Big gun question

[jeffcoslacker]

Just curious...thought someone might know. i was cleaning a gun today and the rifling got me to thinking...I suppose that as the bullet engages the rifling, there must be some (perhaps negligible) amount of torque transferred to the barrel and weapon as it does...three questions came to mind:

1. Does this figure into the threading of the barrel at all? Seems that it could hammer away at the barrel and loosen it up over time, if not threaded so that it would provide torque in the correct direction to make it stay tight? I know barrels can have twist in either direction, depending on the gun.

2. In really big rifled guns, like say the 16 inchers on the USS IOWA, I start to wonder if that force could be considerable? Or not? I don't know how those barrels are mated to the guns, but just wondered if that force has to be considered and if designs address it in some way, or again, just not a big enough force to worry about?

3. Why can't I look through a barrel without hearing the 007 theme in my head? [emoji2]

[VRH]

I have a friend who had a revolver in 500 Linebaugh. I never shot it, I just watched. What I saw was that he did have a little bit of revolver twist when he fired it. The only thing we could think was that when the bullet hit the rifling, it caused the revolver to twist a wee bit.

With respect to barrel erosion, that does happen over time. It happens faster with jacketed bullets than with lead and the Brinell hardness of the bullet plays a part when the bullet obturates into the barrle.

[Tbeck]

Nope no twist on the barrel. Bullets are made of soft metals to conform. Even with the soft bullet materials a small amount of rifling will wear off, but any twisting is absorbed by the bullet and rifling itself. If I was to own a weapon or two, I might own a few with interchangeable barrels, and some of them might screw in.
I could be wrong on the REAL big military grade stuff, but I think that most are smooth bore, I know the 105 is.

[jeffcoslacker]

Nope no twist on the barrel. Bullets are made of soft metals to conform. Even with the soft bullet materials a small amount of rifling will wear off, but any twisting is absorbed by the bullet and rifling itself. If I was to own a weapon or two, I might own a few with interchangeable barrels, and some of them might screw in.
I could be wrong on the REAL big military grade stuff, but I think that most are smooth bore, I know the 105 is.

Big battleship guns are rifled, the rounds have copper drive bands around them that interact with it...

[JFL Live]

It looks like the 16"/50 caliber Mark 7 gun is rifled. But more interesting to me...

These guns were 50 calibers long—or 50 times their 16-inch (406 mm) bore diameter, which makes the barrels 66.6 feet (20 m) long, from breechface to muzzle. Each gun weighed about 239,000 pounds (108,000 kg) without the breech, and 267,900 pounds (121,517 kg) with the breech.[1] They fired projectiles weighing from 1,900 to 2,700 pounds (850 to 1,200 kg) at a maximum speed of 2,690 feet per second (820 m/s) with a range of up to 24 miles (39 km). At maximum range the projectile spent almost 1½ minutes in flight.[1] Each turret required a crew of 79 men to operate.[1] The turrets themselves cost US$1.4 million each, to which the cost of the guns had to be added.

Wiki

[RoadKing]

I was in a 175 mm gun battalion in the early 60's. The tubes were rifled. Due to the charge there was a shelf life to the tube. Charge three (max) was good for only three rounds if memory serves me well, a range of 26 miles with nuclear tips. From what I was told a few days ago artillery pieces are making a comeback because rockets are too easily hacked.

[Tbeck]

Interesting! I learned something new tonight. Might have to look into this more when I have time.
Dr Bob would have been the go to guy on this

[Herb]

Traditionally the brits used a left hand twist and american use a right hand twist.

pretty good article on the issue.

http://dailycaller.com/2014/02/09/why-i ... ht-handed/

Yesterday I was reading about the kimber micro 9 and it said it had a left hand twist. I got curious about it and did a little research on the subject.

Kinda odd that this subject came up today...

[Forge]

Yesterday I was reading about the kimber micro 9 and it said it had a left hand twist. I got curious about it and did a little research on the subject.

Kinda odd that this subject came up today...

It's an omen. You need that gun now.

[Herb]

Yesterday I was reading about the kimber micro 9 and it said it had a left hand twist. I got curious about it and did a little research on the subject.

Kinda odd that this subject came up today...

It's an omen. You need that gun now.

Nope, not at their price.

My next firearm is gonna be the Ruger LCP.

[Forge]

Yesterday I was reading about the kimber micro 9 and it said it had a left hand twist. I got curious about it and did a little research on the subject.

Kinda odd that this subject came up today...

It's an omen. You need that gun now.

Nope, not at their price.

My next firearm is gonna be the Ruger LCP.

I have an older LCP and think it's a great tiny pocket carry piece for when I'm wearing shorts and it is also nice and light weight. Before my back surgery, belt and inside the waistband carry were possible so I carried a M&P 40 compact. On cooler days, I would carry my M&P 45 with a flannel shirt loosely worn over. Since the surgery, I cannot wear a belt and switched to wearing suspenders so belt and iwb carry are out and I switched to pocket carry. Now my 2 go to guns are my LCP 380 and my M&P Shield 45 when I wear relaxed fit jeans.

[RoadKing]

Been a rifleman ever since the military. They definitely have rifling and torque has never been an issue. Bit of a kick on my Marlin is all.

[jonnycando]

There's many an old shooting iron about, and it's been my experience...if it shot straight new, it'll shoot straight for thousands of rounds. That said, anything can wear out...and if you find a favorite old gun isn't right, and can't figure out why....well...maybe the rifling is flattened and the bullets are coming out waywardly.

Three shots and it's retired? Even if they are nuclear tipped rounds, I find that a worthless barrel.

[jeffcoslacker]

I'm not sure anyone has yet totally grasped the nature of what I was wondering about...rotational forces (torque), especially sudden, can do big things over time or with repetition. That's the nature of an impact wrench. And even though it may be a very small force, if you're firing projectiles so heavy and so far that you have to factor in Earth's rotation and Coriolis Effect, etc, seems any other small forces acting upon the gun itself would matter. Exceptionally small variances at the beginning of travel turn out as huge errors towards the termination of any ballistic flight...

Ever see racing brakes/wheel mountings that use directional fastener hardware specific to the side of the vehicle its used on? That addresses this issue. Your street car, not an issue. Race car? Can be. I'd think that in the case of a threaded barrel anyway, each time a bullet suddenly engages the rifling, it's forced to spin (duh), so that energy that causes that to happen HAS to have an equal and opposite effect on the body causing it (that's the third law, ask Newton), so there IS at least SOME (equal) amount of torque being applied to the barrel. TANSTAAFL in physics.

In the case of a threaded barrel, this would almost have to act as a force to either tighten or loosen it, depending on the direction of the threading. It may be inconsequential, but it IS there. That is what I was asking.

[Tbeck]

Jeffco, I know what you wanted to ask, but I think it is so insignificant as to not have much of an impact. My weapons (if I was to have any) with spun lock barrels, have never loosened, regardless of how hot the ammo pushed through. Obviously barrel build is proportionate to the intended load and projectile being used. But I think that the rifling in any barrel would provide the absorption necessary to negate the initial rotational force.
I am sure you could likely get an answer or explanation from someone at Ruger, Remington, etc... smaller design but same principle's

[Yooper]

I'm sure that there is more than a few on here that have several barrels for the same gun? On the ones I have that I can swap barrels, I just tighten and remove them by hand. Never had one loosen or tighten from shooting. If that was the case, what's that going to do to your head space? Good post Larry, it bears thinking about.

[jeffcoslacker]

I'm sure that there is more than a few on here that have several barrels for the same gun? On the ones I have that I can swap barrels, I just tighten and remove them by hand. Never had one loosen or tighten from shooting. If that was the case, what's that going to do to your head space? Good post Larry, it bears thinking about.

Yeah but my question there would be, is the direction of your rifling such that any torque action from this effect (however slight) would simply keep the barrel tight? I would have to know the direction of twist, and the direction the barrel tightens.

Put it this way. Say you put the barrel on loosely and fire it several times (please don't do it)...now all other considerations aside about what would happen, if the twist in the rifling is one way, I guarantee you that at some point it will have spun the barrel on the threads a bit each shot, and whether that would be tighter or looser would depend on the direction of the rifling vs the direction of the barrel threading.

That being the case, one would assume that just to cover all eventualities, they would be preferentially machined and matched in such a way that the default action would be to tighten the barrel, not loosen it.

If that is the case, that's all I wanted to know. [emoji2]

[jeffcoslacker]

Well I've just thrown myself another mental hurdle...

I've been thinking of the torque acting on the gun solely in terms of rotational force around the center axis of the barrel...but I just realized it would actually be tangential...anyone wanna take a stab at why? [emoji2]

[Yooper]

Tangential force? Way over my head. But here is what I can do Saturday when me in the wife pop a few rounds out in the backyard. I can screw in a barrel by hand, make a mark on both ends where they meet and fire a few rounds to see if the marks change. Not scientific, but would maybe show a change? I just have this funny feeling there are more forces around than centrifugal, and that's the only force I've ever thought of. I read somewhere that my Mosins 7.62X54R were spinning at close to 300,000 RPM Sounds like ridiculous high, but don't know.

Edit to say if the marks do move, isn't that gonna change head spacing? Larry, I hate it when you get me thinking on a nice sunny 65 deg day.

[jeffcoslacker]

OK...just talked for a while with my stepfather...even though he knows ZIP about guns and is diametrically opposed to them, he was a great person to ask, because he is a retired physics professor and mathematician.

Upshot: Yes, there is torque there. No, it is pretty weak, as it only needs to rotate the bullet along its long axis, which is pretty easy to do. Still it transmits this suddenly to the barrel upon engaging the rifling and ultimately the gun, but in the case of a handgun, would be largely negated by the overall force of recoil, as well as being dampened by the off-center and considerable mass of the gun's frame and mechanicals in your hand. In plain words, you're not going to feel it. Just as the Earth moves SLIGHTLY in the opposite direction when you jump up, the amount is only in proportion to the differences in the masses involved. That small amount of lead and copper, and the energy required to spin it around its axis, is very insignificant to the overall mass of the gun and even the hand/arm grasping it.

BUT, at the barrel/frame interface, he figured that as I said earlier, if it was loose and you fired it, any amount of torque imparted to the barrel would serve to rotate it on the threads, even if just a small amount, and he agreed that just in the interests of covering every eventuality it would make sense to have rifling and barrel threading that compliment each other in that respect...but he suspected that in actual practice, it probably makes no difference. Plus what I just said about tangential force does apply...as well as trying to spin the barrel in the opposite direction of the round's spin, the round is also pulling the barrel forward, by friction with the rifling lands, as well as the thrust of the powder charge being mostly contained behind it until it exits the barrel...so the torque reaction trying to rotate the barrel would have to contend with the force on the the threads of the barrel as it's being pulled forward strongly...and it most likely wouldn't be able to overcome it. Think like taking a nut off a bolt that is under no load, versus one that has 2000 pounds hanging from it (watch your feet!). Bit of difference in effort to rotate it.

Now when we shift to huge calibers with floating barrels and such, it gets a little more difficult to say...we agreed we'd both have to have a better understanding of the way they are built and the speed of twist involved, etc, to say anything with certainty...