[GhostJim]

I am new to the forum, but I am hoping I that I might be able to get some help on a Python Elite that belonged to my father. The firearm was purchased about 2000 and hasn't had too many rounds put through it (maybe a few hundred). The lock up seems perfect and I have no other issues, however after reading on this forum that the cylinder gap should be no more that .008" and the total end shake .003" i decided to get a set of feeler gauges and measure. I find that the gap ends up varying depending on the chamber from .008" to .010" and the resulting end shake from .002" to .004". Any thoughts on why it would be out of spec, and what are my options with this firearm? I hadn't planned to shoot it a lot, but I hate the idea of not being able to shoot it at all. Any help would be greatly appreciated.

 

[sturmgewehr]

Pretty big numbers IMHO. I’ve not owned later production Pythons but would not be surprised that QC would fall off
to that degree. My 1972 B/C gap Measures .0045 with no end shake at all.

 

[Olle]

The specs you have read are more than likely from Kuhnhausen's manual, and I'm not sure if I have ever seen any actual Colt specs on this. However, I have seen a lot of Pythons with gaps not ever close to the numbers you see in manuals and on the forum, which tells me that Colt's specs were not nearly as strict as, for example, Kuhnhausen's. The fact that Colt's workers often used a file instead of a facing tool to adjust the gap tells me that they didn't pay as much attention to the gap as a performance oriented gunsmith would.

The Elite is a later model where the end shake is a bit complicated to adjust, as it requires some skilled lathe work. Adjusting the barrel gap is also a job for a qualified machinist/gunsmith, and I figure the whole job would set you back at least $400. The good news is that the revolver is perfectly safe to fire, it's not like it will blow up in your face or anything like that. All you'll see is a slight loss of accuracy, probably so minute that you won't notice a thing.

 

[bsmalley23]

The specs you have read are more than likely from Kuhnhausen's manual, and I'm not sure if I have ever seen any actual Colt specs on this. However, I have seen a lot of Pythons with gaps not ever close to the numbers you see in manuals and on the forum, which tells me that Colt's specs were not nearly as strict as, for example, Kuhnhausen's. The fact that Colt's workers often used a file instead of a facing tool to adjust the gap tells me that they didn't pay as much attention to the gap as a performance oriented gunsmith would.

The Elite is a later model where the end shake is a bit complicated to adjust, as it requires some skilled lathe work. Adjusting the barrel gap is also a job for a qualified machinist/gunsmith, and I figure the whole job would set you back at least $400. The good news is that the revolver is perfectly safe to fire, it's not like it will blow up in your face or anything like that. All you'll see is a slight loss of accuracy, probably so minute that you won't notice a thing.

I believe the shop manual specs are actual factory specs as they were intended at the beginning of production. However, finding a gun adhering to those specs may be about impossible, especially the peak into strike production of the late '70s through '80s.

I wouldn't worry about the b/c gap. Factory max is .008" but being wider will not hurt anything except a loss of FPS. My 1972 which was in original factory condition has a .008" gap, and the forcing cone face was finished with a file instead of facing reamer. I would prefer a .004" b/c gap, but .008" doesn't affect anything for me. It's not a big enough deal to warrant barrel removal, set-back, and re-cutting of the cone. Absolutely no endshake in this gun.

I would worry about the endshake. I think the factory spec on that is .003", but my standard is ZERO, especially on later guns with the newer cylinder assembly, as they need professional repaired when endshake is bad enough. Also considering the price of used Pythons, who wants to pay $2K for a gun with endshake that requires a skilled machinist to repair? The earlier style can be shimmed for minor endshake.

The reason I hate any endshake is because any movement allows front to rear motion of the cylinder which will act like a peen with every shot fired. The hotter the shots, the faster the tolerance will open up. It's just an ongoing problem that only gets worse, not better.

 

[nsege]

I have a 1952 Officer's Special with some .005 endshake. Where does one go about finding a shim referenced above? All I've ever seen/used are for Smith & Wessons. I did see a post on here I believe from a fellow that describes how to make one, but I have neither the machinery or skills to make my own.

 

[mizzouhunter]

Check with Ron Powers from Power Custom about endshake shims, I had to have my barrel setback by Cylinder and Slide, but that was after several thousand rounds.

 

[nsege]

Power custom is what I've used for S&W's, but they don't list anything for Colts.

 

[Olle]

Check with Ron Powers from Power Custom about endshake shims, I had to have my barrel setback by Cylinder and Slide, but that was after several thousand rounds.

You can't shim the cylinders on the late style Pythons, you have to replace the cylinder bushing. It's not a separate part, so it has to be cut out, and a new one needs to be made. This is not a complicated operation if you are a skilled machinist, but it's still a job that takes some time and precision turning to do (=$$)

 

[dfariswheel]

Most older Colt and S&W revolver specs were for a barrel-cylinder gap of from 0.004" to 0.008" with 0.005" being considered as about perfect.
In fact, that holds for any revolver of most any brand or type. A barrel-cylinder gap is a barrel-cylinder gap and subject to the same forces.
These days S&W says that 0.012" is "in spec".
So, if your Python is at 0.008" it's in spec and good to go, just not as "perfect" as you might want.

The cylinder end shake is problematic. Factory spec was for a maximum of 0.003".
When it gets over that the cylinder sliding back and forth when fired literally hammers the gun to death if allowed to remain un-repaired.
The movement allows the cylinder to become a hammer that will batter the frame both under the barrel and the breech face, the ejector, the cylinder collar, and if bad enough; the rear of the barrel.
The battering can leave impact peening damage of the ejector on the frame that can require machining to remove and fitting of a new ejector.

The problem is, Colt no longer services revolvers and Colt was about the only company that had the special hydraulic device used to stretch the cylinder collar.
These days the repair requires machining off the collar and press fitting a newly made separate collar.

Due to the high prices of Pythons these days I'd be looking at getting whatever repair was needed to correct the end shake, or just shoot it with only very light .38 Special loads, and not many of them. In other words, I'd basically retire the gun.
Not getting it repaired is like owning a Ferrari you can't drive.

I don't know what repair method he uses but Master pistolsmith Frank Glenn can repair the end shake, and if it was my Python I'd be talking to him before I shot it any more.

Frank Glenn-Glenn Custom Complete Gunsmithing Service Glendale AZ

 

[650931]

Well, a tiny amount of endshake is preferred, as this gentleman covered in his post. He explains why:

“I used to be a hardcore fanatic about the wonders of 0 endshake. One theme running throughout our story is that 0 endshake is not the wondrous nirvana state that a gun *user* tends to assume but rather is a very brittle state that takes any existing imperfections the revolver has and multiplies it by a non trivial amount.

In order to have near 0 endshake, you need a collar that positions the cylinder right against the rear of the frame and prevents all forward motion (or more aggressively: pushing against the rear). At least two problems explode out of this situation. First, if any two contact surfaces are rough, they will be pressed tightly against each other, with obvious consequences. Second, if the cylinder cannot move forward, then as it rotates, if it encounters any resistance it must be forced straight through it. With some play the cylinder can often work around such things. The practical result? For each of the guns where we set endshake to near 0 there was a substantial epilogue of playing "why is the revolver binding and how to fix it?" that took longer, generally, than doing the dramatic surgery of shoving a bushing into the core of the cylinder.”



Colt V-spring Adventures: Trip report: Frank Glenn gunsmithing lessons

My personal advice to you, is to simply call Frank, explain what you have, what its doing, and ask him what his recommendation is.

 

[Olle]

That makes perfect sense, and that's why I'm not too worried about it. The Python cylinder assemblies are seldom perfectly straight and true (which becomes evident when you measure the barrel gap on each chamber) so zero endshake is difficult to accomplish without inducing friction. There also machining marks you have to take into account, so if you fit a cylinder to zero endshake you will have two slightly rough surfaces rubbing against each other. It would be different if the surfaces were polished, perfectly true and parallel with each other, but they're not. A revolver is basically a machine, and if you build a machine without bearings you don't need to tighten up the tolerances too much.

 

[GhostJim]

Thank you everyone for the info. I E-mailed Frank Glenn however he simply mentioned possible lead spitting at a BC gap of .008, this is not something I have noticed although I am not sure I would during normal shooting. He also mentioned measuring the BC gap with the maximum feeler gauge that will allow dry firing all six chambers. 2 of the chambers measured .009 BC gap with .003 endshake, 1 chamber was tighter with .008 BC gap and .002 end shake, and 2 measured at .010 with .004 end shake. So if I understand correctly does that put the BC gap and therefore the resulting end shake at the smaller measurement and therefore within spec? He also mention holding the cylinder back and measuring headspace. I am confused by his reply and the difference between BC gap and headspace. Either way my current plant is to continue to occasionally fire it using mostly .38s and maybe the occasional cylinder of light 357 and just keep an eye on the measurements to see if it gets worse.

 

[dfariswheel]

Barrel-cylinder gap is just that.

Head space is at the rear of the cylinder.
That's the space between the frame breech face and the cartridge case head.

All of this has to be taken into effect when building or inspecting a revolver. Head space only gets bigger when the cylinder develops cylinder end shake.
Wear or battering allows the cylinder to move forward. When it moves forward the head space opens up.
Correcting end shake also corrects head space unless the gun was defective from the factory or something is wrong.

One reason for varying barrel-cylinder gap is if the cylinder crane is sprung, or bent. That causes the cylinder to "wobble" and the gap will open and close.
Cranes usually get bent by someone flipping the cylinder open and shut with a flick of the wrist, sometimes known as "Bogarting" the gun, ala Humphrey Bogart.

If you send the gun to Glenn he'll check all this out and correct it back to factory standards and specs..

 

[GhostJim]

I guess I have one more question. All of these measurements were taken while the action was at rest, which is the method I saw described in a previous post. On a Python however, when the trigger is at the rear most position during firing, the cylinder will be at full "bank vault" lock up, with the second notch of the hand engaging the cylinder. Since there is no movement at the point of firing, how would the cylinder "hammer" the frame of the firearm, and why would the measurements at rest even matter? What am I missing?

 

[dfariswheel]

The cylinder is tightly locked from ROTATION, but firing energy will push the cylinder both forward and back.
This is Newton's Law in action; "For every action there's an equal but opposite reaction".

First the cylinder moves forward as the firing pin strikes and the gun begins to recoil. The cylinder attempts to remain still while the frame moves to the rear. The frame impacts the cylinder at the front.
Then the cylinder moves to the rear pushed by the bullet moving forward and the cylinder impacts the frame at the rear.
Then the cylinder just bounces back and forth inside the frame until the energy is dissipated and the cylinder comes to rest.

Measurements are taken with the action at rest because when cocked there is some spring pressure in the action that can cause false readings.

 

[porsche]

If it were mine with those numbers I would retire it or send off for repair. Long run it will be economical to fix before more wear is seen.

 

[GhostJim]

The cylinder is tightly locked from ROTATION, but firing energy will push the cylinder both forward and back.
This is Newton's Law in action; "For every action there's an equal but opposite reaction".

First the cylinder moves forward as the firing pin strikes and the gun begins to recoil. The cylinder attempts to remain still while the frame moves to the rear. The frame impacts the cylinder at the front.
Then the cylinder moves to the rear pushed by the bullet moving forward and the cylinder impacts the frame at the rear.
Then the cylinder just bounces back and forth inside the frame until the energy is dissipated and the cylinder comes to rest.

Measurements are taken with the action at rest because when cocked there is some spring pressure in the action that can cause false readings.

I can see how this would be the case with other revolvers, but I am still confused as to how this would happen in a properly timed Python because of Colt's unique action. When my Python is at full lockup, (with the trigger all the way to the rear), I cannot physically create any movement in the cylinder. Not with either forward or rearward pressure because of the lock up created by the hand. I am of course not exerting extreme pressures on the firearm, but the hand does not release the cylinder until the trigger is released and the action is returned to rest. Perhaps a better explanation than what I am giving - "In this action, the hand that rotates the cylinder pushes the cylinder into a tight lock-up and holds it there under pressure. The harder the trigger is pulled (within reason) the tighter the cylinder is locked in place."
It's this lock up, under pressure, and at the time of ignition that should not allow any movement throughout the recoil process. All forces exerted on the cylinder would be absorbed by the hand which would be preventing any movement. In order to move the cylinder at full lockup the hand would have to physically move, which would cause trigger slap or damage the hand. It is this lock up that any Python owner should be able to reproduce by holding the trigger to the rear and exerting pressures on the cylinder. A properly timed Python should have no rotation or movement.

 

[GhostJim]

Upon further inspection I believe I am wrong about trigger slap. I can open the cylinder and push the hand back independently without any interaction on the pulled trigger. However with the gun at full lock up there is no movement in my cylinder whatsoever. I would also like to note that my theory on the lock up of the Python at the time of ignition seems to match with the method Frank Glenn described in his E-mail for measuring BC GAP. He stated that it needed to be the largest size feeler that would dry fire on all six chambers. Dry firing would mean full lock up, and I feel that unless there is something I am missing, this would mean that full lock up is the measurement that matters. Which again, on a properly timed Python, that should be zero movement and according to Frank Glenn a BC gap of .008 or less to prevent lead spitting.

 

[Olle]

The cylinder is tightly locked from ROTATION, but firing energy will push the cylinder both forward and back.
This is Newton's Law in action; "For every action there's an equal but opposite reaction".

First the cylinder moves forward as the firing pin strikes and the gun begins to recoil. The cylinder attempts to remain still while the frame moves to the rear. The frame impacts the cylinder at the front.
Then the cylinder moves to the rear pushed by the bullet moving forward and the cylinder impacts the frame at the rear.
Then the cylinder just bounces back and forth inside the frame until the energy is dissipated and the cylinder comes to rest.

Measurements are taken with the action at rest because when cocked there is some spring pressure in the action that can cause false readings.

I have tried to wrap my head around this in the past, and I believe it could actually start with the cylinder moving to the rear. The cartridge expands when the cartridge is ignited, and this would make it stick to the chamber and pull the cylinder to the rear before the bullet exits. Once the pressure drops, the cartridge comes loose again and is free to bounce back and forth with the rest of the parts.

Not that it matters much, it's just one of those things that keep me up at night.

 

[dfariswheel]

There's a difference between manually trying to move the cylinder back and forth, and firing a live cartridge.
The cartridge pressure will move things around, and while not being into physics, I'd imagine the frame itself flexes slightly, making room for the cylinder to move.

As for which way the cylinder moves.........
The first force that acts on the cylinder is the impact of the firing pin on the cartridge, which drives the cylinder forward.
When the cartridge fires the force would push the cylinder to the rear, but I think that what actually happens is the rearward thrust of the cartridge against the frame causes the frame to move rearward while Newton causes the cylinder to attempt to remain stationary.
After that everything is bouncing around like a rubber ball.