Barrel / cylinder clerarance

J

Jeryray

New member
I checked my clearance between barrel cone and the cylinder.

Use two pieces of 20lb paper that measure .01 or 1/128.

Does that seem normal?
 
.01 = 1/100

this was a test right???

I seem to remember about .005" or .008" on one of my firearms. That was a long time ago.
 
Last edited:
if both pieces of paper measured at .001 and that was as much as you could fit in there, seems a bit tight for my taste. do you get any binding when the cylinder rotates? do you have access to some feeler gauges? to take a more accurate reading? i mean .001 is a bit tight but if it rotating freely and all i wouldn't worry to much. normally you would have anywhere from .004 - .008 from factory. repairs are normally required when you are in the .010 and above then that would be unsafe and may cause spiting.
 
I think my measurement technique may be off, I can "see" a space between the barrel and the cylinder. And the two pieces of paper can fir their.

Just don't remember that much space.

Recently a gunsmith "shimmed" the cylinder because it had movement.
Though I needed a barrell, but is shoots ok now.

Just wondering.

Have to look through my garage, used to have gauges, must be there somewhere...

Thanks
 
Found my feeler gauges, but the smallest is .012 /.3mm.

It fits if I close the cylinder, but it;s snug, so it;s less than .012 and I can see a little light between.

SO maybe it's ok?
 
Hey guys, I don't see anywhere where Jeryray said .001" or one thousandth.

He said " .01" which is .010" or 10 thousandths.

Jeryray, your method is not bad if you have an accurate way to measure the paper thickness, of course feeler gages are better. What had me scratching my head was the 1/128". Don't know how you arrived at that... New math???
 
Last edited:
What gun are you measuring?
Usually the max. for cylinder gap is .008 and .003 in min.
Shimming a cylinder usually is to cure excessive headspace. for barrel/cylinder gap the
barrel is set back one thread and the face of the forcing cone is machined to set that gap.
 
Barrel-cylinder gap should be between .006" and .012". Any tighter and the cylinder will bind when firing due to heat. Any wider and you have a spitting nightmare. So you are about .010"-.012" from the sound of it. Shoot it.
 
Jeryray, if you already had a smith shim the cylinder, you should be fine. It sounds like you are close to max spec.

Measuring tenths (.0001) or even thousandths (.001) is part art and part science. Skill will affect the recorded measurement. Gauges can compress, parts can spread, and temperature can also play in.
With feeler gauges, you want a very slight drag. Just touching. No clearance and no interference. This will give you the best number. Closing the cylinder can mask an interference, which you correctly determined makes it tighter than .012.
You can find a nice set for less than 20 dollars that will go down to .002 or .0025 and up to .030. Very useful if you tinker.

If you have say .009 or .010, and aren't spitting lead, I say shoot it, and keep an eye out. If that gap increases, or you see lead, investigate further.

Merry Christmas

Rich
 
SAAMI test barrels with vents to simulate barrel/cylinder gap use 0.008", but you see a bigger range than that. I had 0.002" on a S&W I got in a trade, and it had some cylinder face scoring, so it is correct that if you fire fast enough to heat up such a gun, you will find that number is too small and can allow dragging. 0.006" is, IIRC, the thickness of the feeler gauge Dan Wesson provided for setting the gap in their change-barrel revolvers.

If your feeler gauge is snug at 0.012", it is probably a little over. You are probably in the 0.011-0.012" range.
 
You must log in or register to reply here.
Back
Top