Can a cylinder gap be too small?

[Kizmo]

I'm a newbie here, and this is my first "real" post. Forgive me if this is a stupid question.

About two weeks ago, I got a brand new 629-6 (Made Dec. 2013) 6" half lug. I already had a 29-10 Classic. Comparing the cylinder gaps of the two, I really can't see any daylight at all on the 629, whereas the 29-10 has a readily visible, but thin, gap. "Huh?", I said to myself, and proceeded to shoot 300 rounds of WWB out of the 629 in a week. I figured that as long as the cylinder rotates freely, then no problemo.

Well, today, my business partner showed me his brand new 629 Classic Deluxe 6 1/2" full lug. As I was drooling over it, I noticed his cylinder gap is pretty much like the one on my 29-10. Real thin, but no problem seeing daylight through it.

Is this an issue I should be concerned about?

 

[ronnie gore]

gap

when I get a new to me revolver if the light is the same on every chamber I do nothing, when it is not I install the bushings from brownell's
easy job.

 

[arjay]

Tighter is better as long as it doesn't rub against the forcing cone.

 

[OKFC05]

Try pushing the cylinder back and measuring the gap with a feeler gauge. Even on a tight one, there should be at least a couple thousandths. Typically .004" or more. Rarely they come too tight from the factory, and they will correct it. The problem with too tight ( .001) is that they bind up quickly with carbon fouling in heavy use.
Measure the gap with the cylinder pushed forward. If the difference is more than 0.002", you have an endshake problem that needs correcting.

Welcome to the forum.

 

[Neumann]

Normal for a S&W is .003" to 0.007". This is with the cylinder pressed back toward the recoil plate, using a feeler gauge. If it is too tight, normal powder and lead deposits may interfere with rotation. Too loose, and you get too much spatter from the sides. Gap has very little effect on velocity.

 

[05CarbonDRZ]

The only problem you may have is shooting lead ammo and the cylinder getting caked with powder/lead.It will make the cylinder hard to rotate.

Edit:Wow 3 posts all at the same time

 

[Hapworth]

Provided there's no binding under dry or live fire, you're fine. Obviously if the cylinder and forcing cone are touching, this is a problem.

Too, a very tight b-c gap (say, .001" to .002") can bind more easily under fire as fouling quickly builds up.

Generally, .003" to .006" is considered an ideal gap. You measure by holding the cylinder back and sliding feeler gauges between the barrel and cylinder; the largest gauge that will easily slide in is your gap. Do this on each chamber as sometimes there are variations; too great a variation can mean somethings out of true.

 

[Kizmo]

Wow. You guys are great. Thanks everybody. I generally don't shoot lead bullets in my .44's (also have an Anaconda). I remember reading John Ross's essay on his Performance Center .500's about the barrel nut being necessary to get such a tight cylinder gap. Trust me, this 629 did it without a nut.

I will get myself a gauge (I assume you can get them from Midway or a similar place). I also hadn't thought about the possibility of the gap being different for different chambers. Again, I'm a newbie.

 

[Hapworth]

Measure the gap with the cylinder pushed forward. If the difference is more than 0.002", you have an endshake problem that needs correcting.

I'm open to higher knowledge, but are you sure? The Kuhnhausen manual recommends correcting endshake after .006".

 

[canvsbk]

Tighter is better as long as it doesn't rub against the forcing cone.

Not true. Beware of internet advise.

.004-.006 is ideal.

My 686ssr came from the factory @ .0015. Sometimes I could shoot a full dozen shots before it locked up.
Get some feeler gauges....

 

[Hapworth]

Not true. Beware of internet advise.

.004-.006 is ideal.

My 686ssr came from the factory @ .0015. Sometimes I could shoot a full dozen shots before it locked up.
Get some feeler gauges....

Well, both are true depending on intended use. A defense gun? You bet b-c gap can be too narrow if it quickly binds from fouling.

A bullseye competition gun? You can get away with a very narrow gap because fire is limited, and might see accuracy benefits, too.

 

[NYlakesider]

Wow. You guys are great. Thanks everybody. I generally don't shoot lead bullets in my .44's (also have an Anaconda). I remember reading John Ross's essay on his Performance Center .500's about the barrel nut being necessary to get such a tight cylinder gap. Trust me, this 629 did it without a nut.

I will get myself a gauge (I assume you can get them from Midway or a similar place). I also hadn't thought about the possibility of the gap being different for different chambers. Again, I'm a newbie.

Most any auto supply store will have feeler gauges or well equipped big box store-- Lowes, Home Depot!

 

[Gunhacker]

The ammo doesn't have to be loaded with lead bullets... you can get some binding with ammo loaded with a powder that burns particularly dirty leaving a lot of burnt/un-burnt powder residue. I ran into that with some cheap practice ammo... I no longer remember what brand it was.

You just need a standard flat blade feeler gauge set that has blades in the .003 -.007 range, usually available at auto parts stores.

You measure as a go/no-go, if the .003 doesn't fit, the gap is typically too tight, if anything above .007 fits, the gap is too big (maybe)... just because S&W specs are between .003 - .007, there's nothing that says that you can't get away with having it slightly out of spec and not have any issues.

 

[Fishinfool]

Kizmo - You can purchase flat steel feeler gauges from any auto parts or sears / walmart cheap. Same as you would use for gapping spark plugs. R/E your gun - If you have fired 300 rounds of ammo without any binding, I think you are good to go as is. If you notice any binding after firing numerous shots, a bronze bore brush soaked with a little bore cleaner, brushed across the cylinder face should get you going again. Personally, I like a tight gap, as long as binding is not a problem.

Larry

 

[Hapworth]

You just need a standard flat blade feeler gauge set that has blades in the .003 -.007 range, usually available at auto parts stores.

You measure as a go/no-go, if the .003 doesn't fit, the gap is typically too tight, if anything above .007 fits, the gap is too big (maybe)... just because S&W specs are between .003 - .007, there's nothing that says that you can't get away with having it slightly out of spec and not have any issues.

S&W's old school specs actually allowed for a gap out to .010", and these days .012" is officially in spec.

 

[Kizmo]

Thanks fellas. I'll hit the auto parts stores tomorrow.

This 629 is my new "go everywhere in the woods with me" gun. It's just too humid and rainy in the summertime for my 29-10. I hog hunt with handguns year round, and run into rattlesnakes frequently. This year alone, my 29-10 saved me from a big rattlesnake and my Ruger .454 saved me from a charging sow. Fortunately, that's about all the bad stuff we run into down here, but, still, locking up could be a bad scenario.

 

[OKFC05]

I'm open to higher knowledge, but are you sure? The Kuhnhausen manual recommends correcting endshake after .006".

Read the whole paragraph:

"I define GROSS CYLINDER ENDSHAKE as enough play that the cylinder hits the barrel OR... .006"............,correct.....
leaving .001" endshake clearance."

This is supposed to be a new gun, and should definitely NOT have "GROSS endshake clearance." Since the washers come in .002" , it is difficult to change endshake under .002" without the tools to stretch the yoke. It is simple to change washers, and I keep my well-worn competition revolvers at .002" or so.

 

[Hapworth]

Read the whole paragraph:

"I define GROSS CYLINDER ENDSHAKE as enough play that the cylinder hits the barrel OR... .006"............,correct.....
leaving .001" endshake clearance."

This is supposed to be a new gun, and should definitely NOT have "GROSS endshake clearance." Since the washers come in .002" , it is difficult to change endshake under .002" without the tools to stretch the yoke. It is simple to change washers, and I keep my well-worn competition revolvers at .002" or so.

I have read the whole paragraph. You don't quite reproduce it accurately: it recommends correction beyond .006", not at.

Neither number, though, is the much narrower .0021" or greater that you define as an endshake problem in need of correction.

I was curious about the discrepancy between your metrics and those of the shop manual, and remain so.

 

[OKFC05]

I have read the whole paragraph. You don't quite reproduce it accurately: it recommends correction beyond .006", not at.

Neither number, though, is the much narrower .0021" or greater that you define as an endshake problem in need of correction.

I was curious about the discrepancy between your metrics and those of the shop manual, and remain so.

Well, OK, if you want to wait until the barrel scrapes the cylinder, go ahead. IMHO, that's pointless, if you do any amount of shooting that matters.
The model 66 I am running in competition now has a gap with cylinder pushed back of .006 and endplay of about .0015" with two 0.002 washers installed. With the washers out, I can only run a few stages before the crud buildup in the gap starts to change the feel of the double action trigger pull. If that kind of performance in a revolver meets your needs, be my guest. It does not meet mine, nor any of the other competition revolver shooters I know.

Maybe it's a difference in attitude about machinery in general. I had to pull the heads on my classic chevy to replace a head gasket, and while I was in there I had the heads and manifold machined to blueprint specs, replaced the valve springs, and had the valves ground with a 3-angle blueprint job, bringing the seats out to spec. None of which was required if you only considered the "maximum allowable wear before discarding" in the shop manual. I want any machine I use to work smoothly and efficiently.

 

[Morgan88]

For what it's worth.
I found a flat steel feeler gauge out in the garage. The thinnest one is a 0.006.
In my EAA 357 it fit between the cylinder and forcing cone with a little work.
In my S & W model 60(no dash) 38 special it wouldn't fit and I didn't force it. I tried several places on the cylinder. No go.