Cylinder Throating

[ADK Bigfoot]

Is there anyone out there who can open up cap and ball chamber throats? Mine has .446 throats and I would like them to be .451.

ADK Bigfoot

 

[64Springer]

Make a chicken plucker/flapper wheel and hone those things out.

A machine shop would have to dial in each chamber and either ream them out or circular mill them out with the side of an endmill.

Either way it's probably hundreds in machine/set-up/labor costs.

 

[Jim in Wisconsin]

I wanted to do that too, I bought a 29/64 chucking reamer which is .453. A little bigger than what I wanted, but pretty close. I have a small milling machine and used that to be sure I was over center on each one. I ran the reamer down only as far as a seated ball would be, (don't remember how far exactly). That worked out real nice and seemed to make a difference in accuracy.

 

[M. De Land]

Is there anyone out there who can open up cap and ball chamber throats? Mine has .446 throats and I would like them to be .451.

ADK Bigfoot

The most accurate way to do this is to make a close fitting reamer spud that threads into the barrel hole in the frame and directs the reamer squarely into the chamber mouths at each bolt lock up. I have done the job both by hole locating and making a frame reamer spud. The later is the most accurate akin to line boring and the former is only as accurate as the original chamber location in the cylinder. I don't provide this service professionally but have used both methods for my personal guns.

 

[Jim in Wisconsin]

You mean with the barrel removed, I am sure. That would for sure be the right way (assuming the bore is concentric with the threads - which it will be I think). A tool sharpening shop could take a little off the reamer if you really wanted .451
With that rigid setup and a sharp reamer, it could probably be turned by hand. It's taking only a small amount out.

How tight are those barrels in the frame? I have been afraid to try taking one out.

 

[M. De Land]

You mean with the barrel removed, I am sure. That would for sure be the right way (assuming the bore is concentric with the threads - which it will be I think). A tool sharpening shop could take a little off the reamer if you really wanted .451
With that rigid setup and a sharp reamer, it could probably be turned by hand. It's taking only a small amount out.

How tight are those barrels in the frame? I have been afraid to try taking one out.

I was referring to a sold frame gun with the spud reference fitting the barrel hole through the frame. An open frame gun would be relegated to the current chamber centering before each ream job.
The last one I did I used my drill press to hold the reamer shank and a dual axis mill table to get precise and square chamber centering on x-y axis. The depth was set with a plug gauge and the quill lock on the drill press. I used a plug gauge in the drill press quill to find center on each chamber then remove the plug gauge and reamed the chamber. Repeat six times but it is only as accurate as the chamber hole centering from the factory. I think I have some photos of the reaming some where here.
The last picture is a steel stop plug to limit reaming depth and make each chamber exactly alike.
Click on the photo to enlarge.

 

[M. De Land]

You mean with the barrel removed, I am sure. That would for sure be the right way (assuming the bore is concentric with the threads - which it will be I think). A tool sharpening shop could take a little off the reamer if you really wanted .451
With that rigid setup and a sharp reamer, it could probably be turned by hand. It's taking only a small amount out.

How tight are those barrels in the frame? I have been afraid to try taking one out.

One needs a good padded bench vice or barrel vice and strap wrench to remove the barrel from a frame. One does not want to remove the cylinder and poke a stick of wood through the frame to lever the barrel off. That's a very good way to bend out of square or break a frame. The correct method is to fabricate a strap wrench that will clamp over the outside of the cylinder window on the flat sides of the lower frame and top strap clamping the frame flatly and evenly. Some times a bit of heat before applying pressure will help break the thread purchase especially if loc-tite was used to secure the barrel.
I just turn the pulley in the top of the drill press when reaming or if in a hurry one can turn the power on. The chucking reamers will cut a round hole and leave it well finished with just a bit of polishing with 400 grit emery paper if one wishes.
A word of caution when setting up the cylinder in the v blocks on the mill table. Use shim stock to prevent denting the cylinder finish and check cylinder for perpendicular as they very often are not and need to be shimmed in parallel to the chambers.
The plug gauge check will reveal this very quickly as they go down inside each chamber where as a hole center finder does not check for parallel.

 

[M. De Land]

One needs a good padded bench vice or barrel vice and strap wrench to remove the barrel from a frame. One does not want to remove the cylinder and poke a stick of wood through the frame to lever the barrel off. That's a very good way to bend out of square or break a frame. The correct method is to fabricate a strap wrench that will clamp over the outside of the cylinder window on the flat sides of the lower frame and top strap clamping the frame flatly and evenly. Some times a bit of heat before applying pressure will help break the thread purchase especially if loc-tite was used to secure the barrel.
I just turn the pulley in the top of the drill press when reaming or if in a hurry one can turn the power on. The chucking reamers will cut a round hole and leave it well finished with just a bit of polishing with 400 grit emery paper if one wishes.
A word of caution when setting up the cylinder in the v blocks on the mill table. Use shim stock to prevent denting the cylinder finish and check cylinder for perpendicular as they very often are not and need to be shimmed in parallel to the chambers.
The plug gauge check will reveal this very quickly as they go down inside each chamber where as a hole center finder does not check for parallel.

I should have mentioned that I have actually done a reaming job by hand using the feel of cut to direct the reamer. It was tedious and worried me no end as I could feel the reamer bite in more in some areas than others but the finish job turned out quite satisfactory. What I was feeling when the reamer bit in more in some spots was two fold, out of roundness in the existing chamber and when I was canting the reamer out of parallel, hence "feeling" it in.
As I was finishing the hand reaming I noted some chatter marks in one of the chamber walls and thought OH No I screwed this job up but then looking closer I noticed the chatter marks had bluing in the bottom of them meaning it came that way from the factory not my reamer. My reamer had actually cleared away part of the tops off the factory induced chatter. The gun doensn't seem to care but it drives me nuts to find these imperfections when working them over.

 

[garypl]

I have sent a few unmentionable cylinders to a guy in NC to have the throats honed to size - made a noticeable difference in accuracy and leading in the barrel. Don't see why he couldn't do a BP revolver sylinder. He is in the Cast Boolits forum.

 

[64Springer]

Bullets...

 

[edrutecki]

Contact Hahn Machine Works. He has done them for me in the past. Slug your barrel if you have not already done so. The cylinder needs to be reamed a couple thousands OVER groove diameter. Sure makes a big difference in grouping!

 

[M. De Land]

Contact Hahn Machine Works. He has done them for me in the past. Slug your barrel if you have not already done so. The cylinder needs to be reamed a couple thousands OVER groove diameter. Sure makes a big difference in grouping!

Yeah that'll work. I have preferred at or no more than .001 over groove diameter for best accuracy and low pressure.
Getting an accurate groove diameter out of some of these revolver barrels of uneven land count is problematic for most folks without a Tri-mic or Powley gauge so as to get a good read on what the chamber mouth should be.
I don't know the reason for the undersized chamber mouth diameters. Apparently ball or bullet base "bump up" is figured into the design.

 

[hawkeye2]

Another vote for Hahn Machine works. Charlie has done quite a few for me with the last one a few years ago at $35.

 

[M. De Land]

Another vote for Hahn Machine works. Charlie has done quite a few for me with the last one a few years ago at $35.

Wow what a low price. How uniform are all the throat diameters with each other. Plug gauge check?

 

[French Colonial]

You can buy reamers pretty cheap and they work well. You do not have to buy an expensive one if your only going to do one or two cylinders.

I used one on my unmentionable Ruger in 45 colt and it really made a difference.

 

[nkbj]

For the Pietta undersized chambers I started using soft cast semi-wadcutters and round noses and sized the bases down to slip into the chambers to establish precise alignment. The front ends of bullets are left big to shear the same as does round ball. That way I could turn Pietta's faux pas to my advantage.