What-if 0081: "Catch"

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squall_line
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Re: What-if 0081: "Catch"

Postby squall_line » Wed Jan 29, 2014 8:34 pm UTC

ps.02 wrote:
Flumble wrote:Ah yes, I forgot to mention that explicitly: dropping the gun doesn't affect the velocity of the bullet radically. I'm not sure about the effects on the maximum height, though.

How much of muzzle velocity is attributable to bracing the gun and absorbing the recoil? My brain is too fuzzy this morning to do the math on that. Intuitively it seems like the bullet would come out noticeably slower if the gun is in free fall, as opposed to braced against the ground or your shoulder, but my intuition could be wrong. Perhaps the ratio of gun to bullet mass is already great enough for the difference to be negligible.


For a .22LR, such as the standard Remington 10-22, the recoil is fairly low. For a rifled slug shotgun, or a 50-caliber rifle, the recoil is fairly high. Leaving the gun unsecured by a shoulder or other back-plate will definitely affect the muzzle velocity, as per Newton's Third, but to a different degree on every gun, depending on the style of gun (semi-automatic or single-shot), gas mechanism (if any) and spring strength of the semi-automatic system, etc. A semi-automatic shotgun will have less recoil due to the gas mechanism absorbing and converting the energy into an ejection of the shell, but that doesn't mean that the muzzle velocity is reduced, the recoil is just used differently. I don't think that an un-braced semi-automatic shotgun would cycle or eject reliably, though.

See also: ballistic pendulums, etc.

Kintrex
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Re: What-if 0081: "Catch"

Postby Kintrex » Thu Jan 30, 2014 5:56 am UTC

So I have a question. What is being depicted in the fourth image? (I tried putting the picture in my post but it got flagged as spam.)

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Re: What-if 0081: "Catch"

Postby phlip » Thu Jan 30, 2014 6:18 am UTC

Kintrex wrote:So I have a question. What is being depicted in the fourth image? (I tried putting the picture in my post but it got flagged as spam.)

It's continuing the callback to Free Fall, which had pictures of both a guy in a wingsuit, and a guy using a phone while falling from the peak in question (though not at the same time).

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enum ಠ_ಠ {°□°╰=1, °Д°╰, ಠ益ಠ╰};
void ┻━┻︵​╰(ಠ_ಠ ⚠) {exit((int)⚠);}
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Re: What-if 0081: "Catch"

Postby sniper1rfa » Fri Jan 31, 2014 12:47 pm UTC

I'm actually curious about this bit, in one of the tooltips:

Of course, he was being figurative—you wouldn't see the bullet coming, so you'd be just as likely to catch it with your face as with your glove.



Which I suspect is possibly untrue.

I know from paintball that watching something inbound is much easier than watching it from the side. Paintballs go about 300fps, or 200mph. From the side they're difficult (though not impossible) to track. Coming straight at you, however, they are very easy to see and very easy to dodge, because all the velocity is in a direction that doesn't matter to your eyes. To the about-to-be-shot observer they're just slowly getting bigger.

You can even catch them, as long as they've slowed down enough that the impact doesn't break them (which isn't actually that slow, really).

Now, admittedly a bullet travels 3-10x faster depending on what it is, but I bet a barely supersonic, large bore handgun round would be visible in the right lighting, and at 1000 yards you might even have a chance of catching it reliably.

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Re: What-if 0081: "Catch"

Postby Mikeski » Fri Jan 31, 2014 8:55 pm UTC

sniper1rfa wrote:I'm actually curious about this bit, in one of the tooltips:

Of course, he was being figurative—you wouldn't see the bullet coming, so you'd be just as likely to catch it with your face as with your glove.

Which I suspect is possibly untrue.

I know from paintball that watching something inbound is much easier than watching it from the side. Paintballs go about 300fps, or 200mph. From the side they're difficult (though not impossible) to track. Coming straight at you, however, they are very easy to see and very easy to dodge, because all the velocity is in a direction that doesn't matter to your eyes. To the about-to-be-shot observer they're just slowly getting bigger.

You can even catch them, as long as they've slowed down enough that the impact doesn't break them (which isn't actually that slow, really).

Now, admittedly a bullet travels 3-10x faster depending on what it is, but I bet a barely supersonic, large bore handgun round would be visible in the right lighting, and at 1000 yards you might even have a chance of catching it reliably.

I suspect it's probably true. Your eye may take 10-12 "pictures" per second, but it also "post-processes" them to find useful information (your optic nerves are not even close to large enough to send the whole pattern on your retina to your brain). Your paintballs are large and brightly-colored and relatively slow and moving against a dark background. Bullets are tiny and dark and relatively fast and moving out of a bright muzzle flash (which will likely be the "important" info your eye sends to your brain). By the time your persistence-of-vision fades and your eye stops telling your brain "hey, check out this muzzle flash! think there's something dangerous over there?", you'd better have caught that bullet "blind".

Or, consider the guy firing the gun. He knows where the bullet is going (he's looking at it the whole time, hopefully), and I don't think he can see the bullet. When I've fired rifles, even at significant ranges, I've not been able to watch the bullet travel. I've never fired a large-caliber "slow" handgun, nor fired a rifle at something over a half-mile away, though. I'm not sure you could fire a .45 pistol at something 1000 yards away and expect the bullet to get there (50 yards is a reasonable max range for accuracy. 100 if you don't care what else around your target you might hit. 1000? Nope. You'd have to angle the shot up 30-45 degrees just to get it to go that far.)

That said, I'm not volunteering to test this. :wink:

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Re: What-if 0081: "Catch"

Postby Quizatzhaderac » Mon Feb 03, 2014 4:01 pm UTC

Gotta love the Coriolis riffling.

I think firing guns as they're intended to be used has little bearing on the situations at play here. Any situation where the bullet has lost 80-95% of it's speed is going to be ludicrously difficult to hit anything; well into the range of what marksmen and manufactures would label as an "impossible" shot. I'd say the paintball comparison might be fairly accurate.

The slug is denser than paint, so it will have less deceleration. If we're picking a distance where the projectile has slowed to a certain speed (say 40 mph) one would actually have more time to spot the slug than a paintball.

I'd also doubt the muzzle flash would be visible, let alone distracting at those distances. I have no citations for this, but I'd assume our vision is much better at processing "thing flying toward me" than "thing flying away".
The thing about recursion problems is that they tend to contain other recursion problems.

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Re: What-if 0081: "Catch"

Postby Zinho » Tue Feb 04, 2014 7:27 pm UTC

Mikeski wrote:Or, consider the guy firing the gun. He knows where the bullet is going (he's looking at it the whole time, hopefully), and I don't think he can see the bullet. When I've fired rifles, even at significant ranges, I've not been able to watch the bullet travel. I've never fired a large-caliber "slow" handgun, nor fired a rifle at something over a half-mile away, though. I'm not sure you could fire a .45 pistol at something 1000 yards away and expect the bullet to get there (50 yards is a reasonable max range for accuracy. 100 if you don't care what else around your target you might hit. 1000? Nope. You'd have to angle the shot up 30-45 degrees just to get it to go that far.)

That said, I'm not volunteering to test this. :wink:

I've got some experience watching bullets, so I'll chime in here. I had some Army training once where a 9mm tracer was used to simulate the firing of an anti-tank rocket; the bullets we fired were clearly visible in daylight as they flew downrange. I found it was slightly easier to follow them if I was an observer rather than the shooter; the cross-section visible from the side was larger and brighter. At the range we were engaging, the 9mm rounds seemed to be traveling at a sedate pace, and weren't difficult to follow at all. What I found striking about the experience was how much the rounds would drift away from a straight trajectory, and how far they'd travel after a ricochet off the ground or a lucky strike against one of the targets.

Spoiler:
TracerRounds.jpg

This image shows rifles used on a short range at night, but gives the idea. The long trails shown here are due to the high speed of the round relative to the long exposure time (it's night, after all). A slower (pistol) round in daylight would leave a shorter track on the film. The two ricochets match my experience; lots of energy left in the bullet after hitting a backstop intended to arrest it. Also, note the foreshortening of the track as the point of view gets closer to the round's trajectory - from the perspective of the shooter there's not much of a line there. Other details of note include the leftmost track, which starts a bit away from the barrel (exposure starts after firing) and the second-from-the-right which stops a few feet downrange from the firing line (fired just before the exposure ends). The rifles showing muzzle flash but no track are firing standard rounds, they probably only have 1 round in 5 as a tracer.
Long story short, I think the visibility issue for a bullet catch could be overcome; tracer rounds would definitely help. I also agree that I'd rather not be the volunteer with the catcher's mitt, unless my glove were lined with asbestos - tracer rounds are incendiary 8-)

EDIT: I noticed after finishing that I hadn't chimed in on the range/reduced round speed issue. I didn't say it explicitly above, but I suspect a good part of the reason for the simulator rounds drifting was the long range relative to the rounds' intended use. We were firing on targets well beyond any pistol's effective range, and the instructors knew it. As such the event was not being scored, it was only for familiarity. I suspect that trying to stand downrange of a rifle operating beyond its effective range would be as much of an exercise in frustration as trying to hit any of the targets on my rocket simulator range. The point of aim may very well be the safest place on the range to stand...

PS - for the curious, the rocket simulator consisted of a rocket launcher tube whose breech was replaced with a receptacle for a 9mm bullet, which fired when the rocket launcher's firing mechanism was activated. I wonder to this day how long the barrel was that the bullet was fired from - I wanted to stay on the range, so I resisted the temptation to look down the rocket tube.

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Re: What-if 0081: "Catch"

Postby Mikeski » Wed Feb 05, 2014 12:20 am UTC

...changing "bullet" to "tracer round" flips my argument on its head, of course. Now you're tracking something that's "trying" to be seen. Emitting more light than the muzzle flash, being as obvious as possible, working in a way that human persistence-of-vision and other eye/brain interface tricks make it more visible rather than less... It's like the difference between trying to spot a fireworks shell pre- and post-burst. Easier to see afterwards by a factor of hundreds, even though it's now much smaller and moving faster. Just because it's really really bright.

I think you'd agree that you couldn't really have seen the bullets at either end if they were ordinary bits of steel/lead, yes? (Except in the nigh-impossible case where the "target" was right at the bullet's maximum range/minimum speed, but somehow the shooter was still able to put it near a catcher's-mitt size target.)

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Re: What-if 0081: "Catch"

Postby cryptoengineer » Wed Feb 05, 2014 3:11 am UTC

Mikeski wrote:...changing "bullet" to "tracer round" flips my argument on its head, of course. Now you're tracking something that's "trying" to be seen. Emitting more light than the muzzle flash, being as obvious as possible, working in a way that human persistence-of-vision and other eye/brain interface tricks make it more visible rather than less... It's like the difference between trying to spot a fireworks shell pre- and post-burst. Easier to see afterwards by a factor of hundreds, even though it's now much smaller and moving faster. Just because it's really really bright.

I think you'd agree that you couldn't really have seen the bullets at either end if they were ordinary bits of steel/lead, yes? (Except in the nigh-impossible case where the "target" was right at the bullet's maximum range/minimum speed, but somehow the shooter was still able to put it near a catcher's-mitt size target.)


I've stood behind shooters firing Rem .223 from AR-15s. (~~M16 rounds). If the conditions where right, I could see the Mach shock waves coming off the round as it
went 200 yards downrange. But there was no chance in hell of seeing the round itself - it would have been a circle half the size of a dime. I've heard claims that
it's sometimes possible to see a non-tracer .45 if it gets silhouetted against the sky, on a long range shot. I *have* seen clouds of shotgun pellets when shooting
trap.

On the same 200 yard range, there was a 40 foot high sandy bank as a backstop. At the base, there was a large steel disk which rang iike a gong when hit. I found that I could hit it with my 10/22 using .22 LR, by 'walking' the aim point in, watching the spurts of sand where shots were hitting though the rifle's scope. By the time I was hitting the gong, I was 'aiming' at a point that was about 25 feet above it, with my sights set for 50 yards. So yes, they slow down a lot.

As for the 'falling gun' question - it's quite simple. Newton's 3rd law takes effect, and the relative masses of the bullet and the gun determine their relative speeds after the shot. Since the gun outweighs the bullet many to one, the bullet has an almost normal muzzle velocity, while the gun is only slightly accelerated. Of course, that's in the physicist's ideal world of frictionless planes and spherical cows. In reality, the guns center of mass is not on the axis of the barrel, so the shot will set the gun spinning, before it even leaves the muzzle.

ce

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Re: What-if 0081: "Catch"

Postby speising » Wed Feb 05, 2014 9:36 am UTC

cryptoengineer wrote: In reality, the guns center of mass is not on the axis of the barrel, so the shot will set the gun spinning, before it even leaves the muzzle.

that seems a strange design decision to me. wouldn't a centered barrel increase precision?

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Re: What-if 0081: "Catch"

Postby hamjudo » Wed Feb 05, 2014 1:06 pm UTC

I figured it out. Learn how to pack your own cartridges. Use a special powder load when packing your own bullets. A powder load so small that the bullet only travels 6 feet, when traveling straight up. Practice with that load until you know the issues and risks. Lower the gun, or raise the catcher, and increase the powder load to match. Keep scaling it up slowly and carefully and work out issues as they arise. Aiming will need to get progressively more accurate and repeatable. I imagine the gun will need to be mounted in some sort of precision fixture.

It will be expensive, and very time consuming, but not all science and technology is glamorous. Perhaps someday, Amazon packages will be delivered precisely with carefully controlled powder loads.

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Re: What-if 0081: "Catch"

Postby cryptoengineer » Wed Feb 05, 2014 5:06 pm UTC

speising wrote:
cryptoengineer wrote: In reality, the guns center of mass is not on the axis of the barrel, so the shot will set the gun spinning, before it even leaves the muzzle.

that seems a strange design decision to me. wouldn't a centered barrel increase precision?


Yes, it would. However, gun mechanisms and human anatomy make such a design impractical for handguns, and difficult for rifles.
"Barrel flip" has two sources - the aforementioned positions of the COM and the barrel, and the fact the the recoil force is applied
above the hand, which creates a turning moment.

You need to be able to sight the gun - shooting without using the sights works only in movies, or at point-blank range. This means you have to look along the barrel, or a line parallel with it. In a handgun which is supposed to be easy to carry, this means that the sights are close to the barrel, which must be in a location you can look along, and not blocked by your hand. For semi automatics and some revolvers, there's also the issue that the top part of the gun slides back an inch or so with each shot VERY FAST, to load the next round - you don't want your hand in the way.

There have been attempts to deal with this, such as the Mateba Autorevolver, where the barrel is on the bottom of the cylinder, and the sight on a raised rib: https://en.wikipedia.org/wiki/Mateba_Autorevolver. Another way it to 'port' the barrel, adding holes on top near the muzzle to direct some gases upwards, pushing the barrel down.

Even if the center of mass was on the line of the barrel, the turning moment cause by the hand not being in the same axis would still apply.

Full auto submachineguns have this problem in spades. Learning to control the barrel flip is critical, otherwise each shot will raise the barrel higher and higher. Beyond missing the intended target, this is very dangerous to the operator and anyone nearby. There's a reason Tommyguns (and many other subs) have a front grip.

ce

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Re: What-if 0081: "Catch"

Postby rmsgrey » Wed Feb 05, 2014 5:13 pm UTC

speising wrote:
cryptoengineer wrote: In reality, the guns center of mass is not on the axis of the barrel, so the shot will set the gun spinning, before it even leaves the muzzle.

that seems a strange design decision to me. wouldn't a centered barrel increase precision?


Precision isn't the sole, or even a primary, concern with handgun design - the main concerns are providing a suitable handle, a suitable trigger, a suitable firing mechanism, and a barrel that points in the right general direction. If you've ever tried playing quick-draw with a laser pointer, you'll realise that the main limit on precision for an amateur isn't the gun, but the person pointing it. Training with a gun will allow you to correct for recoil anyway, so eliminating it is a secondary issue. Most of the time, when a handgun's being fired, it's coupled to a fairly good recoil-damping system anyway (also known as a hand and arm) so low-recoil guns aren't going to need further recoil-elimination - and high-recoil is going to cause rotation at the wrist, elbow and/or shoulder unless the whole arm is locked with the barrel along the line through the shoulder.

It's only when the gun is free to move independently that the barrel being off-centre is significant.

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Re: What-if 0081: "Catch"

Postby Zinho » Wed Feb 05, 2014 6:45 pm UTC

Mikeski wrote:I think you'd agree that you couldn't really have seen the bullets at either end if they were ordinary bits of steel/lead, yes?
Agreed, I probably could not. To be honest, I have trouble tracking golf balls, although that may have something to do with my swing... Others with more rifle-shooting experience may be able to do better than me.

speising wrote:
cryptoengineer wrote: In reality, the guns center of mass is not on the axis of the barrel, so the shot will set the gun spinning, before it even leaves the muzzle.
that seems a strange design decision to me. wouldn't a centered barrel increase precision?
Already expertly answered, but I thought I'd add another tidbit - the rifling on the barrel causes both spin on the bullet and a reaction twist around the barrel's long axis. You're pretty much not going to prevent the rifle from rotating if it's in the air & unsupported when fired. That said, I'd totally watch a Mythbusters episode where they tried to do precision shooting using a rifle in freefall. Watching Adam shoot himself would be hilarious in a tragedy+time sort of way :twisted:

hamjudo wrote:I figured it out. Learn how to pack your own cartridges. Use a special powder load when packing your own bullets. A powder load so small that the bullet only travels 6 feet, when traveling straight up. Practice with that load until you know the issues and risks. Lower the gun, or raise the catcher, and increase the powder load to match. Keep scaling it up slowly and carefully and work out issues as they arise. Aiming will need to get progressively more accurate and repeatable. I imagine the gun will need to be mounted in some sort of precision fixture.

It will be expensive, and very time consuming, but not all science and technology is glamorous. Perhaps someday, Amazon packages will be delivered precisely with carefully controlled powder loads.
Ultimate goal? Artillery-powered spaceflight. Mental note: monitor hamjudo for signs of SRMD (WARNING: TVTropes link) and secure funding for his research. THIS NEEDS TO HAPPEN.

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Re: What-if 0081: "Catch"

Postby Tomlidich the second » Mon Feb 10, 2014 6:13 pm UTC

this could actually work, with some alterations:

slower speed round, like .45 acp or .38 special (about 800 FPS and lower)

also, tracer ammo to make it easier to see mid flight. (though this creates some logistic problems should you hit something unexpected)

gonna need some kind of heat resistant kevlar gloves as well.

if you wanna get really creative, your best bet would be slowing the bullet down, not just with gravity, but with air resistance.

bullets are conventionally made of lead, because its heavy. we would make them from gold if it was cheap enough.

some manufacturers make them form other materials.


if you choose a wide, somewhat obtuse aerodynamic shape, make it out of a lighter alloy, and fire up, air resistance will do a world of good in slowing it down.

so, say, a blackpowder revolver loaded with aluminum ball ammo.
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