Fluted vs. Unfluted Cylinders

[Old Fuff]

Didn't fluted cylinders originate with the Colt 'pocket' models? Reduced size revolvers for the style conscious and effete.

Many of Colt's revolver-style long guns had fluted cylinders, as did early 1860 Army revolvers. They also made a prototype Dragoon "lightweight" with a fluted cylinder.

Fluting resulted in some weight reduction, but the extra milling and polishing operations added to the cost. I suspect that the extra cost of adding flutes whould make unfluted cylinders attractive to today's makers, but buyers now expect the flutes on most revolvers.

 

[unspellable]

A Ruger is built like a tank. On the other hand, an N frame S&W WILL wear at the hand and rachet faster than a K frame due to the bigger cylinder. So the difference in polar moment due to fluting or the lack of it may be significant in some cases.

 

[goodtime]

As far as the tradition of flutes goes, I'd define "traditional" not as "first on record," but something more like "a practice started a long time ago, which has been going on continuously since." The dictionary says: "a long-established way of thinking or acting. . ." and "customary or characteristic method or manner . . ." I think fluted cylinders fit both definitions, as they have been the predominant way of finishing cylinders for over a century.

 

[JamesKelly]

Matt Alemeda--yes, the flutes increase the strength of the chamber. Don't recall whether I learned this in a Mechanical Engineering or a Metallurgy class, but at the time I believe Ike still shot a decent round of golf.

My metallurgy professor, back in those civilized days, came in to class with an M1 rifle. Stripped it down, we had to decide what metal we would use for each part, how (or whether) we would heat treat it, and how would we make the piece in the first place. That is, forge, cast, stamp, machine from bar, cold draw, &c.

When the piece fires, the chamber is under uniform high gas pressure all the way around. When metal is stressed, it stretches, just like a spring. Removing some metal between chambers makes the expansion (stretch) more uniform, rather than concentrating that strain (stress, if you prefer) on the outside diameter of the cylinder, right over a chamber.

If it were practical to do so, the strongest revolver cylinder would be six smooth tubes, perhaps glued together. Kinda hard to rotate & lock such a device, so fluted cylinders are the best bet.

The earliest fluted cylinders I personally know about were Sam Colt's fluted cylinder 1860 Army. Dunno why he did it. Unfortunately,these cylinders were fluted too far back & burst simply from being too thin at the rear. He replaced these first, mostly burst, cylinders with more fluted cylinders, however the new ones had a tapered chamber so the rear portion near the nipple was thicker.

When any gun fires it is important that the barrel expand as uniformly as possible, to avoid concentrating stresses. Generally speaking, modern firearms are designed to do so.

A cool example of what happens when you restrain uniform expansion is to clamp a modern barrel (without the stock) in a good, strong machinists vice. Load, then pull the trigger. Using a long cord. The barrel cannot expand sideways, because the mass of that large vice restrains it. So all expansion is on the top and the bottom. The barrel will split.

I personally don't personally know if this will always split a centerfire rifle. But in Ancient Times (1940's, 1950's) it was widely known to.

I am not going to argue stress analysis with anyone. If you would like to know more about this, consult a mechanical engineer, preferably one with gray hair.

 

[unspellable]

There may be something in what JamesKelly states.

Street "wisdom" would have it that the weakest point is the bolt notch, or if it's offset, the center of the outer cylinder wall. How ever, such is not the case. Actual forensic metallurgical analysis shows that catastrophic cylinder failure usually occurs at the web between chambers.

This is the reason for super duper blasto magnums having five holes, thicker webs.

If the bolt notch was the weak point it would be a simple matter to offset the notch as is actually done in several makes of revolver.

Aside from forensic metallurgical analysis showing the failure point to be in the web I've seen the following torture test done on a S&W N frame chambered for 357 Magnum.

Chamber one: The outer side of the chamber was ground flat, level with the bottom of the notch for the entire length.

Chamber two: A slot was cut through the bolt notch for the entire length of the chamber, entirely through the wall.

Both chambers were fired with a standard 357 Magnum load with no failures.

Chamber three: No modification to the camber. How ever, a solid barrel was fitted with no bore what so ever.

Again, fired with no blow outs. (Note, the obstruction was at the barrel breech, not farther down the barrel, allowing the bullet and gas to build up more speed an momentum makes the effects more drastic.)

This is not to say that no cylinder ever failed at the outer wall, but the usual failure is at the web.

Cutting the flute just might allow the outer wall to expand a bit more sideways and relieve stress on the web.

As for the Super Blackhawk, that's so d**n strong the flutes aren't going to matter either way.

Stresses are not always where you think.