Undersized chambers in revolvers???

[nkbj]

Yes. Wall thickness looks a bit thin at 0.449” as it is.

Picked up one of the Pietta target 1858's a while back that the chambers were reamed. The chamfering on the chamber mouths was poorly done resulting in raised rims of displaced metal just inside the mouths). With a magnifying glass and Forster case deburring tool, removed the raised metal last weekend. Taking wall thickness readings down in the chambers came up with .045" average.

The chambers are a whopping .453"-.455" diameter (variation seems to be my dial caliper poor measuring technique as much as anything else).

Reckon it probably didn't perform too shiny with the chambers the way they were. Will find out what it does now. I've got a .465 round ball mold somewhere. Maybe now it will be serious bean can killer.
And if if it comes apart, I have an extra Pietta cylinder somewhere in the toy box.

 

[rodwha]

Picked up one of the Pietta target 1858's a while back that the chambers were reamed. The chamfering on the chamber mouths was poorly done resulting in raised rims of displaced metal just inside the mouths). With a magnifying glass and Forster case deburring tool, removed the raised metal last weekend. Taking wall thickness readings down in the chambers came up with .045" average.

The chambers are a whopping .453"-.455" diameter (variation seems to be my dial caliper poor measuring technique as much as anything else).

Reckon it probably didn't perform too shiny with the chambers the way they were. Will find out what it does now. I've got a .465 round ball mold somewhere. Maybe now it will be serious bean can killer.
And if if it comes apart, I have an extra Pietta cylinder somewhere in the toy box.

Checked mine and found them to be about 0.048”.

I use (weighed) 33 grns of 3F Olde Eynsford powder and up to a 195 grn bullet. Been fine for years and with a lot of lead down range.

I’m contemplating modifying my design and adding a little more lead, which will only increase the pressures a bit more. Couple that with even thinner walls...

 

[nkbj]

Well, if yours are that thin I feel a little better!

 

[M. De Land]

Well, if yours are that thin I feel a little better!

I reamed my 1858 Pietta to .450 with no issues and got clean metal all the way around in each chamber. This is the one I made the reamer spud for that went through the barrel hole in the frame for lining things up perfectly. Probably not necessary but line boring is the very best way to get cylinder and barrel co-axial.

 

[hawkeye2]

Line boring is well worth the effort if you want a really accurate revolver.

 

[rodwha]

I reamed my 1858 Pietta to .450 with no issues and got clean metal all the way around in each chamber. This is the one I made the reamer spud for that went through the barrel hole in the frame for lining things up perfectly. Probably not necessary but line boring is the very best way to get cylinder and barrel co-axial.

Is this something a typical gunsmith would do?

My Pietta cylinder was sent out alone so this certainly wasn’t done. I’ve been ondered about alignment as I noticed one chamber seemed a bit off.

 

[arcticap]

Is this something a typical gunsmith would do?

My Pietta cylinder was sent out alone so this certainly wasn’t done. I’ve been ondered about alignment as I noticed one chamber seemed a bit off.

I've read that there's another part to accurizing a revolver after reaming the chambers which involves altering the forcing cone.
Perhaps not always necessary but advantageous, especially in some instances.

 

[bigted]

Well ... for those of us that would like to shoot head shots on small game, the better the accuracy, the better success in the stew pot.

This requires a revolver to at least have the ability to shoot into 2 inch at 25 yds. Sound IMPOSIBLE? No i don't accept that either. No reason to not expect 2 inch general groups at 25 yards. If i am gifted to have the ability to shoot RESTED 2 inch 25 yard groups ... which I am ... then i will not rest till I have a percussion revolver that has the same ability. My Colt 2nd gen unmentionable revolver will do this so I will keep fiddling till i get my favorite style revolvers to do the same.

As for the question, I can only spin what makes sense to me, I do believe that an undersized soft lead ball or bullet WILL rob velocity more so that a properly matched ball/bullet to the groove diameter. Also, if per chance the smaller diameter is poured from harder alloy, I think all that bumping excercise robbing oomf from the rear will further loose power from blowing around the projectile and slinging debri down bore to boot depositing along the barrel walls.

I firmly believe a proper match between cylinder/barrel to answer all infirmitys aflicting C&B revolvers. That and proper timing of all holes alignment in cilinder with the barrel.

My 2 cents

 

[Gene L]

I've got two Uberti 1861 Navies. One is fine, the other is over-bored. It seats .375 balls loosely and they will come forward and jam up the revolver. The other one is fine and very accurate with .375 balls. My solution was to buy .380 balls and force a ring, and maybe increase the powder charge.

I've had nothing but problems with my revolvers. I forget to turn the gun to the right to avoid primer problems. I'm still learning, but slowly.

 

[M. De Land]

Is this something a typical gunsmith would do?

My Pietta cylinder was sent out alone so this certainly wasn’t done. I’ve been ondered about alignment as I noticed one chamber seemed a bit off.

Well true line boring starts with a blank cylinder that is first set up with absolute tight fitting bolt notches then is installed in the frame. The tight bolt notches index each chamber and the cylinder is clamped in that position then each chamber is bored successively in the same fashion with the line boring spud screwed into the frame hole. The spud holds the boring tool which roughs out each chamber in alignment with the frame and bolt lock up. The next step is to final ream each chamber successively just as they were bored. This allows the guns frame to jig line each chamber in perfect co-axis with the barrel bore through the frame barrel hole.
All I did was make a spud that fit into the frame barrel hole to hold a chucking reamer of .450 so that each chamber mouth would be reamed the same diameter and as close to bore co-axis as possible with out have a blank cylinder to start with. The technique is not actually a full line bore job but does still use the guns frame to adjust what the factory offers the customer in chamber mouth tolerance.
Forcing cones need to be cut from the muzzle with a reaming tool with a two bushing/bearing shaft just ahead of the forcing cone and the other in the muzzle. A "T" handle is in the muzzle end of the shaft and is both pulled and turned to the depth of cut required. The depth of cut should be just enough to allow about half the diameter of the ball to fit into the cone, in my opinion. This minimizes ball jump from chamber mouth to groove diameter to seal of gas quickly and minimize ball distortion.

 

[M. De Land]

Well true line boring starts with a blank cylinder that is first set up with absolute tight fitting bolt notches then is installed in the frame. The tight bolt notches index each chamber and the cylinder is clamped in that position then each chamber is bored successively in the same fashion with the line boring spud screwed into the frame hole. The spud holds the boring tool which roughs out each chamber in alignment with the frame and bolt lock up. The next step is to final ream each chamber successively just as they were bored. This allows the guns frame to jig line each chamber in perfect co-axis with the barrel bore through the frame barrel hole.
All I did was make a spud that fit into the frame barrel hole to hold a chucking reamer of .450 so that each chamber mouth would be reamed the same diameter and as close to bore co-axis as possible with out have a blank cylinder to start with. The technique is not actually a full line bore job but does still use the guns frame to adjust what the factory offers the customer in chamber mouth tolerance.
Forcing cones need to be cut from the muzzle with a reaming tool with a two bushing/bearing shaft just ahead of the forcing cone and the other in the muzzle. A "T" handle is in the muzzle end of the shaft and is both pulled and turned to the depth of cut required. The depth of cut should be just enough to allow about half the diameter of the ball to fit into the cone, in my opinion. This minimizes ball jump from chamber mouth to groove diameter to seal of gas quickly and minimize ball distortion.

As to cone degree of taper, I have cut mine to 11 degrees but think a steeper angle of 7 degrees or so might be a better option for round ball shooting. The 11 degree works out well for bullet shooting in smokeless guns and my worked over Pietta is more accurate them my factory ROA with the 11 degree cone but if I had it to do over I would try the 7 degree cone.

 

[bang]

Dixie has had those same revolver specifications posted on their website for a long time.
I read them with a huge grain of salt.
They may have had some basis in reality at one time but who knows if they still do.
I doubt that they measure each new batch of revolvers that have passed through their shop since those spec.'s were posted,
so I would consider them to be merely representational.
Each and every gun is unique, and how well each chamber aligns with the forcing cone is going to be different with every gun.
But that is why some people choose to accurize their guns.
Some outfits make higher priced competition models for those who want to spend the extra money.
Perhaps if we knew the manufacturer's wholesale prices for these reproductions not including the cost of shipping and taxes,
then we wouldn't be so critical of their spec's.
If the Ruger Old Army were being made today, it would probably cost more than most are willing to pay.
And there's a reason why Euroarms went out of business too, even though the Rogers & Spencer was a fairly popular model
and known for its accuracy.
The current makers probably don't have a large profit margain per unit.
At least they don't have as much competition as they used to, and can sell more guns worldwide to help keep production & quality reasonably high.
If the prices weren't fair then many folks would stop buying them.

Some folks might say that the diameter of the projectile gets bumped up when it gets blasted out of the chamber.
I suppose that there are ways to collect fired balls and examine whether they are actually being engraved with rifling or not as they pass through the barrel.
I'd guess that they probably are to some degree.
But if not, there are always skirted, heeled or bevel base bullets that may be able to better expand when fired.

I still have a Rogers and Spencer 44. First bp I bought. It's 45 years old and still shoots.

 

[jimhallam]

If you study / shoot English percussion revolvers you will find that as a general rule the chamber diameter is 2 gauges smaller than the GROOVE diameter of the barrel. The idea is that the ball has a thin ring of lead sheared off, so that (a) there is an hermetic seal and (b) it stops the balls or bullets from walking forward under recoil.
The M1851 Adams had no rammer and relied upon an oversize wad affixed toi the base of the ball to hold the charge in place. As the popular calibre for the Crimean War was 38-bore (.500") it didn't work very well***, which is why it is not uncommon to find these revolvers fitted with a rammer. (see Pic of a M1851 with a "Brazier rammer"

*** Somewhat embarassing, realising that one was being chased by a Cossack, to have drawn an Adams from the holster (which was on the HORSE) and to just get a "pop" from the cap !
The OTHER problem is that if one had a M1851 Colt often there was not enough knockdown power -- ESPECIALLY if your apponent had a tulwar or assegai ;-)

 

[bang]

I emaied Pietta about this and basically all I got was run around in they said they are just reproductions. It's my belief they don't think about them as being accurate or they would correct this. Or it falls under some liability issue in that if the owner makes the modification to get accuracy and something happen then they are off the hook.
At any rate the higher end like the rem target are held the better tolerances. I just purchased an 1847 Walker and smaller cylinder bore id at issue. Shoots 10- 12 high and 10- 12 right at 25 ft. Easy enough fix. Drill press, good vise a lot of oil and a 0.45 reamer then good polishing gets that 0.451 bore. Had same issue recent rem 1858 na.

 

[rodwha]

If you study / shoot English percussion revolvers you will find that as a general rule the chamber diameter is 2 gauges smaller than the GROOVE diameter of the barrel. The idea is that the ball has a thin ring of lead sheared off, so that (a) there is an hermetic seal and (b) it stops the balls or bullets from walking forward under recoil.

I’m at a loss here for how this differs from chambers that run groove or slightly over. It would still use an oversized ball and shave a ring and otherwise do everything else you just mentioned, but with theoretically be more accurate and create a bit more velocity.

 

[bang]

I still have a Rogers and Spencer 44. First bp I bought. It's 45 years old and still shoots.

Still have mine too. Got it same 45 years ago. Like to shoot it now and then for old times sake.

 

[bang]

I’m at a loss here for how this differs from chambers that run groove or slightly over. It would still use an oversized ball and shave a ring and otherwise do everything else you just mentioned, but with theoretically be more accurate and create a bit more velocity.

Biggist problem with bp guns is build tolerances. A Rem na 44 I just got has a max barrel bore of .446. Another might have .443 or .448. Tis the nature of them. I have a 45 Kentucky and it measures. 456. Only way around it is to do a bit of rework or buy higher end guns. My Rem na 44 target shoots real well. In half dollar at 25 ft and with my aging eyes. It shoots so well I've never checked the measurements. Thing is I have 6 other cylinders from non target models and all of them work just as good. I attribute it to a closer tolerance barrel. The use of oversize balls is to insure a tight gas seal in chamber. If when it leaves it only barely catches riflings there can be a gap between the ball and the barrel max diameter. Riflings are only .003-.005. If ball just catches riflings the pressure could cause the projectile to skip across the riflings loosing its spin. It's best the projectile gets swedged down a bit entering the barrel so it gets gas seal and good rifling engagement by fitting barrel max diameter. In the case of my rifle I upped the ball size to .451 with .020 patch.

 

[Festus]

Just measured my Uberti Walker. Every cylinder was same. Barrel was .002 bigger at bottom of rifling but was about-.008 at top. Recovered round balls seem to have deep rifling marks. Maybe some people over think things? Cylinders all measured.451.

 

[rodwha]

Just measured my Uberti Walker. Every cylinder was same. Barrel was .002 bigger at bottom of rifling but was about-.008 at top. Recovered round balls seem to have deep rifling marks. Maybe some people over think things? Cylinders all measured.451.

I’ll be the first to admit I tend to overthink things. I like to reach a point where I feel things are ideal and/or efficient. What I know is that modern lead bullets run 0.001” over groove diameter. It’s done for a reason. I also know that there are people who compete and claim they see a noticeable difference when they ream their chambers to groove diameter or just over.

I know that soft lead will obturate, but I see there’s a point in which it’s not enough as with the Pietta .31 Rem. Not that any of the other common repros have grossly undersized chambers such as that model, but I figure the act of obturation may likely rob performance, though I have nothing substantial to back this up. Regardless I want things to be right and have things operating as well as can be within reason.

The way I’m reading your measurements is that the chambers run .451”, the grooves about .453”, and the lands about .0443”. My Pietta NMA had chambers of .446” and grooves of .4525”. Your gun has much better tolerances than my did then and still do now as my chambers have been reamed to 449”. If mine measured what yours do I wouldn’t be so quick to want them reamed as the difference isn’t that big of a deal, though I’d still consider it.

 

[BillinOregon]

Interesting thread. I have a new Pietta Remington New Model Army. I measured the chamber mouths and slugged the bore and the chamber mouths are a consistent .446, grooves .451 and lands .440. Guess I should shoot it as is (with .454 balls) before looking into reaming the chambers.