Flame Cutting - Old Revolver

[Waveski]

I just received an old pre war S&W M&P. Initial impressions were excellent - finish and grips are good , screws true and not buggered , rotational lock up is very good ; end shake non-existent. Bore is clean ; no frost or pitting.

BUT , there is significant flame cutting of the top strap. I have no experience with a revolver of this age - early 1900's. How unusual/common is this condition? Should I be concerned about structural integrity?

Take a look and tell me what you think .....

 

[dvnv]

I have some well flame cut revolvers...none look like that.

I'd want to know more.

 

[John C]

My first impressions are 1) it's not that bad and 2) flame cutting is usually self limiting. I'd shoot it, with regular pressure loads. Not for structural reasons, but because parts are scarce if something does happen.

 

[Waveski]

Self limiting? My metallurgy is weak ; please expand on that.

I bought this piece as a vintage shooter ; that is why I posed the question. Would turn of the century powder have played a role? Again - the bore looks fine.

 

[silicosys4]

Oh shucks, that shallow little crease barely even extends to the sides of the top strap!

Here's how to do flame cutting right!



That's just a .357 mag, not even a maximum.

Still shoots fine though.

In your case, I would be wondering about the effects on the frame in general from having shot enough .38 loads in it to cause even that amount of cutting, more than I would the cutting itself.
K frames can handle loads that cause much more cutting than on that M&P, but those are more modern guns built as magnums.
If it locks up tight with no endshake, I would not worry about it, other than wondering why the factory cut the gas relief too far forward in the frame, since its obviously not under the forcing cone!

Self limiting means that after a certain point it will cease to continue cutting. Cutting is caused by particles from unburnt powder being blasted against your topstrap. Some loads are worse than others, faster lighter bullets seem to be worse than heavier slower bullets at causing cutting. Something to do with the timing of the bullet hitting the forcing cone in relation to the powder combustion.
In my understanding, and hopefully someone will correct me if I'm wrong, but...
Lighter bullets start moving sooner because of less inertia required for initial movement, hit the forcing cone soon enough for the still combusting powder to be blasted against the top strap as particulate matter, acting as a sandblaster....
Whereupon heavier bullets require more time to reach the forcing cone, so the powder is mostly burnt, leading to less residue blasting against the top strap, less sandblasting, less cutting. That's my understanding of the dynamics, anyways.

There is a point after which the residue does not have the velocity to continue cutting metal, and that point seems to be a 1/32" or so into the metal of the topstrap of my gun. After it has cut to that point, it will no longer continue to cut, and the cut will not grow deeper. That is what "self limiting" refers to. It will not cut through your topstrap, after a certain point the cutting will cease.
I'm guessing that because your gun is a .38 special, that cutting stopped a long time ago, and won't get any worse.

 

[W.E.G.]

That is NOT flame cutting.

That is an engineered feature known as a "FOULING CUP."
It is a deliberately dished-out area on the forward underside of the top strap.

That revolver is from an era where it was contemplated that shooters might still be shooting BLACK POWDER.

The fouling cup gives a place for the mess, that comes from shooting black powder, can accumulate without tying up the cylinder on first firing.

You must not shoot any ammunition that generates enough pressure to cause real flame-cutting in that revolver.
Stick with low-pressure ammo that is consistent with the low-pressures generated by ammo of the same era as the gun was made.

 

[Jim Watson]

W.E.G. is right, the gun was built that way.
Shoot in confidence... with standard velocity ammunition.

 

[walnut1704]

What W.E.G. said....

I'll add that flame cutting is only an issue in Magnum revolvers that have endured too much light bullet high velocity ammunition.

 

[silicosys4]

Oh shucks, he was talking about the blackpowder residue relief cut? Lol, I thought he was talking about the piddly stuff right in front of it... yea, you are right, anything that looks like true cutting on that gun is probably just lead deposits.

OP, look at post #5. That is what flame cutting looks like, and if you don't have something like that, I wouldn't worry.

 

[Waveski]

silicosys4 - That is a dandy flame cut!

W.E.G. " That is NOT flame cutting." FOULING CUP.

THANK YOU !!! So that's why it looks so machined. So that's why the action seems so good and tight - when I wrongly thought that someone had shot the bejeebers out of the revolver to cause all that "flame cutting".

Wonderful. I have a hundred year old Smith and Wesson in good working order.

As I said - I have no previous experience with a revolver this old. My 1948 Colt Official Police is modern by comparison. Fouling Cup. I love it!

This is a great forum.

 

[Old Fuff]

It's hard to tell for sure from the photograph, but it appears to be a fouling cup with a fair amount of lead splatter in it. Post the serial number on the butt and we can be more sure.

Anyway, I would be more concerned about the lead - because the bore and chambers may be misaligned and not concentric. Or it may be from shooting too soft lead bullets.

Once it is determined what's causing the leading and it's corrected it should make a fine shooter - as long as you use ammunition that's made to be safe in older revolvers. Again, a serial number should shed some light on what that would be.

 

[rcmodel]

Actual 'flame cutting' manifests itself as a straight line, directly in line with the barrel / cylinder gap.

Like this:



IMHO: Flame cutting is not actually 'flame cutting'.

If you have ever used an acetylene cutting torch, you know it takes several seconds to get the metal hot enough to start cutting it.

The nano-second the cylinder gap flame hits the top strap wouldn't even have time to warm it up, let alone cut into it.

IMHO: Flame cutting:
It is a result of powder granules blown out of the B/C gap acting as sand blast media to cut into the top strap.

It is most prevalent in Magnum calibers using large charges of slow burning ball powder.
(Almost Ideal bead blast media!)

BTW: I have never seen a (low pressure, small charge) .38 Special, .44 Special, .45 ACP, or .45 Colt revolver exhibit any sign of flame cutting, no matter how old the gun is.

Even on Army AMU K-38, .38 Spl target revolvers with years of competition & practice, and a gazillion rounds through them.

It just isn't a factor worth looking at until you get into magnum class guns.

All I see on the OP,s gun is a lot of leading.

rc

 

[joem1945]

I have a few old ones that have some dished areas by the forcing cone. I don't worry about it and shoot them.

 

[Waveski]

Fuff ; "Post the serial number on the butt and we can be more sure."

162666

38 special ; 6 1/2 " barrel , w/ lanyard ring.

 

[ColtPythonElite]

I often put a dab of heavy grease on the top strap as a barrier for flame cutting.

 

[Driftwood Johnson]

Howdy

I was away from my computer when this topic came up, so I was unable to view the OP's photo, but I had a suspicion we were talking about the Black Powder relief in the top strap.

S&W was not the only firearms manufacturer to put in such a feature, Colt did it too. It was sometimes known as the Thumbnail because of the shape.

Here is the Black Powder relief cut in a SAA made just after the turn of the Century, when Black Powder cartridges were still very much in use.







Colt was still incorporating the Black Powder cut in the top strap of this 2nd gen Colt made in 1968.





By the way, I shoot nothing but Black Powder in these two guns and determined long ago that the relief cut was useless. It never fills up with fouling. If it was not there, there would not be enough buildup of fouling at this location to cause the revolver to bind anyway. Revolvers bind from Black Powder when fouling blasted out of the barrel/cylinder gap works its way down to the cylinder pin and binds the cylinder. A well designed collet or gas ring has always prevented this from happening.

Like these:

 

[mnrivrat]

FYI

I have a Smith & Wesson Model 1899 , Model 1902, and Model 1905 guns and they all have the football shaped fouling cup on the inside of the top strap. Even my little 1903 I frame guns have them.

 

[Radagast]

Based on the serial number, its a .38 Military & Police Model of 1905 3rd Change manufactured circa 1909-1915 in the serial range 146900-241703. So probably 1909 or 1910 based on the early serial number.
Predates heat treatment of cylinders, so stick to standard pressure lead loads.

 

[Caliper_Mi]

Self limiting? My metallurgy is weak ; please expand on that.

Not really a metalurgical term at all. Self limiting here would mean that as the flame cutting starts on the top strap, the very presence of that groove causes less flame cutting to occur and that at some point the groove will be deep enough such that no further cutting happens.

I have no evidence if this is true of flame cutting or not, just explaining on the term.

 

[Waveski]

That makes perfect sense , thank you.