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1851 Navy Cylinder Gap

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ahedgpe

32 Cal
Joined
Mar 15, 2021
Messages
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One of my kids has a brass frame Pietta 1851 .44cal that is at .015" cylinder gap. I never thought to measure it before, but checked today. I measured with the hammer at full cock and cylinder pulled back. In searching, I saw everything from .004 - .020" as being acceptable (.020" was debatable). I also verified that there were no cylinder imprints on the frame and the pistol has good lockup. It has never had heavy loads in it, always been around 18-20gr loads (I make their powder loads for them). Is this acceptable cylinder gap?
 
I feel anything over .010 needs addressed. The hand has to reach for the ratchet teeth as it is pushed forward at each turn and the cylinder gets a run at the frame at discharge to increase imprinting risk.
 
I feel anything over .010 needs addressed. The hand has to reach for the ratchet teeth as it is pushed forward at each turn and the cylinder gets a run at the frame at discharge to increase imprinting risk.

I've been reading a ton of posts about cylinder gap and looked through Pettifogger's files on tuning both the Pietta and Uberti. I removed the barrel and cylinder, fully reinstalled/seated the barrel and turned it 180 degrees, and the arbor and frame line up perfectly, just like Pettifogger's pic (attached). With that being the case, I'm not quite sure I understand what would need to be done to correct too much cylinder gap. Below is a pic of the pistol with hammer fully cocked and cylinder pulled back.
 

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To correct that much gap remove the two alignment pins and mill off the face of the frame. The amount depends on how close you want the gap, I like .003” gap. Then the end of the arbor can be drilled and tapped for a set screw to adjust wedge fit.
 
That cylinder gap is excessive in my opinion and also the reason all my cap and ball revolvers are steel frame. I do think the brass alloy used these days is stronger than it used to be back in the 1960s, but if I want to shoot mousy loads I have steel frame pocket models for that. My suggestion would be to buy one of the steel frames that are sometimes sold separately.
 
To correct that much gap remove the two alignment pins and mill off the face of the frame. The amount depends on how close you want the gap, I like .003” gap. Then the end of the arbor can be drilled and tapped for a set screw to adjust wedge fit.

Would it be better to mill the barrel side, instead of the frame, since the alignment pins might be damaged while removing them?
 
The pins that I have removed came out OK but I don’t use cheap pliers. If you do damage a pin a replacement would be simple to make. To cut metal from the barrel I’d mount it between centers on the lathe to machine it. Be careful with an interrupted cut.
 
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The pins that I have removed came out OK but I don’t use cheap pliers. If you do damage a pin a replacement would be simple to make. To cut metal from the barrel I’d mount it between centers on the lathe to machine it. Be careful with an interrupted cut.

Thanks for that info. It would seem that if I remove metal from the barrel or frame, that I would potentially need to remove metal from the end of the arbor (depending on fit of the arbor in the hole). Is this accurate?
 
Would it be better to mill the barrel side, instead of the frame, since the alignment pins might be damaged while removing them?
That is what I prefer to do as the barrel can be set up on centers in the lathe and the barrel lug is reduced square with the bore. It is necessary to take light cuts so as not to torque the lug out of alignment. This also precludes having to remove the lug pin. The lathe set up to cut the barrel lug back is much easier than the mill set up to cut the frame back. Some times the pin holes need to be made deeper by the amount removed from the lug but not always.
 
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When pulling lug pins I like to put some mild steel vice jaw liners in my Wilton , clamp onto each pin individually and pull the frame away from the pin. Gives better grip and leverage , it also saves the pins.
 
Thanks for that info. It would seem that if I remove metal from the barrel or frame, that I would potentially need to remove metal from the end of the arbor (depending on fit of the arbor in the hole). Is this accurate?
Yes the arbor fit will need to be checked.
The barrel machining is more difficult to do so that’s why I machine the frame. Strip the frame and clamp the back surface to the table and the cut can be done easily with accuracy. The crank shaft effect of turning the barrel makes me nervous. Barrels if available are currently listed at $125 plus shipping.
 
I am old school, so correct me if I am wrong. A vise can be set up with two pieces of squared steel and the barrel lug placed between them, using a feeler gauge to only allow the lug to protrude a couple of thousandths beyond the backing pieces. A file can be used to trim the lug down to the proper length.

I know this is not rocket surgery but it has worked for me in the past.

Regards,

Jim
 
I am old school, so correct me if I am wrong. A vise can be set up with two pieces of squared steel and the barrel lug placed between them, using a feeler gauge to only allow the lug to protrude a couple of thousandths beyond the backing pieces. A file can be used to trim the lug down to the proper length.

I know this is not rocket surgery but it has worked for me in the past.

Regards,

Jim

I'm on the same page with this. I have used this method when cutting down a shotgun barrel to get a straight cut.
 
Yup, works fine if your good with a file and marking fluid, I am a file junky, can't have enough of them, but it is much faster and usually more accurate done in my lathe or mill.
Working a file correctly is an art from in it's own right and I'm still leaning how after a life time of use.
 
If the pistol was mine and it only had a .015 cylinder/barrel gap I would leave it alone and shoot it.

The .015 gap will send a little more fire/flame out the sides and slightly lower the velocity of the ball but in the end, there won't be any difference worth noting. The gun will shoot fine as it is.
 
Well, a little project work tonight on it. I remove just a little metal from the bottom of the barrel side and a little off the arbor. Measured the cylinder gap at .08 now. Ordered a new barrel wedge as this one was well worn. Considering the set screw idea on the end of the arbor as a way to keep everything semi tight with the wedge.
 
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I am old school, so correct me if I am wrong. A vise can be set up with two pieces of squared steel and the barrel lug placed between them, using a feeler gauge to only allow the lug to protrude a couple of thousandths beyond the backing pieces. A file can be used to trim the lug down to the proper length.

I know this is not rocket surgery but it has worked for me in the past.

Regards,

Jim
Even though I have a lathe and a milling machine, this is how I healed my ‘51. Job was done, properly, before I could have set up either machine. I used a 10” single cut file, cleaned and chalked.
 
I couldn't help myself, I drilled/tapped the front of the arbor and installed a set screw. Worked for a couple hours just taking my time to get the set screw filed down to the right fit in the arbor key hole and just barely protruding out the front of the arbor (arbor sits almost flush in hole). Results are a nice tight fit with .07" gap. The wedge is tight, so I might work on the fitment a bit more. It can not be moved without tapping with a mallet.
 
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