Revolver end shake/play and barrel/cylinder gap

[KYsquirrelsniper]

I was reading an article or post somewhere on the net a few days ago about end shake/play and barrel/cylinder gap and it's been on my mind ever since. Since rifles are my main area of knowledge, I thought I'd see what more experienced revolver shooters thought. So...

If I remember everything correctly, the article/post said that with the gun in full lock-up, the barrel/cylinder gap should be .006" at the most, with .002-.004" being preferred. It also said that preferably there would be zero end shake/play, with .001" being maximum.

Now, my thoughts while reading this was that those tolerances sound more like a custom job than a production revolver. The best I can remember though (should've bookmarked it :roll: ), it was talking about production guns too. I guess in a perfect world those tolerances would be nice, but I check over every revolver I buy and then check them periodically to see if they're loosening up. Although the article/post considered .006" barrel/cylinder gap maximum, I don't think I ever recall owning a production revolover with less than that, and most have been .006-.008". As for end shake/play, I've seen and had several that had zero play when new, but after a few hundred rounds, I've never had one remain perfectly tight, and most eventually loosen to .002-.004" of end shake/play. I guess if the article/post's tolerances are correct, then some of my guns need a little work, cause I can't stand knowing something isn't within spec, even if it does shoot okay

Any thoughts...

[Iowegan]

There are two sets of specs for firearms. One is a manufacturing standard and the other is a maximum spec, taking wear into consideration. Most companies don't reveal their "internal" manufacturing specs for fear of unjust warranty returns. They do publish their maximum specs because it might become a safety issue.

Each manufacturer will have different specs so stating a given cylinder gap or endshake is not valid for all brands or even models. I went to the S&W factory armorers course back in the early 70's. The spec for cylinder gap in K frames then was: .004~.008 with .006 being optimum and .010 being maximum. Endshake specs were 0~.001 with .002 as max.

New S&Ws commonly leave the factory with cylinder gaps and endshakes in excess of their old maximum standards. I guess this trend goes along with MIM parts and lower quality standards than they used for forged and machined parts.

Endshake is forward / rearward cylinder travel.  Ruger revolvers have a large bearing surface area so they rarely wear beyond specs. S&Ws have a very small bearing surface (the end of the yoke tube) so they tend to loosen up with shooting. Hot loads accelerate endshake wear. There is an easy fix for S&Ws. All you have to do is install endshake bearings (nothing more than .002" washers) available from Brownell's.

Cylinder gaps should be at least .004" in any revolver. If they are tighter, the shooting residue build-up on the cylinder face will cause the cylinder to drag on the back of the barrel. Excessive gaps will cause "spitting" from the gap and a loss of velocity. Accuracy may suffer too but normally not. If cylinder gaps are excessive, no amount of yoke stretching or shims will repair it. The only real fix is to turn the barrel in. That can create more problems than it fixes due to the "crushed thread" fit vs the old pinned barrels. Tightening the barrel a turn might result in a compression ring inside the rear of the barrel, front sight alignment problems and marred finish.

I recently chronoed two S&W 4" revolvers with 158 gr factory 357 Mag ammo. One was an older 686-2 with .006" gap and the other was a near-new 686 with a .012" gap. The velocity was 200 fps slower in the new gun and you could feel hot powder residue pelt your face from gap spitting. I guess the answer is to buy older S&Ws in like-new condition or buy Rugers.

[unspellable]

Cylinder gap varies depending on the make and type of revolver.  It's usually larger o nblack poder revovlers due to the potential crud build up.  On smokelss powder revolvers with fixed barrels the optimum is usually condsidered to be 0.006.  This depends a bit on use.  For social purposes reliability is paramount and you don't want to run the risk of crap binding up the cylinder.  For target or hunting (non-dangerous game) reliability is not quit as important and I like a narrower gap.

On a Dan Wesson the cylinder gap is adjustable and can be set for the intended use.  Factory nominal for the Super Mags is 0.003 and for the 357, 44 mag, tec., it's 0.006.

The presence of end play accelerates the rate rate which end play increases, so if you have any, especially on a S&W it should be corrected.

It's an unfortunate aspect of modern life that more end play and cylinder gap comes out of the factory than used to be the case.

[Black Jaque Janaviac]

How do you measure these things?  I've got a calipers and a micrometer.  The micrometer I would think would be useless.  I can imagine a very crude way to measure endshake with a caliper - but I've no idea how to get cylinder gap.

The way I'm thinking of measuring endshake is to hold the caliper alongside the barrel and push the pin down onto the end of the cylinder.  Then push the cylinder forward and see how much it pushes the pin forward.  Seems kinda sloppy, and I'd bet I'd get more than a few thou variation between measurements so the "noise" would be louder than the actual endshake.

[Iowegan]

BJJ, Pretty easy...get a pocket knife type gap gauge. Insert the blade between the cylinder face and the back of the barrel. Hold the cylinder to the rear and find the thickest blade that will fit with friction. Hold the cylinder forward and repeat. Subtract the smallest from the largest. That will be endshake. Cylinder gap will be the largest of the two measurements.

[Black Jaque Janaviac]

Ahh! the proper tool for the job.  There's gotta be a way one can accomplish this using only a hammer! :grin:

[safetysheriff]

It's bein' done again!    :shock:   Stop sugar-coating it and give it to him straight.  :eek:    Buy yourself a single-action Ruger Super Blackhawk or a double-action GP-100 and you'll have a handgun that will run with near-max loads for thousands upon thousands of rounds.    Just take some feeler gauges with you when you buy the piece -- whether at a show or a dealer.    Get one with minimal end-shake --- period.   Then you'll be in the ballpark.    If you buy a Smith' you run more of a chance of visiting the repair shop if you fire heavy loads regularly...     If you don't like heavy loads and you don't want to get up too much off your wallet then you may be able to get by with a TTtttttt................ :eek:     TTTTttttttttaaaauuur :shock:  :shock:  you know the one I mean!

SS'   :wink: