Pietta revolver problem.....???

[Brad Foust]

Got a 36 cal model 1851 Pietta revolver that had broken spring on the hand.
Got a replacement and installed simple enough.
BUT now the gun will not full cock when all assembled.
When I take the barrel and cylinder off it full cocks and everything else like it should.
Any ideas what could be the problem??
I dont wanna just go off half cocked and start filing, etc???
Thanks

 

[curator]

Bigmon: Did you replace the entire hand or just the hand spring? A new hand will need to be fitted to work properly. It sounds like it is a bit too long and the cylinder bolt is locking before the hammer reaches full cock. If you are not familiar with adjusting the "timing" on single action revolvers, you may need the services of a good gunsmith.

 

[Zonie]

Curator hit the nail on the head.

As you cock the gun, the tip of the hand is rotating the cylinder. The further the hammer is cocked, the further the hand tries to rotate the cylinder.

When the notches in the cylinder get close to the right place, the cylinder bolt or stop clicks up into place locking the cylinder in that position.

If the hammer is not at full cock when this happens, any further attempt to bring it further back raises the hand further.

Because the cylinder is locked in position, the hand can't move it so, the hammer can't reach full cock.

Carefully stoning** off a little material from the end of the hand will fix the problem.

The concern here is, if you remove too much from the end of the hand, it won't be long enough to turn the cylinder to the position it needs to be in for the cylinder bolt (stop) to lock it in place.

IMO, most people who can take apart and reassemble a C & B revolver are capable of fixing the problem.

I suggest you strip the gun down to the point that the only things that are installed is the hammer and the hand, the cylinder bolt and trigger and the flat spring*** along with the cylinder and the barrel. Leave the mainspring away from the bottom of the hammer or removed from the grip strap. It is not needed at this time.

With the hand out of the gun, notice the angle of the end that pushes against the ratchet on the rear of the cylinder.

Keeping this surface on the hand parallel with the surface of a flat whet stone, take a few swipes to remove a little material. Then reassemble the hand, hammer, cylinder bolt, trigger, bolt and trigger spring, cylinder and barrel and try cocking the hammer. Do not force it.

If it doesn't cock, take everything except for the cylinder and the barrel back apart and lightly grind a bit more off of the end of the hand.

Repeat this until the cylinder is locked in place and the hammer reaches the full cocked position.
You should try cocking the pistol so that every chamber gets aligned with the barrel once things seem to be working right.
Don't be surprised if things work nicely with several chambers aligned with the barrel but a few still cause a hang up. That is due to some wear or machining tolerances on the cylinder ratchet teeth.
If there is still some hang up, continue to adjust the length of the hand until all of the chambers align with the barrel and lock in place.

You can quit here but if it were me, I would remove the hand and take just a few strokes to remove a tiny bit more from the end.

Once this was done, I would totally reassemble the gun, congratulate myself and sit back with something cool to drink.

** I mention stoning with a whet stone because it works slowly and leaves a good finish on the end of the hand.
A small, very fine tooth flat file can also be used but it will often leave a rough surface.
Files also can remove a lot of material fast so using one can result in the hand becoming too short before the damage is noticed.

*** The flat cylinder bolt/trigger spring can be installed two ways. If it is not installed the right way, the cylinder bolt and trigger won't work.
If this happens, turn the spring over and reinstall it. Also notice which end of the springs leaves is pushing on the trigger so you always install it correctly.

 

[denster]

Zonie gave a good description of how to accomplish the fix. One thing I would add is that if the pistol worked fine prior to the hand spring breaking you can use the old hand as a gauge to fit the new one. If you need to remove more than a few thousandths then a file is the tool to start and finish with a stone in the manner Zonie described.

 

[Brad Foust]

Thanks friends for the knowledgable advice.
I had figured that the hand was too long but didnt want to experiment.
I would have compared it to the original hand length but my friend who owns the pistol didnt bring it back with him.
It took two tries but now the gun functions correctly, we even went out and fired a couple cylinders.
I used a fine file and slowly and closly kept the shape of the tip of the hand.
My only question now is, should that end of the hand be hardened??
Might be hard to do with the spring attached, without ruining the spring temper??
Thanks again

 

[denster]

The hand should not be hardened. It is what is known as a wear part. ie: The part it interacts with is the cylinder and is expensive vs the hand which is inexpensive. In any case with even heavy use the hand will last a long long time.

 

[Brad Foust]

Thanks to all on this subject.
It is now functioning well.
I'll consider this subject solved and move on to another.
Regards to all

 

[M. De Land]

Good job guys describing hand adjustment.
I will make a few related comments concerning the topic.
First of all hands are not dead soft and I would be very surprised if there is 5 points of Rockwell hardness difference between the hand and cylinder ratchet star having file, stoned and adjusted both.
The main reason the hand nose wears back first is because it has five to six times the contact wear (one hand nose, five to six ratchet teeth). compared to each tooth. The contact surface area of both is nearly identical, one the inverse of the other.
The hand nose revolves around a portion of the ratchet tooth in the lift by the changing arc radius of the cylinder. At the top of the stroke it should start to pass by now becoming a cam rather than a lift lever alone. This is not true of double notch hands as the second notch will carry up to lock up.
This is the reason hand width is important, especially in single contact hands.
I do not agree that a tight tooth/ratchet nose contact should just be left alone. The tooth should be fit to the hand nose that works smoothly on all other chambers. The carry up to bolt lock should feel the same on all chambers and the hammer should move a bit farther to the rear after lock up.
A tight tooth will quickly raise a burr or show a peen area to identify it. This area should be filed , then stoned to match the carry up pressure on all the other chambers.
This is my understanding to this point in the continual evolution of things to be learned in revolver-craft.

 

[M. De Land]

The trouble with leaving a tight tooth/hand contact on one chamber is that it will likely make the hand short on the one with the least lift rise.
This is one of the reasons for the thumb drag test which will reveal a short lift chamber.
I think this is brought about by not fitting the ratchet teeth to the hand length that works smoothly on the majority of the other chambers.
IF they all feel the same in the lift and pass the thumb drag test than the adjustment will maximize the life of all related parts.

 

[denster]

I believe you misunderstood my statement regarding the hand being a wear part. You are correct stating there is not much difference in the hardness of the steel between hand and cylinder. Both being a mild steel. You are also correct in stating that the differential of wear to the hand vs cylinder is due to the multiple teeth the hand contacts as well as how the hand contacts the teeth. This would all change were you to make the hand from high carbon steel and harden it or case harden the mild steel hand. Doing so would shift the majority of wear to the cylinder ratchet. That was my point.

 

[M. De Land]

I understood your point and was just adding some thoughts on the topic.
Many people think a hand is dead soft and the ratchet star much harder. Actually they both have the characteristic of being more tough than hard although both have some hardness present if made correctly.
I am always impressed that they last anytime at all with the amount of pressure put on such small contact surfaces.

 

[AZbpBurner]

Dad brought home an Uberti-made 1861 Colt Navy in 1968, when I was still in High School. It was my job to disassemble, clean & reassemble. We fired it a lot over the years, and when I was out on my own, Dad continued using it up into the 80's. He finally packed it away when he had to give the hammer extra force when cocking it in order to get the cylinder to advance enough to lock up. He gave it to me several years ago. A new hand was fitted & it now functions as-new.

As I recall, Dad used either a fine 3-in-1 type oil or else Birchwood Casey Synthetic oil on all his locks and revolvers. It took about 20 years of hard use and thousands of rounds fired to wear a properly (lightly) lubed hand. Fitting a replacement was a simple task.