Cylinder re-sizing

[hmeier4799]

I have a Pietta Remington style percussion revolver. The barrel grooves are .370" dia. and the cylinder chambers are .365" dia.
I am thinking of enlarging the chambers to .370" dia. for matching the grooves, using .375" balls.
Or, enlarge the chambers to .375" dia. and use .380" balls. Would the resulting .375" ball diameter be to large for the .370" grooves?
I do not cast. Therefore, I have to use either .375" or .380' balls.

 

[R.M.]

Those balls will squeeze down .005" with no problems as long as they're soft lead as they should be.

 

[LRB]

If I was going to do that, I think I'd go .371, or even .372, and modify, or polish the forcing cone.

 

[Zonie]

I've always been told that the bullet (or ball) should match the groove diameter in the barrel for the best accuracy.

Based on this I would say the cylinder chambers on your gun should be .370 .

 

[LRB]

Most lead bullets are + .001, as are many jacketed bullets in modern firearms.

 

[Dphar]

I have a Pietta Remington style percussion revolver. The barrel grooves are .370" dia. and the cylinder chambers are .365" dia.
I am thinking of enlarging the chambers to .370" dia. for matching the grooves, using .375" balls.
Or, enlarge the chambers to .375" dia. and use .380" balls. Would the resulting .375" ball diameter be to large for the .370" grooves?
I do not cast. Therefore, I have to use either .375" or .380' balls.

Does it shoot OK?
How deep is the rifling?
Are you shooting CAS loads or a full charge?

If the rifling is deep it may well deform the ball enough to fill the grooves and work OK.
BP also tends the bump up bullets but may not do much once it is in motion.
Finally you can likely enlarge them with a "split stick", some 220/320 grit wet or dry and an electric drill.
Having a plug gage is nice so the actual size can be determined as you work. Just make sure the paper is all the way in while its turning or you will "bell" the chambers. Finish with 600 grit.
In any case there is no need to enlarge past the groove of the barrel. This smokeless powder stuff.

OR you could sell it an buy different revolver
.

Dan

 

[Flash Pan Dan]

I agree with Dan Phariss. I shoot a pair of Pietta Remingtons and I was going to make the same modification you are thinking about until I work up a load that was strong enough to upset the bullet and light enough to use in CAS. That turn out to be 29 grains of 3F Pinnicle in my pistols. But I encourge you to test out different loads as it may take a little less or a little more for your pistol to shoot well. With this load I can get 2 inch groups, from a rest, at 25 yards.

 

[CoyoteJoe]

I'm surprised your bore is so small, most I've seen run at least .375" groove diameter. Under-size chambers are common, some so small that a ball rammed in and pushed back out will actually fall through the bore and accuracy is hopeless. Reaming chambers to full groove diameter will certainly improve accuracy.

 

[kwilfong]

I haven't tried it on a .36 yet but had good results opening up the chambers in a .44 with a .453" reamer.

 

[BGRooster1]

My Pietta .31 Remington Pocket Pistol is .315/.323 and I also have thought of reaming the cylinder.In my mind I see the ball doing a pinball imitation down and out the barrel.lol Not expecting a tack driver.I just enjoy an accurate firearm.

 

[kwilfong]

Interesting! I just bought a CVA pocket Remington & started a thread on it. I'll check the clyinder/groove dia. relationship when I get it. I know some have good results shooting C&B revolvers with chamber diameters smaller than barrel groove diameter but it just doesn't make sense to me to make one that way. My ROA chambers are slightly larger than groove dia & that seems right to me.

 

[BGRooster1]

I wonder if the oversize bore is not some kind of CYA for the manufacturer.Kind of limits the pressure that can be produced. :idunno:

 

[CoyoteJoe]

The bores aren't oversize, the chambers are undersize, but you're probably right that it is a CYA measure, more likely to assure the ball will seal the chamber mouth against chainfire.

 

[hawkeye2]

I just spent quite a bit of time composing a reply to this post only to loose it when I hit the preview button and got a screen that said "cannot find the server". Yeah I know; do it in Word. I'll try again.

You will need to ream your chambers slightly under the size of the ball you use. I have my .44s reamed to .4560- for a .457 ball and this loads easily. A friend did the clyinder on my wife's Uberti Remington and he got one at .4565. The ball in that chamber will walk foreward under recoil every time and lock the gun up. Solution; I numbered the chambers and she shoots that one first. The forcing cones on all the repro revolvers I have ever examined are way oversize probably to compensate for potential problems elsewhere so you shouldn't have any problem there. I recut all mine to a gentler angle and a smoother finish and have no issues with swedging the ball down to bore diameter, usually about .454, as it passes through the cone. I am sure it ncreases the pressure slightly but I never shoot above 22 grains of 3f with Cream of Wheat as a filler to space the ball out to the chamber mouth. Given the cylinder/barrel gap acting as a vent and that the ball is moving quite fast by the time it reaches the rifeling I doubt that it gets bumped up much.

Are you sure of your measurements? An easy check is to drive a ball thorugh the barrel and check to see that it has filled the groves. Try the ball in a chamber, it should enter easily with no shaving, marking or effort. If you encounter those your chamber is too small.

If you decide to have the cylinder reamed contact me and I can give you contact info for the smith that has done my last 3 cylinders. Excelent work, $21 delivered to my P.O. box. I wouldn't even think of doing it myself for that price.

 

[kwilfong]

I've got a .4535" reamer that I used on a Pietta Target Remington. It worked out good & made a fine shooter.

 

[nilo52]

I have one too, but mine shoots O.K. I will have to check mine now (I will not rest till I do, not knowing bugs) just to see what they are. I always use wads to do for chain fires.
nilo52

 

[nilo52]

Just measured my pietta, cylinder is .448, barrel is .444 :grin:
nilo52

 

[BGRooster1]

Would relining the barrel be an alternative?Just a crazy thought.

 

[D Sanders]

I had the same problem with an ASM Colt Walker. The chambers were bore diameter and the ball was not cutting into the rifling. I opened up the chambers till I got them to cut about .002 under the groove diameter. Before I altered the chambers I could only get about 6" at 20 yds. Now I can cover my groups with an 1 1/2" diameter circle. I Would start by opening the cylinder chambers up to about .002 to .003 under the groove diameter. You can always open them up larger if you need to, but I think you will be pleased with these results. :wink:

HH 60

 

[D Sanders]

Would relining the barrel be an alternative?Just a crazy thought.

That would work, but opening up the Chambers is much easier and cheaper. A good machinist/ tool and die maker can make the chamber diameters anything you want. Trick is to find one of these fine gentleman that will do the work for you.

HH 60