C gap, rather than being a defect, is nearly universally found on S&W revolvers. The B-C gap, at least until CNC and MIM parts, is set by the fitter using a safe-edged flat file while the gun is held muzzle down by the barrel in a vice. Filing the end of the barrel completely evenly is an art not often fully realized.

The only way to check yoke alignment is with a yoke alignment arbor which is inserted in the yoke which is then installed in the frame. Using a babbitt bar and hardwood or hard plastic wedges the yoke barrel is then bent up, down, left or right as needed so that when the yoke is held tight against the frame the end of the arbor will freely enter the center pin hole in the breech face.

To suggest the yoke is bent using your criteria reflects a lack of understanding of the mechanism and factory assembly methods.

 

[H Richard]

The Head Space measured .067", but I did find a very small burr in the firing pin bushing from dry firing. That has been removed and everything works fine. Thanks for the information.