Huge barrel to cylinder gap on a new 1858 Pietta


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Mizar
December 18, 2010, 04:18 AM
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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mykeal
December 18, 2010, 05:49 AM
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.

arcticap
December 18, 2010, 05:56 AM
Since there's 2 identical guns, I'll wager that it's only a misplaced decimal point and not a gross defect. :)

madcratebuilder
December 18, 2010, 06:14 AM
A barrel gap of .020 inch is twice what I would expect. A new BP revolver should be around .006-.008.

Mizar
December 18, 2010, 06:22 AM
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 :o 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...

junkman_01
December 18, 2010, 06:49 AM
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.

Mizar
December 18, 2010, 07:30 AM
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

J-Bar
December 18, 2010, 09:49 AM
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?

Mizar
December 18, 2010, 10:21 AM
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

mykeal
December 18, 2010, 12:17 PM
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.

junkman_01
December 18, 2010, 12:40 PM
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.

flibuste
December 18, 2010, 12:45 PM
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

Mizar
December 18, 2010, 01:33 PM
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

BHP FAN
December 18, 2010, 01:53 PM
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.

GCBurner
December 18, 2010, 02:03 PM
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.

junkman_01
December 18, 2010, 02:35 PM
I told him all that in post#6. He just won't listen.:banghead:

Mizar
December 18, 2010, 02:45 PM
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

junkman_01
December 18, 2010, 03:04 PM
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.

TheRodDoc
December 18, 2010, 03:34 PM
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

Mizar
December 18, 2010, 03:42 PM
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

junkman_01
December 18, 2010, 03:57 PM
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.

rdstrain49
December 18, 2010, 04:22 PM
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:)

junkman_01
December 18, 2010, 05:07 PM
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.

Bluehawk
December 18, 2010, 06:58 PM
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.

ak-kev
December 18, 2010, 07:04 PM
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.

junkman_01
December 18, 2010, 07:13 PM
What are you talking about? Trying to help a guy (you included) who asks for advice and then gets arrogant about what he gets is my problem, how?:confused:

mykeal
December 18, 2010, 07:36 PM
I have never used a percussion revolver with a cylinder to forcing cone gap over 0.010 inches, that I'm aware of. I can't say that you will be dissatisfied with the performance of a gun with a 0.020 inch gap, but it's not unsafe so it won't hurt to try it out. I suspect you will find it provides at worst inconsistent group sizes; muzzle velocity will be reduced, perhaps by as much as 20% but more likely about 10%. This would not be acceptable for a target/competition gun, and I'd not use it for hunting for the same reason. For plinking and weekend target shooting it may well be ok; that rather depends on your pistol shooting abilities and expectations.

GENTLEMAN OF THE CHARCOAL
December 18, 2010, 07:54 PM
XXXX..Not worth my time and trouble..Ya'll have a good life....

BHP FAN
December 19, 2010, 12:25 AM
black powder revolvers are not modern revolvers,and the design itself is different.look at pictures of actual original percussion revolvers and check out the cylinder to barrel gap, and you'll be amazed. they were less worried about the loss of a few psi, than they were about binding up the gun from black powder fouling. If you are picky about cylinder gap, buy a Nagant revolver.

Hellgate
December 19, 2010, 02:27 AM
You will find upon firing that your hand will feel the heat of the flame out the gap on a cold day. I have fired a Remington that had the face of the cylinder out of true. i.e. as the cylinder turned the gap gradually got wider then tighter as it made its revolution. My grip hand was always much dirtier at the end of a shooting session with that gun than my other guns. No burns or anything but some sootiness.

Mizar
December 19, 2010, 04:13 AM
Gentlemen, thank you for the answers! I will definitely shoot this gun first - I always do this ;). The real problem is that i don't have another Remington with tight B/C gap to compare it to my revolver. And being my first cap and ball revolver I don't know what to expect from it.

As for my confrontation with Junkman - Mykeal, BHP FAN, Hellgate and several others did answer my question the best they can. THAT were the answers I was looking for. I clearly stated that I can do such an intervention to this gun, but all I got from Junkman was - "Live with it, you are going to break it if you try to correct it, you don't know how it operates..." When I said that I'm new to the world of black powder revolvers I didn't say that I'm new to firearms in general. When I don't know something I am not afraid to ask, even if my question may sound stupid. But I do get annoyed real fast when someone is making conclusions about my abilities without knowing me or without even seeing my work. And yes, I do get "arrogant" when somebody is trying to do the thinking instead of me.

Junkman, I am sorry for offending you.

Best,
Boris

madcratebuilder
December 19, 2010, 06:49 AM
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?

You may have a 40-60fps drop in muzzle velocity, gap well not have a major effect on accuracy. I would go shoot it and establish a base line before doing any work on it.

ironhead7544
December 19, 2010, 07:16 AM
I think a gap that big is a valid concern. I would call the maker and see if they will fix it for you. This is a common problem with revolvers. A gunsmith will remove the barrel and shorten it in a lathe enough to go in one more turn. The gap can then be set by taking some off the barrel and rethroating.

junkman_01
December 19, 2010, 08:40 AM
Boris,

All is forgiven. Best of luck with your project. :o

BHP FAN
December 19, 2010, 10:42 AM
If it were out of time [the chambers and barrel didn't line up] then I'd worry. Definately shoot it.I predict you'll find that all is well!

Mizar
December 19, 2010, 03:23 PM
Thank you, gentlemen!!!

Boris

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