pietta 1858 .36 cyl./bore size question

[schreck5]

Ok guys and gals, I now have my new Pietta 1858 .36 in hand. Hated the trigger so had my 'smith work it over. He did a great job!

The bore slugs at .375 after passing through the threaded area of the bore. The cylinder slugs at .368. Do I need to ream the cylinder or just wait till I see what it shoots like?

 

[FishDFly]

Ok guys and gals, I now have my new Pietta 1858 .36 in hand. Hated the trigger so had my 'smith work it over. He did a great job!

The bore slugs at .375 after passing through the threaded area of the bore. The cylinder slugs at .368. Do I need to ream the cylinder or just wait till I see what it shoots like?

To borrow one of Zonie's terms, why frinkel with a new pistol that has not been shot?????

Most folks recommend a .375 ball as that is about all that is sold retail for .36 pistols.

Buy a mold and shoot .380.

 

[F.G. Ford]

Hi,
To get the best results of your bore diameter, is to squeeze a ball ( a little ) in a vise.
Rub some lube down the barrel.
Then with a soft hammer drift the ball down the barrel ( remover cylinder first ) then mike the ball for best results.
If it reads .375 then consider reaming the cylinder larger.
But as the previous post suggests, try it first with store bought balls first.
Go slowly, remember, you can never go back, in an operation like this.
Fred

 

[ccmountainman]

The bore slugs at .375 after passing through the threaded area of the bore. The cylinder slugs at .368. Do I need to ream the cylinder or just wait till I see what it shoots like?

============
I find it difficult to believe the cylinder chamber is .007 SMALLER than barrel bore diameter (land to land).
The ball would be like a bowling ball down a gutter.
No matter how BIG a ball you pressed into the cylinder chamber it is still only going to be .368 when it leaves (using your dimension).
Land to land in the bore should be about .360 (thus 36 caliber) and the groove to groove (presuming 2 grooves are exactly 180 degrees opposite) would be .370 to .372 on average. Again using your figure of .368 chamber diameter.
The properly machined forcing cone will "roll" back the excess diameter of the ball as it enters the barrel, creating a small ring. It is this ring that then fills in the gap of the grooves.

The older pietta 44's only had 5 lands and grooves.
Thus two grooves were never exactly 180 d apart.
Thus in measuring the barrel bore you took the land to land diameter, added in the depth of ONE groove.
The new 44's now have 6 grooves, so it is possible they could have two exactly 180 d apart.
But looking at them, you can see they are definitely shallower than the old.
I don't know if they also went to 6 land and groove on the .36 cal.
You need a spherical tipped bore gauge or a split ball gauge to properly measure your chamber and land to land bore diameter.
Measure in a couple different areas of the chamber to confirm uniformity.

 

[schreck5]

Yes, I find it hard to believe there is a .007 difference too. Must be operator error. I wish, now, that I would never have checked it. :hmm:
I think I am jumping the gun by trying to fix something before I shoot it. Big tu-du over nothing.
Thanks everyone for setting me straight.

 

[Tinker2]

Let us know how it shoots

 

[Flash Pan Dan]

My Pietta New Armies have .452 groove and .448 cylinders. No problem. Though I did find that the more powder I use the better the accuracy. The charge must be obtruding the ball enough to make it work.

 

[rodwha]

My Pietta Remington (2013 model) had .446" chambers and .452" groove. It shoots better with 30 grns of 3F Olde E or T7. I did have the chambers reamed to .449" partly as many believe it ought to be roughly groove diameter, but also to not stress the loading lever assembly as I share my .456" conicals and .457" RBs with my Ruger.

 

[nhmoose]

No one can ream or remove metal smaller yes bigger no. DUH!!!!!!!!

 

[curator]

Osage Orange: It is not unusual for a Italian repo revolver to have chamber diameters smaller than the groove diameter of the barrel. If you want a truly accurate Cap & Ball Revolver you are supposed to by the "Shooter Model" that is made with the correct chamber diameter. One can only assume the lawyers are worried about chamber pressures after "dumb-cluck Americano" loads the gun with the nipples cross threaded and gets injured. If your bore/groove diameter is .360/.375, the correct chamber diameter is .376-.378". Reaming the chambers to this diameter (assuming this could be done correctly) and using .380 diameter round balls will give better accuracy with all loads. Yes, you may find reasonable accuracy with heavier loads and hoping for smaller balls to obturate to seal the bore. Using fillers like cream of wheat or corn meal under the ball will also seal the under-size ball in the bore and provide reasonable accuracy.

 

[AZbpBurner]

I cast .375" RB's for all my .36 cal cap & ball revolvers. My Remington does just fine with them.

Quit overanalyzing your supposed dimensional foibles and actually go shoot. You'll find that accuracy will be superb using 17 gr 3F, and a lightly greased paper wad (or even a WonderWad) between ball & powder.

Your biggest concern will be how much of the front sight to file down to bring the ball to your desired POI.

 

[M. De Land]

More importantly check that all the cylinder mouths are the same diameter and are round.
I can't remember when I have found a cylinder with all the same diameter chamber mouths and quite often are not perfectly round.
This is because they are gang reamed at the factory and factory reamers use wear tolerance so they are not all exactly the same.
The proper tools to check chamber mouths and bore diameters are hardened steel plug gauges.
Uneven grooved barrels are checked with a driven slug and either tri-miced or Powely gauged using a standard mic.
Also nearly all factory guns have tighter bores(land diameter) under the barrel threads than they are at the muzzle and accuracy suffers from this. It can be lapped out and is good practice to do so.
The primary reason for this is over tightening the barrel threads when installing.

 

[nkbj]

Check the reaming depth on the chambers also.
I have a .44 1858 Pietta that you can see the difference in depth from chamber to chamber just by looking at it with good lighting. Verified the differences miking each hole. Could easily do the same using a dowel rod. The reamers they use are tapered. Depth changes diameter as well as powder volume. Haven't gotten O2it on reworking the cylinder yet.

By the way, the geometry of the rifling and not just the groove diameter determines how well any given chamber diameter will work for you. The narrower the lands the more it can need the larger chamber diameter. Narrow grooves not so much.