speced out the 36 cal 1862 tonight

[M. De Land]

Bore is .366, grooves are .3745 and the chambers are .372. Checked with plug gauges and a bore slug.
I have a .376 reamer and think I'll open up all the chambers to that diameter and get a Lee mold of .378-.380 if they sell one in that range. That will put the chamber throats at .0015 larger than the groove diameter which should be about right. Mike D.

 

[swathdiver]

Lee does make a .380 double cavity round ball mold, 90423.

From what I've read, chambers shouldn't be more than .001 or .002 over groove diameter to keep pressures reasonable.

Maybe others with more experience will chime in, or maybe you can teach me the why.

 

[M. De Land]

Chambers set up ideally are at and no more than .001 over groove diameter. I think with this gun I will be fine at .0015 over groove diameter.
I noticed when I checked all five chambers with the plug gauge that two of them are slightly tighter than the rest so it will be good to make them all the same.
These production gun cylinders are gang reamed and they will all be a bit different from their mates so it actually is a good thing for them to be undersized when one wants to fine tune them and make all the same with a single reamer.
The trick is to get them dead nuts on center before the reamer job. The Colts do not have a solid frame from which to make a centering spud for the reamer so one can line bore through the frame. I will have to set up in the mill and use the plug gauge in the mill quill to find center on each hole,lock into position, replace the plug gauge with the reamer and cut to the bottom of the chamber. Each hole will need to be centered individually before being reamed. Mike D.

 

[Zonie]

You can indicate the chamber diameter in to zero before reaming or, if you have a floating reamer head, let the reamer find its own center.

With a floating head, indicating or plugging as you say you may do isn't necessary.

Another technique is to hand ream the chambers.
Again, hand reaming will allow the reamer to centralize itself to the existing hole so indicating the chamber in to zero isn't needed.

 

[swathdiver]

I'm fortunate in that my ASM Pocket has .374 chambers, .365 lands and .372 grooves. It also has a 1:21 twist. .380 round ball is perfect but have to find that old .380 conical mold for it someday or use Kaidos and load off frame.

But do plan on doing same work next year on my Pietta Remingtons.

 

[M. De Land]

Two problems I have run into is that run out is much greater when one tries to hand ream a blind hole without some means of reamer alignment and shank support because they cut along their length as well as the end. I have run into this just about every time I have reamed a shot gun choke and it takes some work to get things coaxial again even if you don't set up a chatter. You get a chatter going and it makes it double hard to get things straightened out.
I use a self centering floating reamer holder routinely when chamber reaming although the one I have is not set up for my mill but rather the tail stock of my lathe. These floating holders are designed for reamers with a pilot to steer the front end and will not hold center with a chucking reamer very well in a blind hole especially if one hits a hard spot or inclusion in what is being reamed.
The plug gauge will not only center the hole but will center the axis of the chamber making it coaxial with the quill and the reamer it will hold.
When one is machining you have to decide to turn the work or the cutting tool and each situation will determine which has the most advantage. Mike D.

 

[t.l.a.r. eng]

Lee makes a .380 round ball mould that should work.
You may have already noticed the chambers are out of round from the rolling process they use to engrave the scene on the cylinder. Mine had two chambers .002 out of round. Since reaming to .002 over groove, it made a new revolver out of it, fun to shoot instead of just being a door stop.
I beveled the entrance to the chambers also.

 

[M. De Land]

I think I will make a square sided aluminum collet and split the center hole on one side for the cylinder hold fixture to be used in the mill vice. This will hold the cylinder radially and keep the chamber holes from deforming by vice pressure.
I considered using the four jaw in my lathe but think this will be a better means of reaming on center without chamber hole distortion in this five chamber cylinder that is not round but pentagonal from the flute profile it has. It should be easy to center each on the mill table X-Y axis with the plug gauge instead of the center finders I have. Either will work but I think the plug gauge will be faster.
With this fixture I will not have to re-set the cylinder for each ream but only change back to the plug gauge in the mill quill for each new chamber centering.This will make all chambers coaxial with each other. Mike D.

 

[t.l.a.r. eng]

The fixture is no doubt the more accurate way to go than hand reaming, although it may not be that critical.

You didn't say but is the revolver a Pietta? If so you may want to fix the forcing cone and the muzzle end of the barrel. Pietta uses a very short abrupt "forcing cone" that usually isn't that smooth. I made the tools to make a proper 11 degree forcing cone of at least 1/4 inch and a it made a real difference in the accuracy of the revolver.
I made a short aluminum piece to fit the barrel and cylinder when the barrel was installed to check the timing and locking of the cylinder, mine needed a new bolt reshaped to lock the cylinder correctly.
Straightening the muzzle end of the barrel and breaking the sharp edges of the rifling with a lap also helped tremendously.
Just something to consider.

 

[M. De Land]

Thanks, good suggestions! This gun is made by Uberti for Navy Arms.
The forcing cone looks to be correct as it is, judging from a ball I dropped in and it seats 3/4's of the way into the bore but the crown could stand a chamfer.
I have the proper tools from Brownells for cone and crown reaming that works beautifully. It consists of an aluminum T handled rod which centers the bore with brass bushings fore and aft making the reamer cut concentric supported from both ends. I have both eight degree and eleven degree cone cutters and three 45 degree crown cutters (.38,.44 and .45 cal) along with corresponding brass laps.
I think for ball shooting the short forcing cone, if well centered, is to be preferred as the jump to rifling is significantly shorter than with the eleven degree cutter that is superior for lead conicals.
I once lengthened a forcing cone in another of my revolvers and felt accuracy went the other way a bit, for ball shooting. Mike D.

 

[AZbpBurner]

Upon completion of all your handiwork, I'd be interested in seeing the before & after target results.