I'll type a little about the reaming process and the accompanying accuracy results.
I have a milling machine fer starters. I got it initially to cut perfect dovetails into muzzleloader barrels when I was making half stock black powder traditional rifles.
Along the way I'd notice that cleaning my Colts cap&ballers that I could see with a pen light down the barrel and tell the chambers were smaller than the barrel grooves. Reading gun magazines at work all the time (
I had a job whereas I could and did read read read) The thing was "revolvers" back then. Cartridge guns mostly. The adage was that with lead bullets too loose it made leading and too tight made leading in the barrels. The thing was....lead bullets needed .000,-.001's-.003's inch over size fer the grooves in the barrels.
When I looked down the barrels of my cap&ballers ,shooting lead balls or conicals, I would see silver from the light bouncing off the face of the cylinder even if the cylinder was black. You know...… seeing the silver around the chamber hole told me the chambers were smaller than the grooves in the barrels. If the chamber was aligned well the silver was around the entire chamber. If the chamber was out of alignment I'd see like a sliver of silver on one side or the other of the chamber looking down the barrel. When I'd advise folks about that I'd term it as the ,"silver moon of misalignment" .
Anywhooooo….I lived with the smaller chambers for years thunkin that must be the way it should be. I new better the whole time but didn't want to mess with my chambers , but it did bother me.
One day I had a milling machine delivered and got a mess of bottom cutting end mills and some dovetail cutters. I was cleaning my 1851 Navy in my shop and......looked at that danged cylinder and thought, " I'll make you freakin right or die doing it or ruin yer ass and throw you in the corn field".
I got out a .375 in. end mill and stuck it in it's collet(the things the end mills go into) and draw it up in the machine with the top bolt. All set with a new end mill drawn up in the new milling machine and then thunked about how to center the end mill to the chamber to enlarge it. The chamber was padded and already put in the machinist vise nice and straight.
That meant taking the collet with the end mill out and installing the drill chuck with something to help align the danged chamer thing.
I made a pointer then from drill stock that was the exact size of the existing chamber and stuck in in the drill chuck and used it to align the pointer to the chamber. Move the table around till the pointer went in the chamber without resistance. Then I knew the collet with the end mill put back in was aligned properly.
Then I just aligned each chamber with the pointer and then re-installed the end mill ( since that would be .003" larger than the groove diameter in the barrel) . By the way...….I slugged the barrel with a lead ball and obturated it and drove it out of the barrel and.....then learned how to measure a seven groove barrel rifling with a caliper to get the exact diameter of the groove to groove in the barrel. The danged barrel grooves were something like .385"s and the chambers were about .372"s. As far as I remember.
Re-install the end mill after aligning the chamber and mill the chamber hole to the size I wanted. Do all six of them naturally.
Then I had nice smooth chambers all silver and shining and now....the right danged size for the barrel groove diameter. It was cool.
Before the proper sizing of the chambers my Navy shot well when it felt like it and not well when it felt like it. Drove me up a wall. I'm surprised I didn't go explore that trauma in therapy.
Anywhoooo….after the chambers getting to be the new size at .003" larger than groove diameter that Navy became my sweetest prized possession AND my most accurate cap&baller.
I had a phone Pal fer a little while. He was known as the best gunsmith with Remington cap&ballers for the competition shooters there was. "Ball Accuracy" was the shop name. We'd talk shop at length at times and being the decent Hombre he was he listened to my method of enlarging chambers and gave me his method. He advised me about chucking reamers since I guess he was a machinist of some sort. Chucking reamers that could be had in increments of .001's inch.
That's all she wrote. It was chucking reamers for me ever since because I could get so many different sizes.
I finally had Starrett take an edge finder they sell and enlarge the cone on one end so it was a half inch to start and shaped small to the end. I have a blue print of the tool. Anywhooooo the cone end goes into the chamber snug with the cylinder in the vise and I move the table around till the edge finder modified tool tells me it's perfectly aligned with the chamber so the chucking reamer put in is perfectly aligned also. Cost me over $400.
The edge finders have three parts all the exact diameter with a spring inside holding them together. The longest part in the middle and the shorter flat ended part on one end of the body and the cone shape on the other. I put the tool in a half inch collet since the tool is a precise half inch diameter exactly. (the flat ended part on the body of the tool goes into the collet and does nothing). Then the collet with the tool cone end down goes in the spindle of the milling machine to line things up.
When I move the table around and the precision parts of the tool line up perfectly then the spindle where the chucking reamer is in it's collet it is perfectly lined up with the chamber. Edge finders can come making a click when the edge is found or light up when the edge is found or when the tool parts all align perfectly. I don't find edges with it but find the center of an existing hole as in chamber. My tool has no clicks or bells or lights or anything. I use my finger nail feeling for little edges between the tool parts till I feel no edge anywhere. That means the tool parts are aligned perfectly so the tool is at the exact center of the hole.
I began to promote the idea that chambers close or even a little over the size of the barrels groove diameter would give pretty danged good consistent accuracy in cap&baller revolvers. I tested it a good deal in my own cap&ballers so I knew it was a good deal.
I have to say.....if the ball or bullet made of lead is .001"-.003"s over the barrels groove diameter, in my humble opinion, it will shoot better than if the chamber is smaller than the barrels groove diameter. The .003"s inch over groove diameter is pushing it some.
I had a Paterson Uberti revolver with something like .385"s barrel grooves and chambers at something like .372. It just would not shoot well. I reamed the chambers to something like .386"s and it transformed that danged thing fer the better. Real transformation to a real accurate Paterson. Pop cans with holes in them at 40 yards and such with that gun. Of course I use a .395 ball in it. That technically makes it a 40cal. right?
I'd have to mention that I seldom reamed the chambers all the way to the bottom of the chambers. I'd ream down into the chamber about as far as the ball would ever have to go into the chamber on the powder. Never ever went too thin under where the cylinder notches are. Always stay above those in the chamber.
Anywhoooo...people would relate to me that they didn't have a milling machine or the moola to pay a gunsmith to ream chambers. They would tell me they got those adjustable hand reamers to do the reaming. Some people used drill bits on their drill press.
Anywhoooo….the reaming always worked fer me but......it's merely an opinion of a "Bonified Kitchen Table Gunsmith" and not written in stone by Moses or some Belgian advanced gunsmith.
Of course there's Uberti guns like the Pocket Police that comes with 36cal. chambers the same size as the barrel grooves. The distressed finish Pietta Army Colts have matching chambers and barrel grooves according to the Dixie Cataloge I think. The Italian Pedersoli target revolvers like the Rodgers and Spencer and the Remington 1858 revolvers have matching chambers and barrel grooves pretty close. My Pietta target type Remington has matching , .456's barrel grooves and chambers.
The Pietta Navy and Army with the patina finish in 44cal. have rifling .003's deep and chambers .446 and grooves at .446's. The shallow grooved rifling seems to be reserved for the target guns like the Pedersoli and the Pietta Deluxe Remington and the Patinia and others. A Pedersoli Remington costs a few dollars more than other standard ones.
When gunsmiths put Badger barrels on Remingtons they had matching chambers and barrel grooves if I'm not mistaken.
Anywhooooo....I used my dial indicater gauge to gauge the straightness of the chucking reamers in the 5/16ths collet stuck into the machines spindle. It showed the chucking reamers were something like .006's inch out of true. Since all the reamers new and old didt he same thing with the 5/16ths collet and not the 3/8ths collet that showed no movement of the arrow on the dial gauge at all I asertained that.....the danged (*&$%^#__)$%^ 5/16th's collet is bad.
That I figure at this point is why the" first reamer" I used to do the cylinder I have in the machine that was 3/8's collet worked like it should and then going to the 5/16th's collet fer the 5/16's shank reamers would not do the job. Freakin bad collet. I can look at that collet and not see anything wrong with it. Collets are thick and strong and pretty much life time users. A bad one seems not possible but......in my world weird things are always happening. Lady Luck with her fickle finger of fate shoves it "in the wrong place" with me all the time.
If anyone reads this.....hope it doesn't drive ya nuts.