Premature cylinder unlock problem, Pietta NMA

[Daniel Nighteyes]

Pards,

I have discovered a perplexing problem with one of my two still-nearly-new stainless Pietta NMA's.   Actually, I know exactly what the problem is, and what's causing it, but I haven't a clue of how to fix it.

The problem is that the cylinder bolt retracts and the cylinder rotates "backwards", out of alignment with the forcing cone, when the trigger has been tripped and the hammer is being lowered.  I'm sure it happens the same way when I fire the pistol, but it happens so fast that the cylinder doesn't have the chance to get out of alignment.  Still, this is an inherently unsafe condition that I need to fix before firing the pistol again.

By looking between cylinder bottom and frame, I can see the cylinder bolt retract almost immediately once the hammer starts moving.  My other stainless Pietta NMA, purchased at the same time (they have consecutive serial numbers), doesn't do this.

So, what to I need to do to fix this?  Is it something that I, one who is reasonably competent with tools, can repair?  Or do I need to take it to a gunsmith?

Enquiring minds wanna know, pards.

-- Nighteyes

[Professor Marvel]

Greetings Daniel -
This anomalous behaviour of your revolver is utterly perplexing to me.
Please allow me to "think on paper" as it were.
As you know, the cylinder bolt lowers because the cam on the hammer *raises* the bolt legs as the hammer is retracted. Once the tripping distance is achieved, the bolt raises to lock the cylinder due to the bolt/trigger spring pressure.  As the Hammer drops, any friction contact of the "hammer cam ramp" on the "bolt leg"  should press the bolt more firmly upward  per the falling action of the hammer.

I cannot think of any engagement by burrs or what have you on the hammer or bolt that could cause the bolt to lower.

There is however, the movement of the trigger against the bolt/trigger spring. As the trigger is pulled, there is the possibility of a burr on the side of the trigger engaging the bolt, and the direction of movement of the trigger corresponds to pulling the bolt "down".

Another possibility is if the trigger is somehow engaging both parts the of spring, taking the spring tension off the bolt which could then lower...  Possibly an ill-fitting spring?

All I can advise is disassembly, experimentation, and observation.

Aha! I suddenly perceive a possible problem - these are Stainless Steel, and as everyone knows, steel that repels rust is an Anomaly in the Universe and such Anomalies often cause reactions opposite to what is expected! If you hold the Revolver four feet above the floor and suddenly release it without looking, does it fall "down" or "up"?

yhs
Prof Marvel

[Matt Bastardson]

Have you examined all of the internal parts closely to ensure that none of them are broken (or partially broken) or so weakened that they are about to fail and no longer can perform their normal function?

I think you would begin to see this type of failing when people begin monkeying with the internal parts to try and lighten the trigger pull or hammer pull.  When you begin to lighten or thin flat springs they can begin to do all manner of weird behavior as the metal dynamics are changed.  Ditto for old worn out parts.

[Daniel Nighteyes]

I think you would begin to see this type of failing when people begin monkeying with the internal parts to try and lighten the trigger pull or hammer pull.  When you begin to lighten or thin flat springs they can begin to do all manner of weird behavior as the metal dynamics are changed.  Ditto for old worn out parts.

I bought both pistols NIB, and I haven't tinkered with 'em.

[Daniel Nighteyes]

If you hold the Revolver four feet above the floor and suddenly release it without looking, does it fall "down" or "up"?

Well, let's see......OUCH!  They fall down, Prof.

[Professor Marvel]

Well, let's see......OUCH!  They fall down, Prof.

Well sir, that at least is a good sign, that Unnatural Metal hasn't reversed naturals laws so we don;t have to send it off to Warehouse 13 .

If you remove the cylinder and play with just the trigger, does that move the bolt? If so then I suspect the bolt spring.
If NIB, can you return to vendor to make good? Else it's time for a good set of fitted screwdrivers and Pettifoggers guide :-)

If you set up a web cam, we can do a remote debugging  session just like on TV.

yhs
Prof Marvel

[Virginia Gentleman]

I would send it back to the importer for warranty work and write a letter explaining the problem and send it with the gun.

[Daniel Nighteyes]

Following Professor Marvel's suggestion I removed the cylinder and tested.  The cylinder bolt does NOT retract as it does when the cylinder is in place.

I also removed the trigger guard and inspected the trigger and bolt spring.  No observable defects.  Both appear to be properly aligned and functioning.

Replaced the cylinder but left the trigger guard off.  Put an index finger against the bolt spring while cocking and decocking the hammer.  Could definitely feel that something was pushing down on the bolt.  Removed the cylinder and tried again.  There was no sensation of anything pushing down on the bolt.  It is obvious that the hand is lightly "dragging" the cylinder back out of battery, but if the bolt were functioning properly this would not represent a problem.

My next step will be to check the hammer to see whether is it properly working against the cylinder bolt and etc.  If that ain't it, Professor Marvel, could this be the long-sought evidence of a Ghost In The Machine?  Enquiring minds want to know, for sure.

[Daniel Nighteyes]

I would send it back to the importer for warranty work and write a letter explaining the problem and send it with the gun.

I might send it back to the dealer that sold it to me -- they've got a good reputation for things like this.  Because I'd like to actually shoot it in a match or two before I start collecting Social Security, I'm not likely to send it back to Pietta.

[Matt Bastardson]

I think the next step is to get a new bolt, hand, and trigger spring, and start from scratch (i.e.replace the bolt and see if that fixes it, if not do the same for the hand, then the trigger spring.  If none of those individually fixes it, then replace pairs of parts...and if that doesn't work, replace all three.)

This sound more like a flat spring that is bent wrong or improperly tensioned.

[Professor Marvel]

My next step will be to check the hammer to see whether is it properly working against the cylinder bolt and etc.  If that ain't it, Professor Marvel, could this be the long-sought evidence of a Ghost In The Machine?  Enquiring minds want to know, for sure.

Hmmmmm  perhaps an exorcism ?

At this juncture I would suspect a broken freebamigin. Perhaps some broken bits are floating around in the frame cavity that are pushing the bolt legs up as the hammer falls...

I would want to pull all the parts and examine the hammer, bolt legs and hand under a strong light and powerful glass, as well as look into the frame innards for burrs & etc.

Daniel -this may sound like madness but if you can mark the parts so as to keep track of them you might just try swapping different pieces of the two revolvers in and out, a bit of trial and error fitting....

I always appreciated and admired levers and springs and gears and cogs and mechanical mechanisms of all kinds. This S.A. puzzle "should be" so simple and yet is is so perplexing; the timing of these things is remarkably subtle.

I recently accidentaly altered the timing of a Remmy by gently polishing the bolt ramp on the hammer. I was nearly stumped, and almost ready to use my car battery to weld more metal back on using a paper clip as a welding rod. Instead, under a strong glass I saw that the ramp was a force-fit piece of rod, and removed it with a punch. Simply by rotating the ramp a few degrees from top-dead-center when I replaced it, the lockup timing was restored.

[Professor Marvel]

Hey Daniel Did you ever fix this?
yyhs
prof marvel

[Daniel Nighteyes]

Hey Daniel Did you ever fix this?
yyhs
prof marvel

Not yet.  I've had to put my shooting on the back burner for a while, so I've not even taken the pistol in question out of the safe.