Groove Diameters Larger than Chamber Diameters?

[ClemBert]

Let me run this by y'all "experts".

So, in order to efficiently utilize the gases developed from burning BP it would seem that in order to obturate a bore opening thus preventing the escape/loss of useful gases you'd want a projectile to be larger than the bore. Specifically, the groove diameter. This obturation could occur by either an expansion of a projectile under force or by having the projectile larger than the groove diameter then swagging down as it enters the bore. I have seen specs that show revolver chambers as being 0.002 to 0.003 larger than the groove diameter. Thus, the conditions are in place for obturation. However, I have seen specs that show the opposite of this. In other words, it would seem that some revolvers have chambers smaller than the groove diameter (but as expected larger than the lands diameter).

My questions:

1. Are there certain manufacturers who have propensity to make firearms with chambers smaller than the groove diameter?
2. Are there certain models that commonly have chambers with smaller diameters than the groove diameter?
3. Do you own any of these?...and have you considered having the chambers increased to 0.002 larger than the groove diameter?
4. Does expansion of the projectile occur to effectively obturate the bore opening?

 

[Pops]

My answers:

1. Pietta definately does..can't speak to other brands.
2. All 6 of my Pietta models chambers are smaller than the G to G..
3. See #2 .. I have reamed all my chambers to .001 larger than bore diameter.
4. Yes.

I just recently did the reaming, and only test fired the '58 Remmie...
Unfortunately the front sight was missing when I got it, so, the accuracy test will come later.

PS.. I ain't no expert.

 

[[email protected]]

The guy who built mine does it for a living. He can make the chambers or
barrel any size he wants to. My .36 cal the chambers are .357 dia. The
groove dia. of the barrel is .355 I use a .360 ball. So the ball is .002 larger
than the groove dia. of the barrel. I know another guy who does the same
kind of work and he told me when I bought a Ruger, to make sure the chamber was .002 larger than the groove dia. So they both agree. By the way
the guy who told me about the Ruger has won the National Pistol Championship the last four years in a row. They must know something.

 

[Oyeboten]

Hi [email protected],


Who is the guy?


I might like to have this done to one of mine...

 

[mykeal]

1. Not sure about the tendencies of any manufacturers in this regard. Here's how mine stack up:
3 Rugers - all have chambers 0.001" over g2g diameter
7 Ubertis - 4 have chambers 0.006" to 0.001" over, one is the same and two are undersize, 0.004" and 0.010".
4 Piettas - two have chambers over (0.003" & 0.001") and two are undersize (0.002" & 0.005")
3 Euroarms - one has chambers 0.002" over, two are undersize (0.003" & 0.001")
1 Colt Blackpowder Arms - 0.001" oversize
Have not measured my two FAUL 1850 Armies.

2. I see no correlation with model design in my samples, except perhaps for the Ruger Old Armies.

3. See the answer to 1. above. I've considered it, but as poorly as I shoot it's down a ways on the list of priorities. I have other things to do first to improve my accuracy. Like practice more.

4. In my opinion, yes.

 

[AbitNutz]

There is nothing better looking than a pistol with an unfluted cylinder and an octagon barrel. As a true an absolutely dedicated ROA owner and fan that is difficult to admit.

Thanks for the photo...

 

[ClemBert]

You don't have to admit anything!

 

[AbitNutz]

I wish people would quit posting that particular photo. That's very likely to cost me a year of waiting for Clement to finish and $1,500 odd dollars of wallet lightening.

 

[ClemBert]

Thanks for the input and the measurements fellas. One of these days I need to slug them all out myself.

 

[scrat]

 

[Oyeboten]

Well...been groovin' here...


Uberti, Model 1858 Remington, Stainless Steel Model -

Cylinder Bores, all: .445

Diameter between Barrel Grooves: .462




Uberti, Model 1860 Colt, Civillian version, Blue -

Cylinder Bores, all: .444

Barrel: .453





SM ( San Marco ) 3rd Model Colt Dragoon -

Cylinder Bores, all: .446

Barrel: .460

 

[rifle]

I've been a proponent of sizing the chambers to match the groove diameter or...be .001 or .002 or .003 over the groove diameter of the barrel of cap&ballers for many years.
I've reamed chambers for quite a few other folks besides most all my own cap&ballers. I had Starrett make me a tool to center well enough on the existing holes of the chambers to ream them without changing the position of them.
Never had a complaint unless.....the correct size chambers meant not being able to get retail lead balls like Hornady or Speer. I have some Walkers that need .464 chambers and I use a .472 ball. Odd size. Some 36's end up needing the .380 or the .385 or the .390 and even the .395 balls.
That means in certain cases the casting of balls with bought moulds(if they exist) is imperative. The chambers can be within a certain spec. size to help the "ball size" thing. You can work in a spec. in chamber size anywhere from having the balls sized by the chambers to equal the barrels groove diameter or go to .001 over or .002 in. over or .003 .in over. I've gone as much as .006 in. over the groove diameter in a coupla my guns.
It depends on the gun and what you want from it. A coupla my Navy Colts had grooves measured at .383 and .385 and I reamed them both with a .388 chucking reamer. Four flute,straight flute chucking reams. They come in sizes .001 and even sometimes .0005 steps. Like get a .454 or a .4545 reamer. Mostly they come in steps of .001 inch.
There's my old ground hog killin Walker with chambers at something like .467 to size for the .464 barrel grooves(hard to remember all the sizes of my guns chambers). That Walker has taken out ground hogs digging holes in the farm fields at out over two hundred yards at times. Lots of 70 to 100 yards kill shots on them hole diggin little fat critters. Gotta help feed the buzzards ya know. ha ha ha
I reamed almost all of the cap&ballers so I have to measure the chambers to get the right balls to go shooting ha ha ha I have something like 25-30+ cap&ballers revolvers ha ha ha Can't remember all of them. I find them in my underwear draws and under the bed and under stuff in the closets. ect.ect. Like finding new guns since I forget how many I have.)
Anyway reaming the chambers makes them shoot better.
The target grade cap&ballers and the Special Pietta guns have chambers equalling the barrels grooves most of the time.
Anyway I use the .472 mould I got Lee to make me for some Walkers. Cost a hundred dollars set up fee every time I order four at a time since I've sold Walkers that are reamed and the mould goes with them. The odd size chambers are a tricky situation at times.
The titanium ball Lee used to swag the finish size to the Lee moulds I get at .472 size cost me a hundred dollars right off the bat. One time. They make me buy the titanium ball but they keep it.
Anyway sometimes there isn't a mould made to fit the needs of reaming some guns chambers. You need to find a mould maker that does "balls" moulds sometimes.
Anyway you can,or I have done, reaming of chambers as much as .006 over the groove diameter to test them out.
You have to take note of how thin you might make the chambers walls from reaming. Actually there's not much need to go over .003 in. larger chambers compared to grooves in the barrels. Equal size chambers to barrel grooves is good enough for cap&ballers.
You would never go lead bullets over .003 in. in a cartridge revolver that shoots lead conicals. Conicals are another story as is smokeless powder. The rule of thumb for smokeless powder cartridge guns is the "lead" conical bullets go to .003 over groove diameter in the barrel rarely and mostly .001 or .002 in. over the groove diameter of the barrels and....the chamber throats need to be the right size for them over sized bullets. Pressures rise when the projectiles seal the bores and have to do some swagging to get into the barrels grooves. That goes for cap&ballers too.
The pressure rises when the chambers are reamed to equal or exceed the groove diameter of the barrels. That's why I tell some to watch carefully using Hodgdon 777 powder that is hot like a smokeless type powder. High energy powder...that's 777.
Anyway there's a difference in the sound of a gun shooting reamed chambers compared to the barrel grooves. The sound a lot of times gets higher pitched. A crack like a muzzleloader rifle breaking the sound barrier.
Anyway......The guns seem to always get more consistant accuracy with the chambers reamed to equal or exceed by .001 in. or a few .001's the grooves diameter.
When you consider the fouling by blackpowder the Italian guns,I've found, are reamed under sized in the chambers to accomodate successive shots fired and fouling building.
I asked Val Forget about that once. Anyway the release of some of the pressure with an under sized chamber is a liability thing too I'd guess.
If you aren't going to accomodate the guns barrel with a system that keeps the barrel and chambers clean of blackpowder fouling you're better served to leave the chambers under sized.
The grooves get fouled with hard blackpowder fouling making the barrel diameter inside smaller ,and that goes for the chambers too, if you don't clean the barrel and chambers regularly with a damp patch on a jag on a rod. Like every cylinder full fired.
I use "lube pills on the powder and under the balls" where they do some good and can do their work properly and keep fouling to a real minimum. Some people use wool wads saturated with wax/lube mix under the balls. The wax/lube has to be stiff for the lube to work when "on the powder under the balls".
I can shoot a coupla hundred balls from a Colt revolver and never need to clean the barrel or the chambers(hard fouling builds in the chambers and progressively makes them smaller) or lube the arbor to keep the cylinder turning when using "lube pills". The mix of 50/50 wax to lube is good for cold weather and the mix of 2/3'rds wax to 1/3rd lube works in hot weather. You have to be able to carry and handle the lube pills and don't want the pills so soft they get squished into the powder. I had that happen in hot weather once or twice when my lube pills were too soft from the heat. I had to stop using the pills since I didn't make any stiffer onesd with more wax yet and was using "cool weather" lube pills that the heat made too soft. I went to the patch and rod to clean after every cylinder fired. The accuracy improved. Soft pills can make the sound of the chamber firing muffled like all the powder isn't igniting. When the pills are right the sound is sharper and the accuracy is better.
Pietta can have under sized chambers anywhere from,on average, .003-.006 inch out of the box. They seem to be fairly consistant in accuracy like that though . I don't believe the lead balls obtuate as much as most people imagine but the Piettas are chambered good enough to be good shooters out of the box.
The Uberti's used to be more undersized in the chambers than Pietta is now. Newer made Uberti's.....I don't know how they are chambered now. I haven't checked any new Uberti ones out lately.
I bought a new barrel from VTI(most likely or Taylors) that measured .366 in. in the grooves and I ended up with a new Uberti cylinder that measured .369 in. in the chambers. I was collecting parts to fix peoples cap&ballers and ended up with extra parts. Anyway the new parts went on my old Uberti Navy Colt. It shoots as accurate as any 38cal. revolver,within it's range, or any revolver I've ever shot. Multiple rabbits have gone in the freezer with the help of that Navy Colt. ha ha ha The chambers being .003 in. oversized for the barrels grooves makes it "a shooter".
Anyway the Pietta distressed finished Colts and Remingtons have chambers that match the grooves in the barrels. Look in a Dixie Gun Works catalog and you'll see the specs. Everyone needs a Dixie catalog. There is a wealth of info in there from Turner Kirkland the founder of Dixies.
Anyway the metal of the "distressed finish models" Pietta's has been hardened so they don't rust too easily. Maybe that's why they size the chambers the way they do being equal to the barrel grooves. Hardened metal.
The rifling grooves are shallow at .003 in deep too in those Piettas distressed finished revolvers. Good for sealing the grooves of the barrels. Barrels with grooves too deep are harder to get to shoot really well I've noticed.
Another Pietta with chambers matching the barrels grooves is the "Shooters" Remington sometimes referred to as the "Tiro" for some dang reason.
There are some Euroarms Rodgers and Spencers with chambers that match the barrels grooves.
The Pedersoli Rodgers and Spencer has chambers.001 smaller than the barrels grooves.The Remington Pedersoli sells has chambers over the groove diameter (I think I remember that right) of the barrel.
The Belgian Colts Centennials 1860 Army by Centaure Company has chambers always close to .445 and barrel grooves to match that.
The regular type Italian guns are almost always with chambers under sized for the barrels grooves.
I have a Pietta 1860 Army from Cabelas that has chambers I reamed to be at least .003 inch over the groove diameter of the barrel. It shoots 3/4 inch groups at 20 yards off the bench. Sometimes off the duelist one handed shooting. Sometimes. ha ha ha
Anyway if the chambers are thick enough to be reamed it seems to work out for the best but....I'd recommend that standard loads be used like 25-28gr. FFFg in the 44's and 20-23 gr. FFFg in the 36's. The standard loads are plenty good.
It all depends on what you want out of your cap&baller. They are meant to be close range combat weapons and that doesn't mean Olympian target shooting. Minute of "bean can" at 15-20 paces is plenty good for a shooting session with a cap&baller.My friend the illustrious "Smoking Gun" is a bean can specialist. ha ha ha
That's what they were meant to be. The cap&ballers. The Army expected the guns,I've read,to be used at from 17 to 28 feet in close range combat. That isn't saying they were meant to be target grade guns. Bean can shooters at close range.
So....if you can only get good shooting at close ranges like that with your cap&baller you aren't really a minority. If you can hit or get close to a target the size of a big grapefruit at 20 yards that's good enough to have fun shootin. Don't get carried away with the attempted accuracy with the cap&ballers. Just see what your gun can do and figure the gun is a close rsange combat weapon to shoot people sized targets. Don't ruin your fun trying too hard with a cap&baller.
If you enter the world of "target shooting" cap&ballers get used to the idea you may have to become a "Kitchen Table Gunsmith" to accomplish that. Not always anymore considering the way the new CNC machines help the manufactures make the guns with good specs tolerances.
In the old days most people would tell you that,"you can't hit the broad side of a barn with those cap&ball revolvers". Some people I talked to in the good old days would remark how their old brass framer Colt could hit Coke bottles at 70 paces. They were the lucky ones and got a "one in a million" accurate cap&baller. Today we are almost all lucky in the fact we can easily get a cap&baller that shoots well enough right out of the box.....if you don't have expectations that are too high.
Some cap&ballers are used for competition and are made to be accurate.The barrels have to be prime for that and the Italian barrels aren't always up to that type work. If you are going to ream chambers for accuracy then make sure the barrel is right for that or forget the reaming of the chambers.
Barrels can have tight spots or loose spots. The worst loose spot is at the muzzle end of the barrels. Tight spots swag the balls small for the barrels from that point on.
You can check by bumping up lead slugs in different places in the barrels and measuring. All the tight spots can be found but not the loose spots too easily unless they are at an end of the barrel. The lead slugs going all the way thru to measure just give the smallest groove diameter. Measuring them takes some finesse to do properly. Thank God the barrels aren't five grooved.
Most people seem to measure improperly when checking the barrels to determine the size of the grooves diameters . Thank God the "balls" give a good margin of error when they are being sized in the chambers for the barrels.
Conical bullets have a good deal more surface area to cause friction and raise pressures. FFFg powder in cartridges for pistols can be very erratic and raise pressures as much as 50% or more with the comparing to same volume of FFg. Not in any predictable pattern either as the loading books can show.
Using FFFg powder in cap&ballers can have a good presure when the chambers are reamed. The balls being much easier swagged into the barrels(my therory anyway) being flattened by swagging into the chambers around their circumference only helps matters as the surface area to cause friction is rather small. The balls end up in the chambers and are sized to be like a round nose short bullet with the round nose on the base also. The larger the ball is compared to the chambers the widder the circumference flattened to make the driving band around the ball. That note can make a chance to get some cantankerous guns to shoot better.
Anyway I've found that at least in my tests that to get the most from yer cap&baller you make sure the barrel is proper and needs no lapping and ream the chambers to be at least equal to the barrels groove diameters. Just my opinion. Just my opinion of course.
Anyway you have to have a good measurement of the barrels grooves. The calipers seem to always give an under sized reading trying to measure barrels. The lead slug needs to be put thru the barrel and then very carefully measure that to get the groove diameter. It's tricky too and you need to develope the knack for it. It is tricky.
You can squish the little fragil edge of a land sticking out of the lead slug with the slightest pressure of the calipers. The widest measurement comes from getting on a land edge on one side of the slug and a land edge on the other side most of the time. One important thing. The lead slug must be obtuated or bumped up inside the barrel to get the actual size and then pushed thru with a rod. A rod on each side of the lead slug in the barrel and one on a solid surface and the other sticking out the barrel so it can be hammered to bumb up the slug in the barrel is the only proper way to measure the inside of the barrel to get the groove diameter.
Anyway hope this helps all you "Kitchen Table Gunsmiths" out there. The only reason I take time to type this stuff is to try to be a help to all the other "cap&baller aficionados" out there. I'm a Saint ain't I? ha ha ha Saint Rifle. ha ha ha ha ha ha

 

[Old Fuff]

Not only are bore diameters often oversized in C&B revolvers, matters get worse when someone spends $200 or so for a metallic cartridge cylinder and finds out what happens when you shoot a .358" bullet down a .380" bore.

Or whatever... :banghead:

 

[arcticap]

I noticed that "Saint" rifle didn't mention anything about reaming ROA chambers. Maybe they're made to be just perfect from the factory as if they're actually made by the real Saints Sturm & Ruger!
Oh when those Saints, come marching in.... ha ha ha ha ha ha ha ha

 

[mykeal]

I don't know if it's intentional or not but all 3 of my ROA's have all 6 chambers 0.001" larger than the groove to groove diameter of the barrels.

 

[Old Fuff]

No, it was intentional - and most ROA's are correct in this respect. They also work fine with cartridge cylinders chambered in .45 Colt.

I think that undersized chambers on "regular" Italian-made cap & ball revolvers weren't an accident either, because the high-priced ones made for match shooters are usually dead on for this highly demanding market.

 

[Oyeboten]

Very glad to be getting informed about all this.


I sure love my Cap and Ball Revolvers, and, I will elect one to be a Candidate then, for some of these procedures.

I will test it well before doing anything, then, test it well after, and see what the difference is.

 

[Hellgate]

Oyeboten,
Be sure to have a decent vise or means of aligning the reamer to the chambers. I ruined a couple 3 cylinders because the vise I had for my drill press was substandard and I got off axis even though I was turning the reamer by hand with it mounted in the chuck. I did about 6 cylinders and screwed up 3. An expensive accuracy job. The replacement cylinders were left as is from the factory. I have two identical 44 "Navies" and they have different recoils since one is reamed and the other got a new cylinder. The reamed one kicks more if memory serves.

 

[Oyeboten]

Hi Hellgate,



Makes sense...thanks you for the word of caution on that.


I have some Machine and Metal working capacity here, but not a lot, and mostly fairly primitive.

Have a good old Drill Press with a stout Table which allows bolting down a fixture, and some fine Starret Squares for checking set ups...a few good Vices...Verneer Dial Callipers...I dunno...maybe I could do it.


All in all, making sure the Barrel is not constricted at the Frame...correcting that, if it is...by one means or another.

Making the Cylinder Chambers a right size to be over-size to the concluded Bore...


Seeing to it the Forcing Cone is well shaped...


These would be wonderful skills to have...even if the Tooling/Reamers may tend to vary from one project to the next.


It would not bother me one bit if I ended up with a .465 Bore or something...sounds like fun actually.


Tapering/Chamfering the concluded Cylinder Chambers...etc.

I'd be into it...just want to make sure I have a good handle on what I am doing.

No convenient way for me to Line-Bore tidy-up the Cylinder Chambers actual align to the Barrel though...that'd have to be jobbed out I think if I wanted that feature to be ideal.

Darn...too bad I did not elect to be a Machine Shop operative years ago, when I got into Wood Working ( instead ) ...

Pout...


Lol...


If one has a Bullet Sizer, one can always get or modify a Sizing Die for making any Balls or Boolits to the diameter one wants for a particular Revolver...so, worrys on the expense or difficulty of getting odd-size Molds should not be an issue, when Store Bought or self Cast Projectiles can be easily re-sized as one likes.

 

[rifle]

Sorry I forgot the Ruger Old Army when trying to remember guns with decent chambers. Probably forgot because I just figure it's expected for Ruger to do things well.
Old Fluff, don't dispair if you got the cartridge cylinder to shoot 38's out of your cap&baller with the .380 bore. I hope you mean .380 grooves since some call it bore.
You can ream the throats out of the front of the chambers to .380 . If the chambers aren't .380 where the cases fit you can make them .380. Just ream or drill the chambers straight thru at .380 and use a "heeled" bullet that can fit the barrel. Might need to get a mould madeto cast yer own.
Your rev would be more authentic that way shootin heeled bullets.
With the mention of making sure the reamer or drill is aligned properly when enlarging a chamber.....it would be a good idea to have things lined up well. That can get to be too much to mess with if you don't have a milling machine that is within a coupla .0001's.
There may be small enough adjustable reamers made that would work by hand. They woul follow the hole so to speak.
If you had a gunsmith do the reaming you ave to be careful and ask how they do it. I think there would be some that would "just eyeball it". You know...because it's just a cap&baller. You'd want assurance the person would actually indicate it off the hole "as they say". If they say that ask them exactly how they do it. Some know that could be a way to do it but never really ever did it and never actually will.
Years ago I had a professional gunsmith actually say that and put strange punch marks on the front of my cylinder. Deep too. Then proceed to ruin my cylinder. He bought me a new one. Had to keep the old one though....just in case I might find a use for it. He said he'd keep it as a paper weight. He actaully figured that if he got me a new one since he ruined my original one that the original one was his. Some strange rational.
Anyway...gunsmiths and machinists can drill holes where they go. Not all of them can center up on an existing hole.
Some people indicate off the edge of the hole by finding the widest point on one x or y axis. Then go so many .001's to what the center would be accounting for the width of the indicator tip. The move on the other axis and find the widest point and go so many .001's to what the center should be. Do that over and over and every time you're supposed to get better centered. Some machinists say they go three times and then figure that's centered enough and drill or ream. You need a milling table for that and you can get them for a drill press but then it still needs set proper perpendicular to the chuck and all.
I think an adjustable hand reamer is about the cheapest best way to get it proper enough.
The best cheap way is to have Manson or Clymer make a piloted reamer for you. Of course the dang tapered chambers the guns have so often would foul that plan.
I guess a gunsmith that's reasonable is the best bet if...they will do it right.
I guess that the best way is to buy a gun with the chambers already the right diameter for the barrel.
A cap&baller can still shoot real well with .003-.004 in. undersized chambers.
I think that using "lube pills" that are solid enough help seal the grooves and help stop blow by of the gases. You know....2/3rd's wax to 1/3rd lube is about right. The wax/lube doesn't have to seal a long time. The wax/lube pill and the ball aren't in the barrel very long once the powder ignites.
I guess getting a mould made thats a very short stubby flat base round nose bullet would help. One that's the length that is the same as the width of a ball but with the flat base made a hollow base would cure the undersized chamber thing. The short stubby hollow based bullet would swell to seal the grooves. Short and stubby to imitate a ball swagged into a chamber. That would be like a short stubby bullet with the front and rear rounded. Flatten and holoow base the rear and that's a short stubby hollow based bullet real close to the shape and weight and length of a ball. Of course a sligh heel would need to be on the bullet too. That would be a short stubby hollow based heel bullet the length matching the width of a ball.
I e-mailed a guy that makes those moulds already. Actually a coupla people can make them I found out. Made with a lube groove too. NEI Hand Tools makes a bullet like that without the hollow base...in the .456 diameter section. They would hollow base that mould though. I asked them once and they said they would do it. The bullet is short and heeled so it goes in the chamber. Add the hollow base to it and that's a good bullet/ball to seal grooves and shoot well. Short hollow based heeled ballet. Sort of like the Buffalo Bullets Ballet but with a "real" hollow base and a lube groove.
A hollow based bullet mould needs to be a single cavity mould. Slow casting. Worth it if it shoots real good and yer chambers can be left undersized and no need to get them reamed. I think it would work well.

 

[Oyeboten]

Hi rifle,

I like those Bullet/Boolit mentions.


I have been thinking of dished base flat face Wad Cutters also for C & B...which would be fun, and nice for Paper or SD.

Now, the Uberti Remington I got the other day, the maximum diameter in the Barrel, seems to be .462 ( whether one calls this the Bore, or the Groove, since it has been called either one over time, of course.)

And, the Cylinder Chambers, once I got the right knack for measuring with the Verneer Dial Calliper, all are a uniform and tidy .445


Now, this seems like a disquieting difference to me.

I have not shot it yet, but I sure like the Revolver...so, probably it would be my Candidate for attending to some of these possible improvements.

No idea if the Barrel has any constrictions where it is in the Frame or not...though I could slug it, and see how the friction feels as the Slug is pushed through various times...and or from one end, or the other.

 

[mykeal]

Slug it, then measure the slug lands & grooves.

 

[rifle]

Some people already make moulds for what one person calls his "BB" which is described as a ball/bullet. ([email protected]) Heel for it getting in the chamber,lube groove,rest or front is over chamber diameter to stay put in the chamber. I asked him and he said ge could "hollow base" one.
That would help accomodate the undersized chamber problem by the front riding part way into the lands and the rear "bumping up" from the hollow base expanding from the gases to seal the grooves. I think it would work with the right powder charge and if the "skirt" for the hollow base isn't too thin and flares out larger in diameter than the front of the bullet.
Old West Moulds makes bullets moulds about that way too. I've talked to him about it too. He'd make a hollow based heel bullet mould.
Then there is NEI which will make different things. Their .456 bullet for cap&ball(the lighter one) could be hollow based also I'd guess.
Someone mentioned dies to make/reshape bullets/balls the right size for the chambers. Well.....Rapine Bullet Moulds makes a little inexpensive press to push balls or bullets thru their inexpensive size dies made for the little press. They would make any size sizing die you want at increments of .001 inch. Don't cost much either. I have some they made me to size conicals for my muzzleloader rifles with the fast twist shallow grooved barrels.
When I first started sizing chambers in my cap&ballers years and years ago(where does the time go?) I used end mills in my little mill machine. I used what I called "pointers" to center on the chamber. I'd stick a rod in the spindle and turn the machine on(a drill press can work too) and carefully file the rod and smooth it up ,polish to finish size) so it was a real close snug fit in my chambers. I'd leave the end with nice sharp edge and flat and perpendicular to the rod centerline. If that was done well the rod didn't start in the chamber unless it was perfectly centered on the chamber hole. There's a small problem with the opening of the chambers being the true size and going in too deep the pointer would hit the chambers taper. I just got the pointer in the first part of the hole to line up. Then take the pointer out of the spindle and change it to the end mill I wanted to use to size the chamber.
I think before that I'd take a straight wood or brass or steel rod and slit the end a fairly long slit (about a little longer than the chamber) down the center. If the slit was centered well enough I'd then slip sand paper in the slit and roll it around the rod and stick it in the chamber and turn it with a drill stuck in a vise. I'd hold the cylinder by hand and ream or sand paper the chambers and get them to the size I wanted measuring with calipers. Trial and error and checking the size a lot. That would work. Almost like making my own cheapy adjustable reamer. I'd adjust by how much sand paper I rolled around the rod with the slit. It worked well enough. I's start with 220 and finish with 320 or 400 grit paper. Wet/dry worked good so I could rinse both the cylinder and the paper with water. I'd dirty the kitchen sink up a bit. ha ha ha I'd use a variable speed drill and run it slow most of the job. I'd turn the cylinder and hold it for awhile then turn it again so I wasn't reaming always at one position. I figured if I turned the cylinder and hold it awhile then turn it and hold it and turn it and hold it ect.ect. then the rod on the drill and myself holding the cylinder it would still get reamed out evenly and not with a lopsided hole....get a round hole by moving the cylinder to different positions often while do a chamber.
I'd do the resizing on cylinders I knew that if worst came to worst I'd be able to get another cylinder. ha ha ha
If you leave some drill lines or sand paper lines in the chambers I found the balls grip in there better. Like a chamber too smooth isn't as good as a rough one for holding the balls in there. The plunger widens the ball into the chamber walls and into the little line grips.