Oversized Revolver Chambers

[nkbj]

In swapping around revolvers I've become the proud owner of what's probably a really nifty paper weight, a Pietta 1858 cylinder that somebody messed up with oversized chambers from a bungled reaming to larger diameter. I could put some round ball in it and see how it does. Just haven't bothered to tell the truth of the matter. A .454 diameter bullet just falls right in! The dial calipers are showing egging as big as .457. Reckon I could try the .465 ball mold but might spring a loading lever.

And that got me to wondering...
So what's the biggest increase over groove diameter any of you fellas have in your pieces?

 

[Treestalker]

Hi!, I don't know but that's a good question, in light of the fact that some claim chain fires occur at the rear of the cylinder; If reaming a cylinder for a better ball/throat/bore fit compromises the safety of the cylinder, is it worth doing? On the other hand I have first hand experience with a brass framed .36 G&G a friend owned that we had fired a lot with lubed chambers and no problems. One day, we were producing an oil well at a remote location and my friend brought out his piece and said, 'damn it, I left my Crisco at home'. We thought what the hell, balls were tight, just like always; same load, same balls, same caps. No lube. Three chambers chain fired, my friend, new to black powder but an accomplished pistolero, almost dropped the gun and spoke some of the most outstanding Spanish profanity I've ever heard. Sure enough, I tried a shot with the remaining 3 loaded chambers and got 2 shots for one trigger pull. Later back home we loaded and fired several cylinders loaded the same way but topped off with Crisco and Bore Butter and no problems. Same load, same balls, same caps. I have never failed to lube my chamber mouths since, except when using the new (then) commercial wads for revolvers. I have never had a chain fire since. I don't know about the ill fitting cap theory; I've fired countless loads with caps I had to squeeze to fit on the nipples, theoretically making a larger gap on part of the cap/nipple interface, with several different types of C&B revolvers and never had chain fire. Perhaps a close study should be made of this phenomenon. I am convinced that with my friend's revolver lube made the difference.

 

[sussexmuzllodr]

shoot .454 in my uberti. never used lube. no chain fires.

 

[nkbj]

Heh, maybe those oversized chambers would act like one of those screw barrel pocket guns from the early 1800's.

 

[nkbj]

Oh my gosh have I started another flash over argument thread?
They remind me of the Alamo re-enactors' opposing sides that started yelling back and forth "GREAT TASTE" and then "LESS FILLING" until they emptied their blanks at each other.

 

[Scota@4570]

The chamber walls are now to thin for safery's sake. Remington's have thin chamber walls to start with. Get a new cylinder.

I reamed mine to .001" over groove diameter, accuracy became excellent.

 

[bang]

A bit of team is one thing but that is excessive. .001-.002 over groove max will improve accuracy should the cylinder bore be under.

 

[SDSmlf]

So what's the biggest increase over groove diameter any of you fellas have in your pieces?

I have found best accuracy with the cylinder chamber diameter .001”/.002” larger than the barrels groove diameter. 45 caliber Piettas barrels seem to have .450” groove diameters (.438” bore with .006” deep grooves), with cylinder chambers around .444” diameter from the factory. I like to open the chambers up to .451”/.452” diameter for best accuracy, at least this my opinion.

Uberti 45 calibers are a little different size wise. Barrel groove diameters run around .458” (rifling is .0095” deep) and their cylinder chambers .4495”/.4500” diameter.

A .454 diameter bullet just falls right in! The dial calipers are showing egging as big as .457.

It’s possible someone opened the chambers in your gun to a diameter appropriate for an Uberti bore size? Have you checked the bore and groove size in your gun?

 

[rodwha]

I got my Pietta NMA Sheriff in 2013. I thought it would have the slow 1:30” twist. It did not. It has a 1:16” twist. I also slugged the bore. Mine is a hair over .452”.



And the lands:



I had never slugged my chambers but assumed them to be .446” as I read it common. Another fellow reamed my chambers to .449” and chamfered them, and I honestly can’t say I can tell a difference at 15 yds offhand. I’ve been wanting to ream them to at least .452, and really .453”, but have been hesitant.

I’ve read often enough that accuracy comes with chambers .001” over bore, and we see lead bullets always .001” over bore. Has anyone brought theirs to bore or .001” under and found obturation made the slight difference negligible? Those thins walls give me pause, though I’ve spoken with a couple of people who claim to have do so AND use energetic powders, heavier charges, and bullets much like I am. Were I using standard Goex I wouldn’t be concerned with going to .453-4” using a ball or small bullet.

For a while I tried shooting bare ball with no felt wad. Worked just fine (T7 though) and never had a chainfire. However my father came down and we went shooting BP together and his ASM 1860 chainfired despite him using a felt wad.

 

[Bad Karma]

I have four Uberti Colts and three Second Gen Colts all with .456” chambers. They all shoot passably well, and a couple of them will shoot full power loads under 1-1/2” at 25 yards. Pietta “shooters“ model revolver has .456 chambers from the factory and the external dimensions were functionally identical to the standard cabelas pietta.

 

[Smokey Plainsman]

Sounds as though Junior got into the Dremel tool box again.

 

[Sven205]

I have a shooters model Pietta and an Uberti NMA that both use a .461 ball mold.

A .457 doesn't shave a good enough ring for me on either.

 

[SDSmlf]

I have a shooters model Pietta and an Uberti NMA that both use a .461 ball mold.

A .457 doesn't shave a good enough ring for me on either.

That’s a larger cylinder bore diameter than I have found on unmolested Ubertis, and about correct in my opinion for their .458” barrel groove diameter.
Have not had the opportunity to measure a Pietta Shooters Model, but a diameter greater than .457” would more than fill the .450” groove diameter i have measured on the standard Pietta NMA, at least in my opinion.

 

[Newtire]

There used to be a guy who reamed out cylinders but don't see him on the net anymore. Is there a service anyone knows where one could get this done?

 

[arcticap]

There used to be a guy who reamed out cylinders but don't see him on the net anymore. Is there a service anyone knows where one could get this done?

Charlie Hahn does this among others. --->>> Hahn Machine Works
Post if you need more leads.

That’s a larger cylinder bore diameter than I have found on unmolested Ubertis, and about correct in my opinion for their .458” barrel groove diameter.
Have not had the opportunity to measure a Pietta Shooters Model, but a diameter greater than .457” would more than fill the .450” groove diameter i have measured on the standard Pietta NMA, at least in my opinion.

The Dixie product page for the Pietta Shooter's Model recommends a .457 ball, but a user review states that he needed to use a .464 ball to get good results with his.
I believe that Pietta uses a special barrel for that model which is not a standard barrel. --->>>

https://www.dixiegunworks.com/index...21/product_name/RH0135+Pietta+Remington+Army+

 

[SDSmlf]

The Dixie product page for the Pietta Shooter's Model recommends a .457 ball, but a user review states that he needed to use a .464 ball to get good results with his.
I believe that Pietta uses a special barrel for that model which is not a standard barrel. --->>>

Shooters Model has a progressive rifled barrel, no doubt not their standard NMA barrel. I was curious as to what the bore and groove diameters in the barrel were. I have measured the standard model’s bore at .438” diameter with a groove diameter of .450”. Sounds as if the Shooters Model has a larger groove diameter and possibly a larger bore.

 

[Bad Karma]

There used to be a guy who reamed out cylinders but don't see him on the net anymore. Is there a service anyone knows where one could get this done?

John Taylor does this too. Taylor Machine in Puyallup WA...

 

[arcticap]

I was curious as to what the bore and groove diameters in the barrel were. I have measured the standard model’s bore at .438” diameter with a groove diameter of .450”. Sounds as if the Shooters Model has a larger groove diameter and possibly a larger bore.

The Shooters Models have been made in batches over many years which could mean that the bores are not all the same.
FWIW it's been posted that Dixie used to sell a Shooters Model that didn't have the progressive rifling.
Also, I found this posted by oldelm about one that he purchased:
" I slugged the barrel and it has .456-57 grooves, the chambers measure .457. The bluing is a superb dark blue. It has "BS" date stamp,..made in 2002. "
Navy Arms also sold their version of the Pietta Shooters Model from 1980 to 1995 that had progressive rifling.
Someone with a 2017 Shooters Model posted that his cylinder had 2 indentation marks on it that may indicate hardness testing, or at least to differentiate that it's different than a standard one.
It was speculated that since it will fit in standard models that it may possibly be made from stronger steel due to the larger chambers that he said needs .460.
Bob Hatfield posted that the lands are wider:
" The barrel's rifling is opposite twist from Uberti's and regular Pietta Remingtons and the lands are wider and of course the twist is a gain twist. The top of the barrel has the old timey Remington address and all of the Pietta markings are under the bottom of the barrel. " --->>> Pietta NM Remington 'Shooter's Model'

There's a youtube video that takes a tour of the Pietta factory with the owner, which discussed a special older style rifling machine that was used for making special barrels that took extra time to make. It immediately occurred to me that it might be used to make barrels for the Shooters Models.

 

[Newtire]

Thanks you guys. I believe I will get this done on a revolver or two.

 

[rodwha]

Shooters Model has a progressive rifled barrel, no doubt not their standard NMA barrel. I was curious as to what the bore and groove diameters in the barrel were. I have measured the standard model’s bore at .438” diameter with a groove diameter of .450”. Sounds as if the Shooters Model has a larger groove diameter and possibly a larger bore.

What year is yours? Mine is a 2013 Sheriff’s model, and I slugged mine and found it to be .4525” X .442” and with a 1:16” twist (really thought it would comein 1:30”).