Colt SAA Machine Marks and Cylinder Leading?

C

conrad977

Inactive
I got back from shooting the other day and noticed what appeared to be lead on the edges of the cylinders. I can't tell if it is lead or if the bluing has been removed and I'm looking at the bare steel. I have fired this revolver on 5 different occasions and this is the first time this has happened. I fired 20 rounds of Black Hills 44 special (my first time using this brand of ammo). Is there anyway I can safely remove the lead without damaging the bluing and can I prevent this from happening in the future? The firearm is a 1979 Colt Single Action Army in 44 Special.




Also, while I had the cylinder removed, I found some markings near the forcing cone. There is a fifth mark underneath the forcing cone that cannot be seen in the picture. Any ideas?



Thanks for any input.
 
The leading is common on the face of the cylinder and the forward edges of the cylinder.

Clean. soak with Hoppe's No. 9, using a soft brush like a tooth brush and then wipe with a silicon cloth. As you shoot, regularly wipe front of cylinder and the cylinder itself. The silicon will add a measure of protection against lead depositing to the point it's hard to remove.

Same thing can and often does happen with nearly all revolvers.
 
Worse with soft lead bullets. The BH loads may have been low velocity with soft bullets. Cleans off.

The cuts look factory and may be to relieve flame cutting. S&W makes one cut in this area to allow gases to escape and not burn the frame.
 
Howdy

When you fire a cartridge, some of the high pressure gasses that push the bullet down the barrel get diverted and blast out of the barrel/cylinder gap. As the gasses exit the b/c gap, particles of carbon and vaporized lead get deposited on the front of the cylinder, in a ring shape. That is what you see, the carbon and lead that has been deposited on the face of the cylinder. Completely normal, happens to some extent with all revolvers.

You will hear various solutions to remove the rings, but the bottom line is they will return every time you fire the gun. I gave up long ago trying to remove these rings. Once you have enough revolvers, you will too.

Are the cuts in the topstrap left by the tap that threaded the frame for the barrel?
Click to expand...

Yes, that is exactly what they are. I have the same type of marks in some Rugers. Most taps have a tapered lead. When the frame is tapped for the barrel threads, the tap extends a few threads past the frame so the full profile can be cut. That is what you see, tooling marks left behind when the frame was threaded for the barrel. Notice the marks are tapered, because the front of the tap is tapered.

Years ago, many revolver makers put a relief cut on the underside of the top strap right where those marks are. The idea was, in Black Powder days, the relief cut gave the fouling some place to go so it would not bind the barrel/cylinder gap.

Here is the relief cut in a Colt Bisley from about 1906.

blackpowdertopstraprelief38-40Bisley_zps09598f22.jpg





And here is the relief cut in a 2nd Gen Colt from 1968.


blackpowdertopstraprelief2ndGenColt_zps1fa8f1f0.jpg



The relief cut never actually filled up with fouling, it really did not serve any purpose. But putting the relief cut there would have masked any tooling marks left behind from the frame tapping operation. Your 1979 Colt has no relief cut, so the tooling marks left behind by the tap are still there.

Smith and Wesson used to do the same thing, someplace I have a photo of the same type of relief cut in an old Smith.

By the way, these relief cuts do nothing to prevent flame cutting. You can see there is some flame cutting on both of these top straps.
 
The "thumbnails" on S&Ws and some Colts also allowed room for the hot gas from the b-c gap to expand and cool, reducing "flame cutting" of the top strap. Colt used it for many years. Eventually, it was found that with conventional cartridges and steel frames "flame cutting" would stop by itself before the top strap was weakened enough to be a danger. With alloy frames in hot calibers, S&W has now come up with a stainless steel shield for that area.

Jim
 
Thanks for all the replies. Tooling marks I can live with. I just wanted to make sure the gun hadn't been damaged by a previous owner.

I want to clarify that I'm not talking about the leading on the face of the cylinder. There are marks on the front edge of each cylinder chamber like the one in this picture.
 
I addressed the lead deposit, mentioning the front of the cylinder edge.

Again, it's normal with revolvers, indicating some shavings of the lead bullet.

Hoppe's No. 9 or Break Free are your friends along with a soft brush and a silicon cloth. The silicon application helps deter some of the deposits and makes it easier to to remove them.

After every cylinder or two of firing, wipe the cylinder down. This has been particularly true with the Colts I used in SASS using lead handloaded bullets.
 
Those notches are indeed to reduce flame cutting. I still believe that's what's behind the notches seen in the OP rather than unintentional chatter marks from machine tools. Any machinist who accidentally left gouges like that would be fired.
 
Those notches are indeed to reduce flame cutting. I still believe that's what's behind the notches seen in the OP rather than unintentional chatter marks from machine tools. Any machinist who accidentally left gouges like that would be fired.
Click to expand...
The marks posted about were not, "...unintentional chatter marks from machine tools...". What they said was that they were from the tap and that they were unavoidable. However, the only way I would be absolutely certain, was if I had a frame without a barrel in it and the correct tap. Then, I could screw the tap in and see if there was insufficient clearance and the marks were unavoidable. Without that, I have a tendency to believe they are tap marks inasmuch as I am very familiar with tapping in tight places. In short, with the absence of "proof", it seems logical that they are tap marks. Whereas, how a couple of notches would reduce flame cutting does not seem logical, but would likely give flame cutting a place to start.

Another way to determine if those marks are the result of a tap, is to measure the marks and compare it to the pitch of the tap. Then we could put this argument to rest.
 
IMHO, they are from the tap and they are NOT "unavoidable". The person who was running the machine allowed the tap to run too deep; that should not happen if the machine was set up correctly, but people do make mistakes. Should it have been caught in an early inspection before the frame was finished into a gun and sold? Yes. Do such mistakes happen? All the time. Is it a reason to return the gun to the factory? Owner's choice.

Jim
 
Conrad, I have a third gen .44 Spec., early eighties. Chambers were .434, barrel groove was .427. When firing any lead less than .434 I got really bad blow by, (gas cutting?). Barrel leading was excessive, and I would get the same lead you do on the outside of the cylinder. Borrowed a friend's mold that threw a .434 bullet and used those successfully for years until the owner moved on. I finally gave up on it and had itrebarreled to .45 Colt.

Anyway, you should check your chamber diameters and your barrel groove, I dont think this is an uncommon problem.
 
Gas cutting (flame cutting) is caused by the gas escaping at the barrel-cylinder gap and has almost nothing to do with bullet diameter vs cylinder mouth or barrel diameter. In fact, a tighter fit might actually increase flame cutting, though not significantly.

When any fluid is forced through a smaller space, its velocity increases, like a garden hose nozzle being closed to increase the distance the water will go. (This is why airplanes fly, but that is another story for another time.)

So the gas moving through the narrow b-c gap at high speed cuts into the top strap of the revolver. The higher pressure the load the more gas there is and the higher its velocity will be. A gun fired with moderate loads will take a long time to show gas cutting; one fired with "hot" loads will show it quickly.

There have been a number of solutions, all of which work within limits. The "thumbnail" was the first, but others have involved an inlay of erosion-resistant steel, or a shield of some kind. One solution is to increase the b-c gap; the larger the gap, the greater the area allowed for gas expansion and the less the flame cutting. But most gun owners believe that the tightest possible gap is best, so flame cutting will continue.

Jim
 
Remembering from many years ago (before Internet), the discussion in the gun rags relative to gas cutting was that it would happen and the cutting was self-limiting in that, after it cut the characteristic "groove", the progression would slow way down. I do not know if that is true, but I remember that being written. I witnessed the "cut" on two of my most high round-count guns (M58, and a Flat top .44 Blackhawk (not "Super" Blackhawk), but it never progressed to the point where the integrity of the top strap was compromised. So, the advice back then was to "just ignore it".
 
I have a 1960 S&W M/19 that leads the cylinder bevel precisely as your photo's show. Apparently the bbl leade is not quite properly cut & creates just enough interference to lead that cylinder. Owned that gun for way over 45 years & it's really no problem...just clean it & shoot it!

DAHermit: Also have an old (again 1960) flat top .44 with NO cut.....guess the practice is a sometimes thing.......I'd presume that it might be that if the threading cuts were too noticeable that the cut was done then.
 
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Great post and very informative. Whenever I have a problem or a question on any of my Single Action handguns, both Colt and Ruger, there are a few guys on this forum that I really listen to. Driftwood Johnson is one of those guys. I would clean the lead off the cylinder as many have suggested and keep on shooting.
 
Thanks for all the information guys. I'll give Hoppes a try on the cylinder. The cut marks on the frame don't bother me too much as long as they don't make the frame weaker. I've read somewhere that the quality of these early 3rd generation colts is hit or miss.
 
Hi, Dahermit,

I recall the same thing and the same advice. I think it was in an old AR in response to a member asking why the "thumbnail" had been dropped in the new guns.

Jim
 
It is a collector term for a dished out area in the top strap of a revolver above the point at which the barrel and cylinder almost meet, creating the barrel-cylinder gap. The dished out area resembles an area left by scooping with a fingernail, hence the name.

As to its purpose and pictures, see above.

Jim
 
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