Frame stretch

[Richard93]

HI,
I'm new to the forum and I don't know if this is the right section.
I have a 629 used with magnum loads and light loads. Looking at the frames there seems to be some marks. They told me it's normal because the frame stretches over time. Have any of you ever seen something like this?

 

[GnarlsR2]

Steel is known to have “elasticity”.

It will stretch under load but returns to its size.

If it’s stretched under a load that is beyond its elasticity limit, it may be permanently deformed.

There is also “thermal expansion” in steel, but returns to its size after cooling. Steel will also “shrink” when subjected to freezing temperatures. I put the bearing caps in the freezer and warmed up the U-joints in the oven to make it way easier to install the bearing caps in a U-joint for my driveshafts.

I would think firearms have been manufactured for so many years that whatever metal is used that stretching or deformation would not be an issue for reliability or longevity.

 

[Capt. F.]

Good morning Richard,
Frame stretch has been talked about in other postings but it appears this happens in older guns with softer metals, especially top break Smiths.
I’m sure more knowledgeable folks than me will be along to answer your question.

 

[stansdds]

Welcome to the S&W Forums. Are you positive that this is not just less than stellar factory machining of the frame?

 

[Richard93]

Thanks so much for the replies. I asked this question because I had in my hands a 29 that comes from a range in my city that for 20 years only fired magnum loads and I saw that the upper strap had some marks like depressions and they told me it was due to the elongation. however the gun was so used that it was scrapped. I had another similar experience with a Ruger GP100 belonging to a friend of mine who, after having fired 20,000 rounds fully loaded, had the apper strap extended and some depressions could also be seen there. So I checked my 629 and saw a very small mark there too. In the photos you can see it with difficulty. Could this be a sign of some charges over the limit?
Feedback

 

[SnidelyWhiplash]

You would need S&W's specs on minimum and maximum tolerances on frame dimensions then have your frame measured to see whether it's beyond spec. I don't know whether S&W provides such info for the asking.

 

[stansdds]

Could have been fired extensively using heavy loads. What is the amount of end shake. Measure end shake with shim/feeler gauges. Push the cylinder full forward, measure the gap between the barrel and cylinder, then push the cylinder full backward and remeasure the barrel-cylinder gap. The difference is end shake. 0.001"-0.002" is ideal. More than 0.004" is excessive and a possible sign of heavy use or abuse. Look at the barrel's forcing cone. If you see significant erosion of the edge of the forcing cone, that is a sure sign of significant use of full power loads.

 

[Richard93]

Thanks so much for all the information, I'm glad I joined the forum. I will try to verify the measurements as you told me and I will write.
thank you so much

 

[Jmp50]

Is it on both sides?

 

[Richard93]

On the left side it is more evident and you can even feel it with your finger, on the right you can practically see nothing and feel nothing.

 

[steelslaver]

I do not believe you could stretch a frame unless the loads were well over maximum. Most end shake is the result of wear on the ratchet button and the mating surfaces at the end of the yoke tube and the cylinder where it rides on the tube.

An accurate measurement from the top of the recoil shield to frame above the barrel would tell the truth. You would need solid numbers from other N frames of the same vintage to compare though. But, I don't doubt that there are variations in the size of the frame window from one N frame to another simply due to manufacturing variations. Wear on cutters, variations from one milling machine and or hold downs to the next etc,

If I were going to be home longer I would measure all my N frames to get a clue.

I would also believe that if a frame stretched it would become out of square, as the top strap would be what stretched the most. This would also tilt the barrel down slightly.

I have never heard of a gun where the top strap failed before the cylinder, which is what would happen if the top strap was repeatedly streched beyond its elastic limit. Yes, there have been a few where the barrel separated at the frame, but I believe that was due to metal flaws

 

[Protocall_Design]

It seems that one of the things you are talking about is flame cutting on the top strap at the cylinder gap. That is normal, and you're not going to cut the top strap off. It will get to a certain point and stop getting bigger.

In the first picture you show soot or carbon at the barrel/frame junction. Is that just some that was on the outside that you didn't clean off, or is it coming up from a gap between the frame and barrel? If it's coming up from a gap, your barrel is about to break off.

 

[steelslaver]

In the first picture you show soot or carbon at the barrel/frame junction. Is that just some that was on the outside that you didn't clean off, or is it coming up from a gap between the frame and barrel? If it's coming up from a gap, your barrel is about to break off.

Put some masking tap over the barrel to frame juncture and firing a cylinder full should tell you if your barrel is cracked at the shoulder. That damage would not be from frame stretch. Possibly an over torqued barrel or some sort of other mechanical damage. N frames are pretty healthy there as they have a .670-36 barrel shank. .670-.429=.241/2=.1205 wall. On a K frame 357, .540-.357=.183/2=.0915. So a N frame 44 barrel is much more robust than a K frame 357
There is no crack under the barrel in the yoke cutout is there? Not unheard of in J and K frames, but, I do not think I have heard of it on a N frame.

 

[Richard93]

Maybe the photo I posted isn't well done. In reality what you see on the barrel is only a shadow. In the photos below you can see better. There is flame cutting (photo attached) but my question does not concern this aspect. My question concerns what appears to be a frame deformation indicated by the red arrow. Maybe I'm wrong but I ask you for your opinion.
I also measured the gap: 0.003" and the cylinder has no forward or backward play.

 

[Protocall_Design]

I don't see anything in the pictures that seems to be a problem. Frame stretching is extremely rare. If it was happening, the cylinder gap would be getting wider.

I can't tell what the arrow is pointing to. If it's an area where the top strap is thinner side to side, that was a manufacturing anomaly.

 

[Richard93]

Yes the top strap is thinner side to side.
Thank you very much for the information, since the gap has not increased it is certainly as you say. I haven't been shooting for many years and I still have many things to learn

 

[stansdds]

Maybe the photo I posted isn't well done. In reality what you see on the barrel is only a shadow. In the photos below you can see better. There is flame cutting (photo attached) but my question does not concern this aspect. My question concerns what appears to be a frame deformation indicated by the red arrow. Maybe I'm wrong but I ask you for your opinion.
I also measured the gap: 0.003" and the cylinder has no forward or backward play.

Based on the new photo and the end shake info, I think it's fine, just less than stellar machining, which is not uncommon with S&W.

 

[jaymoore]

Not so much machining, but polishing. I've seen this irregular transition on both blued and stainless revolvers. If the original polishing marks are still visible, you'll notice that they change direction in that area. The area photographed above is rather extreme, but probably only took a few seconds to generate on the polishing wheel. 99% sure that's all it is. Happy to be proved wrong, but the OP would be less pleased....

 

[SGT ROCK 11B]

Revolvers thrown out of bad guys/gals cars tend to be really messed up. But even dropping a revolver on a floor can mess it up.

 

[jaymoore]

BTW, the top strap's thinnest cross section is under the rear sight. If one were to stretch longitudinally it would most likely show at the recoil shield area. The only instance I can recall failure in such a way was in a roughly 50 cal. Tranter percussion revolver I had some 30 years ago. It had a crack at the rear of its top strap about half way through, starting on the underside. (The British nomenclature was, confusingly, a 38-bore. (AKA: "gauge"))

ETA: The "bent" frames I've seen on scrapped S&W revolvers fail through the thin area of the yoke cutout and at the rear of the top strap as well. Only when a cylinder lets go does the front end of the top strap seem to get badly distorted or break all the way before the back end. But not always. (We've rendered down several PD "evidence gun" accumulations prior to sale or destruction of the frames over the years. Plus the usual gunsmith "horror story" piles of ruined firearms gathering dust in bins and barrels....)