Proper way to measure cylinder gap

[Lippy984]

Good morning all.
I’m sure this has been talked about a million times, but I’m having a hard time finding the actual method to measure barrel to cyl. gap on a Colt revolver. I know where to measure, but I’d like to know if the hammer should be down on a cone, Half cock with rearward pressure on the cylinder, or Full cock?

 

[Phil Coffins]

Half cock with the cylinder held back.

 

[Lippy984]

Ok, and that’s exactly what I did. My gap then measures .008”. However, I have an equal gap where the barrel lugs meet the frame. Is that acceptable, or does that need to be closed up, and fit the cylinder gap by removing material at the forcing cone?

 

[denster]

Ok, and that’s exactly what I did. My gap then measures .008”. However, I have an equal gap where the barrel lugs meet the frame. Is that acceptable, or does that need to be closed up, and fit the cylinder gap by removing material at the forcing cone?

If you have a gap where the barrel lug meets the frame you need to tap on the muzzle with a rubber or wood mallet to close that gap then measure the b/c gap in the manner stated ie:half cock cylinder held back.

 

[Lippy984]

If you have a gap where the barrel lug meets the frame you need to tap on the muzzle with a rubber or wood mallet to close that gap then measure the b/c gap in the manner stated ie:half cock cylinder held back.

No, this gap was created when I extended the arbor. Barrel locks up solid when the wedge is in

 

[denster]

No, this gap was created when I extended the arbor. Barrel locks up solid when the wedge is in

Then you extended the arbor too far. The arbor should bottom out at the same point where the lug meets the frame.

 

[bang]

Was this gap there before fitting shim?
Just out of curiosity are you sure the frame pins are not bottoming out?
If you used epox to glue in shim could there be some on top of shim?
Spin some steel wool in the hole to insure there is no glue build up.
If the gap persists pick the shim out and try again.

 

[Lippy984]

All I need to do it take down the brass button I installed on the arbor until the barrel lug meets the frame. So then my other question is once I do that, if I need to open up my barrel to cylinder gap, do I set that gap by filing material off of the forcing cone? Correct?

 

[denster]

All I need to do it take down the brass button I installed on the arbor until the barrel lug meets the frame. So then my other question is once I do that, if I need to open up my barrel to cylinder gap, do I set that gap by filing material off of the forcing cone? Correct?

To open it yes you would remove material from the rear of the barrel at the forcing cone. Before you get carried away though know that a .002 to .003 b/c gap is best for keeping fouling to a minimum.

 

[Lippy984]

Thank you

 

[bang]

May not need to do anything.

 

[Lippy984]

May not need to do anything.

Yeah, maybe I was just having a hard time figuring out the procedure...I just like to know exactly what I’m doing and why. It’s clear to me now

 

[M. De Land]

To open it yes you would remove material from the rear of the barrel at the forcing cone. Before you get carried away though know that a .002 to .003 b/c gap is best for keeping fouling to a minimum.

The trick at breech end barrel shortening is to keep it sqare and plumb, no easy task with a hand file. Its best done in a lathe or with down barrel rod and bushing tool made for the task and hand turned from the muzzle. The forcing cones are usually about half a ball diameter deep so that may need to be extended as well depending on how much barrel breech is removed. That also is best accomplished with the hand tool mentioned earlier.

 

[Bad Karma]

The trick at breech end barrel shortening is to keep it sqare and plumb, no easy task with a hand file. Its best done in a lathe or with down barrel rod and bushing tool made for the task and hand turned from the muzzle. The forcing cones are usually about half a ball diameter deep so that may need to be extended as well depending on how much barrel breech is removed. That also is best accomplished with the hand tool mentioned earlier.

4D Reamer Rentals can help with the tools M. De Land is speaking of. Depending upon how much you remove from the button you may arrive accidentally at the perfect cylinder gap. That would be nice...

 

[Lippy984]

4D Reamer Rentals can help with the tools M. De Land is speaking of. Depending upon how much you remove from the button you may arrive accidentally at the perfect cylinder gap. That would be nice...

After adjusting the button so the barrel just kisses the frame, I wound up with .005” with the cylinder held back. I’m content with that. It is slightly tighter (maybe .0005) on the bottom side of the barrel. It’s not perfect, but I’ll see how it shoots

 

[denster]

After adjusting the button so the barrel just kisses the frame, I wound up with .005” with the cylinder held back. I’m content with that. It is slightly tighter (maybe .0005) on the bottom side of the barrel. It’s not perfect, but I’ll see how it shoots

Never let the perfect be the enemy of the good.

 

[M. De Land]

After adjusting the button so the barrel just kisses the frame, I wound up with .005” with the cylinder held back. I’m content with that. It is slightly tighter (maybe .0005) on the bottom side of the barrel. It’s not perfect, but I’ll see how it shoots

That all changes any way when the ball slams into the forcing cone and the revolver flexes !