Chamber & ball size

[hmeier4799]

Regarding percussion revolvers: What should be the relationship among the sizes for the ball, cylinder chamber, lands diameter & groove diameter?
Dixie's catalog shows Uberti's groove depth to be about .010" or groove dia. .020" larger than lands dia. isn't that excessive? Blow-by if the
ball does not fill the deep groove?

 

[jim gray]

The chamber actually sizes the ball on loading so that should create the optimum size ball for the barrel.

 

[LRB]

That's assuming that the chamber is of the correct size. Many are not. Many are too small, and swage the ball down smaller than the bore. This is the first thing to check if you have accuracy problems.

 

[hmeier4799]

Rephrasing my question: For 36 cal. (.360" lands dia.) what should be the diameters of the chamber and the grooves?
Is .010" (.020" total) to deep for the grooves?
What dia. should the ball be?

 

[SAJones]

Many years ago, thre was an article in Muzzle Blasts about the relationship between chamber diameter and bore diameter. He grew up shooting an original, & couldn't get the accuracy he was used to with replicas. So he measured original Colts & noted they had a greater chamber diameter than bore diameter, but the replicas had the chamber diameter identical to the bore (or smaller). So he reamed out the cylinders on several repros & improved the accuracy considerably. Thus, the ball when fired would swage down to the bore diameter, no blow by, no "stripping" by the lands.
I don't have those back issues any more, so can't say what he bored the .36s out to. I would surmise about .001 or .002 larger than the bore (groove-to-groove). Something I wanted to try out, but couldn't afford the reamers. Even standard sizes are expensive.
I will say the one Colt repro I have w/ a larger cylinder than bore, an 1862 Police Pocket, is quite accurate for a revolver of this size. Put a new front sight on it & even used it in matches for fun.

 

[Zonie]

IMO if the bore is .360 and the groove dia is .380 the ball should be at least .375 and better yet it should be .380.
This would mean the chamber should be .380 and the actual ball (before loading) should be .385.

The actual depth of the grooves varies with different makers and I am basing my comments on the sizes Dixie lists for the Uberti 1851 Colt.

Dixie also mentions the chamber diameter for this gun is .372 which bears out what Wick was saying.

Looking at the Ruger Old Army, it has a bore diameter of .443, a groove diameter of .451 and a chamber diameter of .453 which helps explain why it is IMO such an accurate gun.

 

[John Taylor]

Best to slug the barrel to get the groove diameter. A ball should be placed in the barrel and a brass rod from each end, hammer on one brass rod to exspand the ball and then push it out and check it with a micrometer. This is a little hard on a Remington so you might try an over sized ball and a wood mallet to drive it into the muzzel end on through the barrel with a wooden dowel or brass rod. Cylinder should be reamed to .001"- .002" over groove size. I have done this many times on Colt reproductions and it helps a lot. Reamers can be bought at[url] http://www1.mscdirect.com/cgi/nnsrhm[/url]
Look under chucking reamers. Or you might try[url] www.use-enco.com[/url] . MSC has more sizes but they run about $25.

 

[LRB]

If you only have to go .002, to .004, to get the right size, this can be done by hand with a dowell and automotive wet and dry paper, 220 grit. It takes a little time to do all six, and you need a ball or rod of the desired size to use as a gauge. You do not have to open the chamber much below where the ball sits.

 

[JIMinPHX]

Reamers from MSC are generally of much better quality than the ones from Enco. I usually get L&I reamers from MSC for stuff that I want to come out nice. If you buy from Enco, only get name brand stuff. If you buy from MSC, then even the economy/import stuff will be useable.

When using a reamer, be careful to keep it dead straight with the hole that you are reaming. It is very easy to egg shape a hole or to make an oversize hole if you do not keep it straight. I usually use a 2-point support fixture when reaming parts by hand. My preferred method is to chuck the reamer in a Bridgeport after locating hole center with a test indicator or wobble feeler. If nothing else, clamp a piece of wood down on a drill press table that is square & drill a hole of the proper size in it. Then clamp this wooden guide on the front of the revolver cylinder that you are going to ream so that when the reamer passes through the hole in the wood, the reamer is held straight.

Reamers usually don’t like to take much more than .008” or .010” maximum out of mild steel in a single pass. If you need to remove more than that, then get two different size reamers & do the job in two steps. Use plenty of oil on the reamer & don’t try to go fast if you run it with a power tool. About 40 RPM is as fast as I ever run them, even in a Bridgeport with everything properly lined up.

The wooden dowel & sandpaper trick needs to be done carefully if you choose to go that route. It can give you uneven or out of round results otherwise. It is also very hard to keep the shoulder of the bore sharp when using this method, which can make it hard to shave off the ring of lead when you load a ball.

Regards,
Jim

 

[Zonie]

Another comment on using the dowel and sandpaper method:
Where the reamer will cut to within a few ten-thousanths an inch of it's known size, the sandpaper method is uncontrolled.

The amount of wall between the cylinders on the .44 caliber guns is very thin as it comes from the factory. As you remove material from the inside of the chamber you are decreasing this small thickness and because the process is uncontrolled it is easy to take too much material and make the gun dangerous to fire.

How thin is too thin? Damed if I know but remember, that thin wall has to withstand thousands of pounds per square inch of pressure when the gun is fired.

Just something to keep in mind while your frinkleing with things.