Its back untouched, cylinder problem

[Tom-ADC]

Okay the shop has had this gun for months and done nothing, a Pietta SA 1873 clone in 45LC, it has a problem when shooting that after a few rounds it locks up and cylinder won't turn.
Where should I start checking?
And yes I'm just a tad:-x

[Tom-ADC]

Update I just put a set of snap caps in it and I can't fire on all six without the cylinder getting tighter and tighter until it locks up.:confused:

[Geraldo]

Does it always get tight on the same chamber or chambers? If so, the rear face of the cylinder may need trued up in a lathe.

[oneokie]

Have you checked to see if the base pin hole is square with the front and rear faces of the cylinder?

[skeet1]

I think your clearance between the end of your barrel and your cylinder is to close. When the gun heats up when firing the gap clearance closes up. If this is the problem it is easy to fix.

Ken

[Dan Cash]

+1 for the cylinder face not being square. That combined with a close cylinder/barrel gap will take very little fouling to lock the gun. Find a machinist to check the cylinder and while at it, check both ends. The machinist need not be a gunsmith and the check will take only a few minutes. You want to know if the ends of the cylinder are square with the base pin hole.

[slim1836]

Ought to be able to check end gap with a set of automotive feeler gauges.

[Tom-ADC]

I can see almost no light between the cylinder and barrel I'll feeler gage them tomorrow BUT it locked up today dry firing using snap caps? Whats up with that?

[Tom-ADC]

Have you checked to see if the base pin hole is square with the front and rear faces of the cylinder?

Pin slides in and out okay, seems to go straight in?

[Tom-ADC]

I can feel the cylinder dragging on the back of the barrel on at least one chamber and maybe two cylindwer is a very tight fit.
Any thoughts on just draw filing a tick off the barrel? Bet it wouldn;t take more then a couple of strokes?

[mroliver77]

You need to make sure it is perfectly clean. Check the area that cylinder runs against front and rear for burrs etc. Then check to see if it free spins freely. Check for end play(front and back) movement of the cyl. There should be a couple thou. Check the clearance with the feeler gauges. If this all checks out look at the hand and ratchet surfaces for signs of odd wear or something not right. If this all checks again load the snap caps and try to cycle. With every step look, feel think about it and understand what is going on. If none of this works, find a way to check for squareness of the pin to face and pin to frame etc. These guns are very simple machines and should be straightforward to diagnose.
Jay

[Tom-ADC]

Jay will do but this gun has done this from the first time I shot it. I doubt a total of 12 rounds has been thru it and zero BP. Basically a new gun except its maybe 6-7 years old I did buy it new.

[waksupi]

I can feel the cylinder dragging on the back of the barrel on at least one chamber and maybe two cylindwer is a very tight fit.
Any thoughts on just draw filing a tick off the barrel? Bet it wouldn;t take more then a couple of strokes?

I wouldn't do that. If I thought it needed shortening, I would have a machinist do it in a lathe. Better yet, send it back, and make the factory do it right.

[John Taylor]

Cylinder gap to barrel should be .006". If it is hanging up in the same place then the cylinder is not true.

[Tom-ADC]

I can get a .0015 feeler gage between all cylinders and barrel but I can also fit a .0025 between 4 of them. So the clearance is super tight.

[oneokie]

Pin slides in and out okay, seems to go straight in?

This has nothing to do with your problem.

Either the cylinder face is not square with the base pin bore, or the front face of the cylinder has been mis machined.

Did you also check clearance between the recoil boss and the flat surface of the ratchet?

A simple way to check is to clamp the head of the base pin in something solid so you can rotate the cylinder on the base pin. Rig up some kind of indicator that is also mounted solid and set the indicator so that it will show different clearances between the tip of the indicator and the front face of the cylinder.

Mark the high and low side of the front face of the cylinder. Reverse the position of the cylinder on the base pin and check the rear face of the cylinder.
Mark these high and low places also.

If the high on one end of the cylinder matches the low on the other end, the base pin bore is not square with the faces of the cylinder.

As someone else suggested, send it back to the factory.

[S.R.Custom]

I can get a .0015 feeler gage between all cylinders and barrel but I can also fit a .0025 between 4 of them. So the clearance is super tight.

.001" wobble from one side of the cylinder to the other is not bad. Don't worry about the cylinder. I'd focus my attention on what does and does not affect the clearance at the end of the barrel...

Between the feeler gauge, marks on the end of the barrel, and holding the gun to the light, you should be able to see the 'high' spot on the end of the barrel. (They're rarely cut absolutely square.) With the gun held in a padded vice --a folded towel will suffice-- hit the high spot with a fine file. Just take off .001" until you get to .006" or sufficient clearance, whichever is less. Go slow, be patient, and you'll be fine.

However, if you take off .002" or so and see no improvement, stop. Your problem could be excessive end-shake (fore/aft cylinder play). Without having the gun in front of me, it would be impossible for me to say definitively what the problem is, so if a little light file work doesn't do the trick, take it to a trusted local 'smith.

Very seldom does one get satisfaction sending the Italian made stuff back to the "factory." The factory is in Italy, and they are NOT sending your gun back there for repair. Rather, when the importer/distributor gets it, they have "technicians" who, more often than not, screw it up worse. If they do anything at all.

[Tom-ADC]

Here are the last 5 cases I fired in the gun, do the primer strikes look off center?
When these are in the cylinder the fireing pin hit is at 6 o'clock.

http://pic20.picturetrail.com/VOL174/1021972/3058943/396365769.jpg

[John Taylor]

It would be nice to see them in the center but what you have is not that uncommon. Looks like the hammer blow is quite sufficient, might be able to take some off the main spring and have a better trigger pull.

[Char-Gar]

My money is on the barrel/cylinder gap being too small. The front of the cylinder is also about .001 from being dead straight accross. Open the gap to about .004 and the problem should go away.

I woulnt do it with a file. Brownell makes some tools just to do this and keep the barrel root square in the process.

[Tom-ADC]

Okay I'm a redneck but I took a sheet of window glass, some 320 wet & dry and kerosene and doing figure 8's I took the cylinder face down until I have .005 clearance. The gun no longer locks up with the snap caps, but now that I can actually see a gap between the cylinder and barrel I swear the back of the barrel isn't square looks to be more of a gap at the top then the bottom. I'll shoot it next week and see how that goes. I think I now know why these were so cheap when I bought it.

[Char-Gar]

Good for you. The glass and 320 paper is a very good idea. Don't worry about the barrel root and cylinder not being 100% square. You will never notice it in shooting.

[Tom-ADC]

We'll know in a couple of days, looking forward to a range trip.

[StrawHat]

I have always regarded the Italian C&B clones as being kit guns, I did not know it extended to the cartridge revolvers also. The good news is they are easy to work on and home done repairs are usually inexpensive. Glad you were able to get it up and running. Good luck at the range.