Posted: 4/6/2017 7:00:52 AM EDT
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Can someone tell me how to convert a.....
Just kidding! 
I had a thought while I was taking Obama to the pool. I have so few of them I couldn't let it go to waste. How far does the first round travel before the second round fires? This doesn't apply to arf-snipers I am sure, but at distances for mere mortals does the first round impact the target before the second round leaves the barrel? Obviously it varies almost infinitely, but surely we can take some common guns and math the rpm and the fps. Is it that simple? Dun befo? |
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Depends on the cycle rate of the auto gun.
A Glock 18 shooting +P 124 grain, with a cycle rate of 20 rounds per second, has each round clearing the crown of the barrel at 0.05sec. Assuming 1150fps, about 57ft downrange before the other round get to the end of the barrel. edit, hard to answer the question without a high frame rate camera, as the bullet has to go from rest, and accelerate up to its max velocity, and that is not linear. |
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Lets take all the best numbers and see if everything works out perfectly, how close together the first two rounds are:
M16 Cyclic rate, 950 rds/min (maximum) M855 muzzle velocity M16: 3150 ft/s 60 (seconds/min) / 950 (rds/min) = .06 (seconds/round) So 0.06 seconds after the first round is fired, the second round is fired. Assuming the bullet achieves instantaneous velocity of 3150ft/s upon firing 3150 (ft/s) * 0.06 (seconds/rd) = 198.9 ft/rd So lets round to 200ft or so. At 700 rds/min (m16's lowest listed cyclic rate), you are still at 270ft or so. In actuality you will be closer than that as well, as bullet 1 is affected by drag in air before bullet two leaves, so you can't assume a constant velocity of 3150 through the entire .06 seconds, but it gives us a good idea at least. Since 100 yds is 300 ft, it is pretty safe to assume if your target is 100yds or more out, your 2nd bullet will fire before your first bullet impacts the target. #theydidthemath |
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Using smaller numbers, let's say 800 rpm MP5, shooting 1200 fps 9mm.
That's firing every .075 seconds. Velocity, since the bullet doesn't leave the chamber at 1200, will be an average of 0 and 1200, so 600 fps. 600 fps x .075 sec = 45 feet So 115 grains of lead every 45 feet. This distance can also be visually seen if you shoot in the dark with a weaponlight. You can see the bullets in flight. |
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Quoted:
Using smaller numbers, let's say 800 rpm MP5, shooting 1200 fps 9mm. That's firing every .075 seconds. Velocity, since the bullet doesn't leave the chamber at 1200, will be an average of 0 and 1200, so 600 fps. 600 fps x .075 sec = 45 feet So 115 grains of lead every 45 feet. This distance can also be visually seen if you shoot in the dark with a weaponlight. You can see the bullets in flight. Acceleration from 0 over a known distance with a known final velocity is a= v2 / 2s where s is the barrel length and a is acceleration. Mp5 barrel length is 8.9in = ~0.75 ft so acceleration is 960000 ft/s2 That means you reach 1200 ft/s in only .00125s, which is only 1.6% if your total flight time between firings. |
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Depends on the gun. With an M-3 the first round is about a 1/2 mile down the road before the second round fires.
Bang........Bang...........Bang...........Bang. ETA: I loved those Grease guns. Who can't love a fully automatic machine gun with only 1 moving part. |
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Depends on the gun. With an M-3 the first round is about a 1/2 mile down the road before the second round fires. Bang........Bang...........Bang...........Bang. ETA: I loved those Grease guns. Who can't love a fully automatic machine gun with only 1 moving part. 
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one or two episodes back on FXs Legion there was some subgun fire indoors in a small room. guy froze time and there was a string of bullets about 1ft apart in the air. dudes do special effects better than they do math.
at least it wasnt loaded cartridges in the air, i have seen that in more than 1 movie. |
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This seems like a great thread to post my M11/9.
If there ever was a gun where the bullets would damn near bump into each other as they fired...this would be it.
[youtube]https://www.youtube.com/watch?v=5Xc5GcQLB0I[/youtube] clickable: https://www.youtube.com/watch?v=5Xc5GcQLB0I Damn I miss that thing. |
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Actually, this is not a safe assumption for average velocity. Yes, the bullet is not going 1200ft/s right away, but it certainly not average of 600 for the entire 0.075s. Acceleration from 0 over a known distance with a known final velocity is a= v2 / 2s where s is the barrel length and a is acceleration. Mp5 barrel length is 8.9in = ~0.75 ft so acceleration is 960000 ft/s2 That means you reach 1200 ft/s in only .00125s, which is only 1.6% if your total flight time between firings.
I will defer to your reasoning, since you're more mathematically inclined than I. |
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http://www.everydaynodaysoff.com/wp-content/uploads/2014/11/Blocked-Squib-Barrel-357-Magnum.jpg Occasionally, not very far. |
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The bullets fly much faster than the cycle of the action. First bullet impacts target well before the second round is fired. At least under most normal circumstances.
I suppose you might be able to get the second round off before the first round hits the target if you were shooting a slow moving round like a 45acp at a far enough distance like 1,000 yards with a fast shooting gun like a MAC-10. But good luck hitting the target, haha, not practical at all. The idea of the HK G11 rifle was that it fires a 3 round burst so fast that you would only feel one recoil impulse, which was a pretty cool idea. They were able to achieve this using case-less ammo. |
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Quoted:
Can someone tell me how to convert a..... Just kidding!
I had a thought while I was taking Obama to the pool. I have so few of them I couldn't let it go to waste. How far does the first round travel before the second round fires? This doesn't apply to arf-snipers I am sure, but at distances for mere mortals does the first round impact the target before the second round leaves the barrel? Obviously it varies almost infinitely, but surely we can take some common guns and math the rpm and the fps. Is it that simple? Dun befo? 
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Quoted:
What's the story here? Quoted:
Quoted:
http://www.everydaynodaysoff.com/wp-content/uploads/2014/11/Blocked-Squib-Barrel-357-Magnum.jpg Occasionally, not very far. |
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Bulletstorm, and Minigun make this much more interesting.
Technically it depends upon the range the gun is fired at: in a room target is hit before next round is fired, at 1 km that isn't so much the case All depends on the gun, bullet speed, range etc. Think of how gas operated mgs work, they reload after bullet passes a certain point, so from that point add the time to cycle the next round and fire. I don't have a damn clue about the specifics. Someone else could probably expand upon this. |
| Back in the early days of the M-16A2, (I was in the 7th series in boot at MCRD to get the rifle, brand new from the box) we were told that on burst, with the new 62gr round, we could hit targets at 800 meters on burst. Never fired further than 500, and never on burst. |
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Back in the early days of the M-16A2, (I was in the 7th series in boot at MCRD to get the rifle, brand new from the box) we were told that on burst, with the new 62gr round, we could hit targets at 800 meters on burst. Never fired further than 500, and never on burst. |
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FPS of the bullet divided by cycle time would get you about three hundred feet that the first bullet would travel before the second bullet fired for a 3000fps bullet with 600 rpm cycle time. If my math is wrong fix it! |
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FPS of the bullet divided by cycle time would get you about three hundred feet that the first bullet would travel before the second bullet fired for a 3000fps bullet with 600 rpm cycle time. If my math is wrong fix it! So 3000*60/600 = 300 feet Or using approximate figures for an M4 with a 14.5" barrel and M855: 2900*60/850 = 205 feet |
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Quoted:
What's the story here? Quoted:
Quoted:
http://www.everydaynodaysoff.com/wp-content/uploads/2014/11/Blocked-Squib-Barrel-357-Magnum.jpg Occasionally, not very far. 
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Is he Italian too?
