Is this cylinder gap too large?

[Hapworth]

This is all great information. Thanks everyone! Waiting in anticipation for the feeler gauges to be delivered tomorrow.

Remember, b-c gap is measured with the cylinder held to the rear; check on each charge hole and from both sides of the gap...

...after you have checked, double-checked and triple-checked, then checked again, that the revolver is unloaded and safe to work on.

Depending on your measurements, if you're in spec and the revolver functions correctly under fire without spitting or shaving, I'm squarely in the camp of leaving it alone.

If you have an extraordinary gap or develop issues shooting, there are plenty of options and we can walk you through them, but basically it's about getting to a qualified revolversmith.

Long as you have the feeler gauges, check your endshake and headspace, too.

 

[rockquarry]

Yes, barrel-cylinder gap has a minimal impact on velocity. Ballistics by the Inch did a test on barrel-cylinder gap and velocity.



BBTI - Ballistics by the Inch :: Cylinder Gap

I'm not familiar with Ballistics By The Inch, but I don't believe it's possible to make a valid one-size-fits-all blanket statement about cylinder gap having minimal effect on muzzle velocity. Consider several revolvers from the same manufacturer that have average cylinder gaps and varying barrel lengths (3", 4", and 5") that give approximately "book velocity" (handloading manual references). Compare these figures with a 6 1/2" barreled revolver that has a wide cylinder gap of .010" - .011". The muzzle velocity on the latter gun is less than the velocity on the 3"-barreled gun.

No extensive testing here, just reasoning based on experience. That's also considering many changeable factors in play here. While it's true there are "fast" barrels and slow "barrels", that observable fact generally has much more signifcance with regard to rifle barrels and rifle ballistics than with revolver barrels.

 

[Paper Clip]

Remember, b-c gap is measured with the cylinder held to the rear; check on each charge hole and from both sides of the gap...

...after you have checked, double-checked and triple-checked, then checked again, that the revolver is unloaded and safe to work on.

Depending on your measurements, if you're in spec and the revolver functions correctly under fire without spitting or shaving, I'm squarely in the camp of leaving it alone.

If you have an extraordinary gap or develop issues shooting, there are plenty of options and we can walk you through them, but basically it's about getting to a qualified revolversmith.

Long as you have the feeler gauges, check your endshake and headspace, too.

I’m not a revolver newbie, but I am one when it comes to diagnosing this stuff. What does that mean and how do I check it?

 

[series guy]

Before you can accurately check the barrel cylinder gap you must insert feeler gauges of the correct thickness to set the rear gauge. Otherwise you may be pushing the cylinder back too close to the recoil shield.

 

[terry_tr6]

Feeler gauges! wow has it been a while since I've pulled mine out. Cars without points or plugs to gap every couple thousand miles, and selling the old triumph cycle so no valves to set every thousand or so miles.... I just recently got rid of my timing light and dwell meter....

 

[rockquarry]

I use a feeler gauge regularly in handloading, but rarely for checking cylinder gap. A feeler gauge is the easiest and fastest way of setting up a Forster case trimmer for a run of brass.

 

[Hapworth]

I’m not a revolver newbie, but I am one when it comes to diagnosing this stuff. What does that mean and how do I check it?

Endshake (known also as end play) is fore and aft play in the cylinder. A little (about .001") is necessary for proper function. Opinions vary on how much beyond that needs correction. Too much causes excessive batter under fire, possible binding and failed ignition.

You measure endshake by holding the cylinder forward and measuring the gap between the barrel and cylinder faces. Then hold the cylinder back and measure again. The difference is your endshake.

Headspace is the distance between rear of the cylinder and breech face (blast shield area by firing pin hole). Someone check me on this, but current spec I believe is .060"-.064".

 

[Benchrest1]

I have a old 686 no dash that has been shoot a lot. It has a gap of .010" and is still one of my best shooting guns.