Slugging an 1860 Pietta

[Razor]

Yeah... ANOTHER friggin' question...:groner:

I slugged my barrel...
It's a 7 groove...
How-the-heck can I get a accurate reading on the groove-to-groove diameted in an odd numbered groove situation ???[smilie=b:

I wanted to check the cylinder chambers vs bore relationship.

Also thinking of champhering the front of the cylinder..

I have a STARRETT dial caliper ...

any suggestions greatly appreciated..

Razor
:castmine:

[Kuato]

Hey Razor. If i may ask why you need to slug your revolver for?

The pure lead ball obturates to fit the bore. Piettas usually call for a .454 dia ball. I've had lots of success with .451 dia. & I still get a lead ring when i seat the ball.

I wouldn't champher the chamber mouths if I were you, unless you're having excessive trouble seating the ball. There should be some resistance when seating cuz your also sealing the chamber & keeping the ball from creeping forward under recoil.

Long story short, "If it aint broke, don't fix it".:Fire:

[Razor]

Of course you may ask..
I had heard of some revolvers that supposedly had chambers smaller than the bore diameter..
Therefore, the ball was figuratively rattling down the bore resulting in terrible accuracy..
In my case the accuracy of my revolver seems to be good..acceptable to me so far..so it's just an academic thing.
Just a matter of curosity more than anything else..on how one would accurately determine the bore on an odd number grooved barrel, where I would think, I would be unable to get a true 180 degree reading through the center..

No, no inordinate amount of pressure needed to seat the balls..
It shaves a fine ring of lead from the balls as I seat them..

I think you may be correct..."if it ain't broke..don't fix it.."

Thanks

Razor
:castmine:

[curator]

Simply take your bore slug and see it it slides intoeach chamber. If it doesn't then chambers are under bore size (usually are on Eye-Tailien repros) If you want to get an accurate measurement you can wrap the slug with brass shim stock then measure and subtract 2 times the shim thickness. Alternately you can "spin" the slug while adjusting your caliper/micrometer and get a "ball-park" measurement. There is a member named MacKennen who has all the fancy Vee micrometers and will measure your slug for free if you send it along with a SASE.

Undersize chambers can be reamed out to .001 over bore (groove) diameter or you can load with some kind of filler like cream of wheat that will seal the hot powder gas behind the bullet.

[Baron von Trollwhack]

Even my gen 2 COLT pocket police had a bore, yes BORE diameter, 2 K bigger than the largest cylinder hole. #%$^^!! Italian guns. IT's gone now. BTW if you take the nipples out you can slug the chamber mouths with a roundball and knock them out for measurement and reference to each hole. You can drive a true .451. .454, .456, .457 ball into the bore and look down the barrel for light to show. Get a pretty good idea of what you have, once you test for groove depth by slugging and therefore what you need in terms of ball and cylinder hole diameter. It is in fact common for target shooters to have the chamber mouths enlarged to a certain depth to accommodate some of those outageous cylinder hole/groove relationships if the holes line up well enough with the barrel. Obturation is nice in a 45-70 but if you are using a 10 grain target load for 25 yard target shooting in a .454, don't count on much help from it. Your fit has to be right FIRST for nearly any good shooting. BvT

[Razor]

Simply take your bore slug and see it it slides into each chamber. If it doesn't then chambers are under bore size

DUH !! (sometimes I'm so damn thick] :roll: It's so simple once someone explains it to you...
Thanks curator.


Alternately you can "spin" the slug while adjusting your caliper/micrometer and get a "ball-park"

Done that.. but wondered if it would be close enough to actual measurement to be of any good..


BTW if you take the nipples out you can slug the chamber mouths with a roundball and knock them out for measurement and reference to each hole.

Darn FINE idea..!! Thanks, I'll do that...

Razor
:castmine:

[Razor]

Hi all..
I did as curator suggested,
I attempted to insert the barrel slug into the cylinder chambers, It didn't fit...
The barrel slug is .451
I slugged each chamber per BvT..
2 measured .444-.446
3 are .445-.446
1 is .446-.447
These measurements are with a dial caliper, 90 deg from each other.
So,.. it seems to me I need to open each chamber to .452 ??
Emery paper in a dowel, spun with a drill motor ?
Am I gonna have enough metal on the chamber walls to be able to do this ??
Thoughts please, Gentlemen..

Razor
:castmine:

[curator]

The very best way to handle this is to purchase the correct "chamber reamer" from Brownells. They make a replacable piloted .452 reamer for the cowboy action crowd. It works fine for a cap & ball revolver. You might check with your shooting friends for someone in the same boat to split the cost. Alternately check you local hardware store for 1/2inch rotary files. I have bought several that mike right at .452". Vermont-American brand at Ace hardware. Take your micrometer with you and check their stock. The rotary file is self-centering and will cut quickly down to the constriction under the cylinder bolt slots.

[Baron von Trollwhack]

You must open each hole consistently in depth and diameter so that essentially rules out the sandpaper on a stick. You must correctly align reamer to hole so you must find a machinist to do the work with precision. The hole must be deep enough to accept the ball, while scraping off that little lead ring, and the resulting ball diameter should be a thousandth or two largeer than barrel groove diameter to seal from gas cutting. Measure twice, cut once. BvT