Huge barrel to cylinder gap on a new 1858 Pietta

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Mizar

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Hello. Recently I bought a nice 5 1/2" Pietta 1858 New Model Army from Cabela's. I have not shoot it yet - mainly because I do not have time. So, the barrel to cylinder gap measures 0.02" (0.5 mm). What can I expect from this excessive gap in terms of velocity loss, lead spitting, fouling and etc? Me and a friend of mine bought two 5 1/2" Piettas and both have the same gap. The revolvers have no other problems - timing is excellent, the inside and outside are finished very well - the revolvers needed just minor adjusting and polishing of the internals (bolt, hand and hammer). I do not want to return it to Cabela's - except for the gap the revolver is mechanically flawless.
The real question is - can I live with such a huge B/C gap or should I unscrew the barrel and adjust it?

Thank you in advance,
Boris

P.S. I am new to the world of Black Powder shooting so do expect lots and stupid questions in the near future...;)
 
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Not sure if you have a problem or not. 0.2 inches is 5 mm, not 0.5 mm. Your barrel to cylinder gap is either 0.02 inches (0.5mm) or 0.20 inches (5.0 mm). If the former you have no problem; if the latter there is something seriously wrong with the gun and it should be returned to Pietta.
 
mykeal and arcticap, my bad - 0.02 inches - I am in the metric part of the world and confused mm with cm for the conversion :eek: the gap is 0,5 mm - measured with a feeler gauge. Like I said - this is my first C & B revolver and compared to modern revolver the gap seems excessive. Thank you both for the answers!

Boris

P.S. I am going to edit my post because of the embarrassment...
 
Now that you have the barrel gap dimension cleared up, leave it alone. First off, if you were to screw in the barrel a turn, it would create a problem latching the loading lever. Secondly, the cylinder on BP revolvers slides forward and closes the gap because of the hand spring before the firing. A gap is necessary so the cylinder face doesn't jam on the back of the barrel due to the black powder fouling and make the gun almost impossible to re-cock. Just make sure that the hammer can still fire a cap when the cylinder is in it's forward most position.
 
junkman_01, that is not an answer to my question.
1. If I face the front portion of the frame and screw the barrel one full turn there will be no real problem with the loading lever - if there is some interference with the latch the problem will be solved with 10 minutes work with a file followed with a cold blue.
2. The endshake of the cylinder is almost non existent - it will put a Colt to shame. If your revolvers have so much endshake as you described I suggest a visit to some gunsmith for correction.

Best,
Boris
 
On an open-top Colt style revolver, when you cock the hammer, the pressure from the hand pushes the cylinder forward a bit, so the gap is narrowed when the gun is fired. I don't own a Remmie 58, so I can't check to see if they do the same thing, but I'm curious...does the gap narrow any when you cock the gun?
 
When the gun is fired the recoil forces are pushing the cylinder back and the gap is at its biggest measure again. Like I said - The endshake of my revolver is almost non existent - it will put an (old) Colt to shame.

Boris
 
I'm with madcratebuilder -0.02" is twice what I want in my revolvers, but it's a whole lot better than 0.20"!

As far as 'repairing' the problem, that depends entirely on what's causing it. Is it a tolerance stackup (all parts are dimensionally in tolerance but near the limit such that the sum exceeds whats acceptable), or is it due to one part being out of tolerance? Fixing the assembly to correct one part being out of spec is generally not a good solution. Unfortunately it's difficult to make that determination without a good example to compare it with.

The lack of significant endshake makes me think the problem is with the barrel - the cylinder fits with the frame and arbor assembly. That suggests turning the barrel might work. However, I'm not at all sure there is enough thread length to support a full turn of the barrel. If there is, it was just installed incorrectly, which isn't all that hard to imagine. But if the barrel is installed properly, and there isn't enough thread left to turn it down, then the problem is an out of spec part, and the solution is to replace it.
 
On an open-top Colt style revolver, when you cock the hammer, the pressure from the hand pushes the cylinder forward a bit, so the gap is narrowed when the gun is fired. I don't own a Remmie 58, so I can't check to see if they do the same thing, but I'm curious...does the gap narrow any when you cock the gun?
On my Remmie the gap closes when cocked.
 
Hello,

I bought once a 1858 Pietta with a 0.5mm gap as yours ; although I could have done with it, I sent it back for a replacement : the one I received in return had a very tight gap but chambers / barrel alignment was not perfect ......... However I kept this one.

- As for the 0.5mm gap it is not optimum but managable

- As for turning the barrel, you will have to turn it one full turn and then grind the face of the barrel facing the cylinder ; however in my experience, there is a gorilla in Pietta workshop who is in charge of screwing these barrels and you may face great difficulties when unscrewing it.........

good luck
 
mykeal and flibuste, the barrel's thread length is out of spec and it can't be screwed further that this. I can correct the problem in two ways:
First way (which I prefer) - remove barrel, grind the front of the frame with a mill the desired length needed for one full turn, adjust overall barrel length and forcing cone on a lathe (good enough for this revolver).
Second way - grind the barrel in front of the threads on a lathe to the desired length needed for one full turn. Everything else - like the first method.

But the real question is - is it worthed? If you have a revolver with similar B/C gap how it is performing - do you notice considerable velocity drop, excessive fouling and leading, bad accuracy?

Boris
 
That's actually pretty standard, and won't hurt anything.I've had repros from the '70's that had gaps as much as a 1/32'' on one opentop, and it worked just fine.
 
If the gap is TOO tight, fouling will make the cylinder bind up after ten or twelve rounds. I'd leave it alone, if it were mine.
 
And I did reply to you, junkman, in post #7... Do you really get the difference between NO gap at all, a 0.005 - 0.006" gap (which is more or less standard these days) and a 0.02" gap?

Boris
 
Boris,
YOU are not getting it. Just leave it alone and shoot it. You will be making more trouble for yourself if you start messing around with it, because I fear you do not understand how the C&B revolver is supposed to work. You continue to compare it to a modern revolver, which it is not.
 
That is a very large gap.

using .454" dia. and .020, that gives a cyl. wall area of 0.028526 sq. in. area in the gap.

a circle .190" in dia. has about the same area.

that would be about like drilling a no. 11 sized hole in a rifle barrel just over the loaded ball.
.034 bigger then a 3/16" hole. no 11 bit (.191)

that's a big leak.

I read an article on the web where they reset the gap on a SAA from .006" to .002" and the chrony results gained 100 fps muzzle velocity.

and this guy gained 100 fps per .001" that the gap closed in tests with a 357.
So even though were talking BP revolvers here the velocity loss could be a fair amount.

http://fiveshot.org/backissues/paco/velocity.htm
 
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Junkman, I am getting a little tired from this. I did not ask what you consider to be optimal or to give me an advise not to do it. I did ask a specific question and you did not answer it. From my searching the "standard", common, B/C gap on a new Pietta NMA is between 0.005 and 0.007" and quite a few people are living happy with it. I am not asking you for opinion on my machining and gunsmithing skills so, please, keep it to yourself.

Best,
Boris
 
Hello. The real question is - can I live with such a huge B/C gap or should I unscrew the barrel and adjust it?

Thank you in advance,
Boris
This what you asked in your first post and I tried to help you and answered your question. Leave it alone and just shoot it.
 
You can return your Rem. to Cabellas even if it has been fired, but not if it has been modified. Just shoot it. If it does not meet your expectations just send it back. Piettas are not perfect, but for the price they aren't bad. I have issues with barrel not being indexed properly on my Pietta Army, but considering the groups it will shoot, I can live with it. Enjoy, don't worry:)
 
I just measured the barrel to cylinder gap on my own '58 Remington (made by PR, brass frame) and it measures .016 inches. It shoots just fine thank you.
 
Wow...and all this time I thought the gaps on mine, .006 and .007...were excessive!
Mizar...Junkman is trying to help you by getting you to use some common sense in that shooting the gun first is the smartest action to take. After that, if you are not satisfied with it's performance, then you can either modify it as you wish (it's your gun) or return it to the place of purchase. Myself, I would return it with a gap that large!
Getting defensive or arrogant with others trying to help you isn't going to get you much advice in the future so you might want to relax a little bit.
 
Wow junkman, its seems conflict and strife follow you around. Two threads in as many days. I used to respect your posts, but I may need to re-think this.
 
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