Drilling Out Chambers

[LRB]

It was a pretty common problem years back, with a great number of percussion revolvers, of all makes I know of. The machining was not necessarily bad, but the specs to machine to were often incorrect. If far from a common problem, how do you explain it being common knowledge to check for it?

 

[nkbj]

Well, to use a reamer even to get the chambers out to groove diameter I'm gonna have to drill first to bring the chambers up in diameter to keep from pushing too big of chips with that small of a reamer. The O size drill will be a good place to start. If it doesn't shoot at .316" I'll see about a .321 or .322 reamer.

 

[Artificer]

Is it true that only one cylinder chamber is used if one wants to achieve maximum accuracy in a C&B revolver?

A few years ago I was shooting one of my MLers at the gun club and this guy comes over and wants me to shoot his C&B...complained that he wasn't satisfied w/ the accuracy.....some "fliers".

He handed me the loaded gun and I took 3 off handshots at 25 yds and had a 4" group and was about to hand it back to him when he asked if I would shoot 3 more rounds. The next shot was a "flier", the next one was in amongst the previous group and the last was another "flier.

Repeated shooting 6 rounds and the same thing happened. Didn't mark the 2 errant cylinders, but told him he should do it. Don't think it was the cylinder dias., but do think it was cylinder orientation. Could be wrong and it was the cylinder dias. Comments?. Not up on C&B revolvers.....Fred

Hi Fred,

I am just barely old enough to have seen some of the last really good Revolver Shooters in NRA 2700 Bullseye Pistol Shooting. They fired rapid fire competition in 5 round strings and those shooters made a point of firing their revolvers with each chamber and leaving out the least accurate 1 of the 6 chambers. They usually had that chamber marked in some way so they did not load one of the five rounds in that chamber. This was done with each one of their .22, .38 and .45 Smith and Wesson Revolvers. So even with modern guns made to much higher quality standards than we find on Repro BP Revolvers, there was/is a difference in accuracy of the chambers.

From the folks who shot Original Remington M1858 .44 cal. BP Revolvers in NSSA and International Muzzleloading Competition, they found the same was true with those revolvers. And yes, if a match was slow fire and if therr was enough time to do so, they only loaded the most accurate chamber to shoot in a match. Otherwise, they would also not load the least accurate chamber.

I have also seen NSSA shooters mark or engrave their cylinders in various ways, often with numbers, to tell them which were the least accurate chamber holes in their Replica BP revolvers.

So, yes, it is entirely possible that the most accurate shooting from a revolver could be from shooting just one or a few chamber holes.

Gus

 

[Artificer]

It was a pretty common problem years back, with a great number of percussion revolvers, of all makes I know of. The machining was not necessarily bad, but the specs to machine to were often incorrect. If far from a common problem, how do you explain it being common knowledge to check for it?

Chambers possibly being undersize or over size were just two of many things a "Revolver Smith" checked/checks when accuracy is a problem. When I was at the Smith & Wesson Armorer's Academy in 1984 and we started the course with five barreled frames with the yokes barely fitted and then built them by fitting all the other parts, Cylinder Bore Size was one point they mentioned to check even though it was extremely unlikely it would be a problem and it was done after the rest of the check list was completed.

The best modern and BP revolver smiths have ranging rods to check for cylinder to bore alignment for each chamber cylinder. Is that a common problem on modern or BP revolvers? Well, it depends on what level of accuracy or serviceability one requires/uses and the level of accuracy one is attempting to get from the revolver. IOW, there is a whole checklist one goes through on checking modern or BP revolvers for serviceability and accuracy and chamber hole dimensions is just one of the checks performed when a revolver is not shooting well.

One very common accuracy enhancing modification done to both modern and BP match revolvers is to chamfer the throat of the barrel to make up for small differences in the way the chamber holes align to the barrel. Is or was that needed for every competition modern or BP revolver? No. The modification actually started the most in PPC shooting and then was transferred to BP revolvers. It became an almost "have to do" modification on every BP Revolver for those who wanted to win in the higher/highest levels of BP revolver completion, though. The exception to that was/can be if the competition did not allow the modification because it was not done in the period, as International Muzzleloading Rules often state.

Gus

 

[Scota4570]

I did not see the bore diameter, did I miss it. If the chambers are already larger than bore why mess with it? Shouldn't the bore be measured before we discuss drilling an reaming?

 

[Pete G]

I see no mention of a range rod to check cylinder alignment, either before or after the proposed modification. If one chamber is off from the others by only a few thosanths it will be a guaranteed flier.

Assuming the roughness is concentric with the chamber I don't really see any problem with it. Might even be a good thing to add a little bit of grip to hold the balls in place on the unfired chambers.

 

[Zonie]

On a Cap & Ball revolver the chambers in the cylinder should be the same size (give or take a thousandth of an inch) as the rifling groove diameter.

The bore is always smaller than the chamber in the cylinder. If the chamber was bore size or smaller, the ball would skip thru the bore without picking up the rifling.

 

[M. De Land]

Arghhh, not if you want a round hole Fred. Drill bits do not accurately ream and they seldom make a hole round.
That is why drilled holes are always reamed for precision work like barrel bores or pins for false muzzles for a couple of examples.
Reaming's primary function is to make a drilled hole round, not just to smooth it up which it also does.
A reamer will make a perfectly round hole if used correctly. Mike D.

 

[crockett]

Gus- you sound like a guy that knows his stuff. Could you explain a few things? On chamfering the back face of the barrel to help the balls enter better in case the cylinder is a little off. How is that different from the forcing cone? I thought that was one function of the forcing cone.
I think there is always a little play side to side on the lock up of the bolt in the leade/notch so it seems to me there will always be a very slight variation as the ball leaves the chamber and enters the barrel.
That idea I had on affixing some sort of polishing head to the end of a range rod- I guess that must not be a great idea as no one has commented on it but theoretically I thought such a method would insure the chamber polishing was in perfect alignment with the bore. How to set it up- that might be a different issue.
On the chamber diameter, is there an actual "perfect" formula? In other words if chamber diameter is the same as groove diameter- there will be no gas cutting- that ought to be ideal however the ball will get squeezed a bit from the rifling. If chamber diameter was a slight (.001" etc.) undersized, there might be some gas cutting until the ball molded to the bore and created a good seal.
On the cylinder lock up- I have assumed the bolt should be shaped with parallel sides but I suppose a very slight trapezoid shape would eliminate any side to side wobble although the bolt spring might need to be a little heavier.
IAE- any information welcomed.

 

[M. De Land]

Chamfering a chamber mouth a bit will hurt nothing but a forcing cone should only have the sharp edge of its circumference broken and no more, especially if the revolver is of the solid frame design having a top strap as the forcing cone chamfer encourages gas leakage from the cylinder/barrel gap. It will gas cut over time to a certain degree and will usually spit out all the way around more than if not heavily chamfered.
Range rods do not really tell you much. A plug gauge set in .001 progression will tell you much more.
I have several range rods for .38,.44 and .45 but find them almost useless as they will slip right on buy misalignment that can easily be picked up with the naked eye and a goose neck auto light.
They will pick up gross misalignment though.
I don't think I have ever seen a production revolver with perfect alignment and I've looked at a lot of them.
I have also serviced revolvers with very poor alignment that shot quite well.
Perfect alignment is always desired but more important than perfect alignment is consistent alignment of each chamber.
If they are all a bit off but are equally misaligned that revolver can shoot very well.
I have a friend who is one of the best pistol shots from a bench I have ever heard of. He has owned over fifty different Cassule revolvers in all caliber as well as several custom guns.
Cassule revolvers if you are not familiar with them have a stellar reputation for both accuracy and power. One of the very finest brands of semi- custom guns.
He told me once about 10 years ago or so that he has owned just three that were consistent minute of angle guns at 100 yards. They would do it day in and day out.
The others would do it sometimes but not all the time.
This level of accuracy is only possible with near perfect alignment and dimensional uniformity.
Denis could not afford to keep more than one gun at a time being a family man so he just kept selling them off so he could test another to it's peak performance and down the road it would go.
I asked him once why he didn't keep the best and he said he enjoyed the accuracy quest and once achieved the gun lost interest for him. Mike D.

 

[LRB]

I fully agree. MD is quite on the mark with the above. An actual chamfer will cause problems, and changing the angle of the cone may create a compound angle, often ruining the forcing cone. If you want to try to improve it's effectiveness, do no more than polish the interior wall, and clean it well after a shooting session. Some can be improved by a steeper/deeper angle, but not all are viable candidates for this, and can be ruined by doing it.

 

[crockett]

Thanks to all for the information. I never thought about increased gas cutting. All of this does sort of lead to something that I generally feel. First, always look to the load, ammunition. Second, there seems to be an eagerness to rush in and modify firearms with the results often being negative. Be careful of what you wish for.

 

[mazo kid]

I have a question....it was stated early on that when reaming a cylinder chamber the reamer would not go all the way to the bottom and a second reamer would need to be used. Why? The ball only goes part way into the chamber anyway. If we are just trying to get better accuracy through chambers that are identically sized then I would think we are done. Chamber to bore alignment would be the most important aspect for accuracy, IMHO. Just thinkin' out loud here.

 

[LRB]

You are correct as far as percussion revolvers. Reaming could stop at about the lowest depth of any seated ball, or bullet.

 

[crockett]

I'm not certain but I thought there was a slight dish shape to the bottom of the chamber, You might need a special reamer to do the entire chamber.

 

[LRB]

True Crockett, and I don't see where that would necessary, but if it was, Fred's method may serve to do that.

 

[Zonie]

Standard reamers are not designed to cut the face at the bottom of a blind hole. They are only made to enlarge the hole by a few thousandths of an inch.

A good design never requires a reamed tolerance or finish clear to the bottom of a blind hole.

As far as reaming the chambers on the cylinder of a revolver goes, there is absolutely no reason to do it.
The ball will never be loaded all the way to the bottom of the chamber unless the shooter forgot to put the powder in first and reaming that last 1/4 inch won't help the dry ball loads shoot any better.

 

[nkbj]

Gentlemen,
Had to take a break and give this the long look. There's no reason to screw it up. Going to contact a GOOD smith to do this. Thank you for the input.
Reckon now I get to figger out the chamber diameter and mold.
Never had such a long barrel on a .31. The 4" that I shot in the seventies was crude but cool. This little rascal reminds me of a Ruger Bearcat and I want to make it as accurate as can.

 

[hawkeye2]

I never could understand why no one ever made but a couple of runs of the '49 with the long barrel. I have an EIG with a 4" but would grab a 6" in a New York Minute if they were in production. It's the aesthetics of the long barrel percussion revolvers, not to mention their balance that holds the greatest appeal to me.