1858 throat and barrel size/ reaming questions

[curator]

diedinger,
Several years ago I had a small business accurizing cap & ball revolvers for the Cowboy shooters. I found many, many that had bore diameters of .460"++ and chamber diameters of .445" or occasionally even smaller. Reaming them to groove diameter plus .001" is not practical if there isn't enough metal left afterwards, particularly between chambers and under the cylinder lock mortise. You can still get reasonably good accuracy with these "mismatched" guns by loading them light and using a compressible "filler" under the ball, like Cream of Wheat cereal. The filler allows you to load the ball with minimum jump into the forcing cone then seals the powder gas preventing it from leaking down the grooves, keeping the ball centered in the bore. Not quite as good as having all the bore/groove/chamber dimensions match up, but it will make a $100 gun shoot pretty good.

 

[bigted]

So here is how i measure an odd rifled barrel.

First i measure the depth of the rifling and write this down in the middle of a piece of paper. I measure three slugs and each groove/ bore depth so i get a good average for a true number

Now i measure each slug from groove to the corresponding bore straight across from each other ... again i measure each slug and each groove/bore set.

Now i add the rifling depth to this number to get the groove diameter. I subtract the rifling depth to get the bore number.

Done several odd number groove barrels and wind up very close accuracy wise.

May help ... may not ... but there is my way.

Good luck ... and i also would be wary of thin cylinder walls ... especially between chamber holes.

 

[Scota4570]

I want to open up the chambers in an 1858. I see some use a 7/16 chucking reamer. That gives me pause. IF the alignment is not perfect you will get an oblong hole. I have a milling machine. Even so every chamber will would need to be carefully set up in the mill. Reamers and drills love to cut oversize. I'd hate to ruin the cylinder.

I had a thought. Why not make an adjustable brass lap? Make the cutting part short to minimize alignment issues. I could go around to each chamber then make the lap a hair larger and continue. I'd be taking only a couple of thousands. It should go reasonably fast. Even if it took a while I would have much more control.

Has anyone tried this approach?

 

[brayhaven]

Might also use an adjustable reamer.

 

[Scota4570]

I need an excuse to buy a set of adjustable reamers. I have had chatter issue with them in the past. They don't cut full depth, is the section on the nose of the adjustable reamers short enough to get sufficient depth of cut in the chamber?

 

[M. De Land]

The best way I accomplished reaming cylinder chamber mouths was to remove the barrel in a 58 Rem and make a reamer spud that went through the frame in place of the barrel. The spud had a long neck with a very close fit for the reamer shaft holding it on center with the cylinder chamber. The far end of the reamer shaft was put into my electric hand driver and each chamber was reamed the same. No chatter and clean metal taken from all around the chamber throat. This was about as close as one can get to actual line boring a chamber using the gun frame itself.
The open frame gun was done by hand and if careful can be felt through on hole center. It would be better to indicate hole center with a mill and ream if one has the proper cylinder fixture but is not necessary for a good job if your careful.

 

[M. De Land]

I need an excuse to buy a set of adjustable reamers. I have had chatter issue with them in the past. They don't cut full depth, is the section on the nose of the adjustable reamers short enough to get sufficient depth of cut in the chamber?

I have a set of adjustable reamers but for this job I prefer a simple fixed chucking reamer of the right diameter with a three or four inch shank. The shank length helps stay on center better, especially if your doing the job by hand and feeling it in. The reason a solid reamer is better for the job is you want to avoid any lateral flute movement which adjustable reamers must have, that encourages chatter, in my opinion.

 

[Rockvillerich]

I want to open up the chambers in an 1858. I see some use a 7/16 chucking reamer. That gives me pause. IF the alignment is not perfect you will get an oblong hole. I have a milling machine. Even so every chamber will would need to be carefully set up in the mill. Reamers and drills love to cut oversize. I'd hate to ruin the cylinder.

I had a thought. Why not make an adjustable brass lap? Make the cutting part short to minimize alignment issues. I could go around to each chamber then make the lap a hair larger and continue. I'd be taking only a couple of thousands. It should go reasonably fast. Even if it took a while I would have much more control.

Has anyone tried this approach?

I want to open up the chambers in an 1858. I see some use a 7/16 chucking reamer. That gives me pause. IF the alignment is not perfect you will get an oblong hole. I have a milling machine. Even so every chamber will would need to be carefully set up in the mill. Reamers and drills love to cut oversize. I'd hate to ruin the cylinder.

I had a thought. Why not make an adjustable brass lap? Make the cutting part short to minimize alignment issues. I could go around to each chamber then make the lap a hair larger and continue. I'd be taking only a couple of thousands. It should go reasonably fast. Even if it took a while I would have much more control.

Has anyone tried this approach?

Hi, I've used pilot reamers of appropriate sizes to open of cylinders of various revolvers with really good results. These reamers center themselves, and are available in about any size you'll need. Good luck!

 

[brayhaven]

Some adjustable reamers have more chatter issues than others, esp when used under power. I find the wedge adjusted ones are very good. Those that are compression adjusted do tend to chatter more. Chucking reamers can also be found in about any size in this range.

 

[Scota4570]

I reamed my 1858 Pedersoli's chambers to 0.452" . The groove diameter is 0.450" With 25 grains 3F and 0.454 balls it shot incredibly well. The best group of the day was five in 1" at 25 yards. All the groups were great, actually better than I shoot modern pistols.

 

[PluggedNickel]

Looking forward to the results. You didn't mention how accurate the revolvers are now, but I assume you feel there is room for improvement? At on time I had considered opening the cylinder charge holes to a depth of 1/2" and by a few 001" diameter. I Contacted Dave Mason, he replied he could send a custom made reamer for $85.00 to do this job. Decided I'd make do for now. I'm getting to the age where it is possible to have a pistol that will shoot better than I can.
It is of interest to note that according to the chart Zonie's posted the specs on those super target models they sell at a higher price are much better than the others!

"Dixie Remington New Model Army "Shooters" revolver"
bore = .440, grooves = .456 (5 grooves), chambers = .456

This is the only one listed where the groove diameter and chambers are equal! Also, note it is the only one with 5 grooves!
I have slugged my Uberti INOX NMA's and found the ball doesn't fill the groove all the way either. That may be on purpose, to reduce drag, and could improve velocity. On the other hand, doesn't it seem odd that the so called "Shooters" revolver slug does fill the groove, if this were the case? IIRC the Shooters revolvers have a longer barrel as well, but I could be wrong about that. It's been a while since I drooled over one.

After the headache I got reading Zonie's heavy on math post eased (tongue in check Zonie!)! I pondered how Wild Bill ever took out Davis Tutt at 75 yards with one shot to the heart. A lot of hand tuning and care to detail back in the day at Colt? Custom gunsmith work on his '51's? Who can say?
That is a very handy little tool you have there M. De Land!
Dledinger, nice to know there are others out there that go to so much trouble tinkering. I thought it was just me! LOL

 

[Scota4570]

I got two reamers here.
https://drillsandcutters.com/
Quality was good. Prices low, Shipping very fast.