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 June 3, 2017, 09:57 AM #1 TXAZ Senior Member   Join Date: September 5, 2010 Location: McMurdo Sound Texas Posts: 4,322 Fastest possible bullet in theory? What is the maximum possible speed of a bullet, given an ideal (trying to keep it easy): A very small projectile (near zero mass) A large amount of propellant (whatever that may be) A perfect seal between the bullet and the barrel Zero resistance between the bullet and the barrel There is no barrel twist All energy in the gunpowder is converted into forward kinetic energy Is the maximum theoretical speed of the bullet the same as the speed of the burning wave front? Thanks in advance. __________________ Cave illos in guns et backhoes
June 3, 2017, 10:47 AM   #2
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 Is the maximum theoretical speed of the bullet the same as the speed of the burning wave front?
If you can remove all friction, so that all the energy goes into propelling the bullet, then in theory, you would get CLOSE to the speed of the powder gas.

Close, because even if you could remove all friction, you can't remove the inertia of the mass of the bullet. It will take some energy to accelerate the bullet from rest.
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All else being equal (and it almost never is) bigger bullets tend to work better.

 June 3, 2017, 06:28 PM #3 JohnKSa Staff   Join Date: February 12, 2001 Location: DFW Area Posts: 24,694 I believe the M1 Abrams main gun uses fairly standard propellant. It achieves a muzzle velocity between 5000 and 6000fps. That is done with a smoothbore barrel and a sabot round so it's not exactly comparable to a rifled barrel firearm. __________________ Do you know about the TEXAS State Rifle Association?
 June 4, 2017, 08:58 AM #4 mapsjanhere Senior Member   Join Date: August 6, 2009 Location: Albuquerque Posts: 2,832 The German WWI Paris gun still holds the record for a conventional "practical" gun (practical in a limited sense, they achieved the speed by using a set of steadily growing rifling rings to make up for excessive barrel abrasion). You can achieve much higher velocities with a light gas gun. In it a conventional charge compresses a hydrogen or helium gas to very high pressures, and it's fired by a burst disc releasing the pressure. You can get up to 25,000 ft/s that way. __________________ I used to love being able to hit hard at 1000 yards. As I get older I find hitting a mini ram at 200 yards with the 22 oddly more satisfying.
 June 6, 2017, 12:48 AM #5 Scorch Senior Member   Join Date: February 13, 2006 Location: Washington state Posts: 15,241 I have read that the shock wave from smokeless propellant travels at just over 6.000 fps, so that would be your theoretical limit using conventional propellant. People have hit around 5,400 fps in 22 centerfire rifles. __________________ Never try to educate someone who resists knowledge at all costs. But what do I know? Summit Arms Services
 June 6, 2017, 11:25 AM #6 Gunplummer Senior Member   Join Date: March 11, 2010 Location: South East Pa. Posts: 3,364 The Germans were working on some type of large bore, long barreled cannon that had "Boosters" at various stages of the tube. I never had enough interest in cannons to read the rest of the article to see how it worked out.
 June 6, 2017, 12:38 PM #7 T. O'Heir Senior Member   Join Date: February 13, 2002 Location: Canada Posts: 12,454 Abrams main gun gets there with the DU penetrator of an APFSDS round only. The General Dynamics KEW-A1 has a muzzle velocity of 1,740 m/s (5,700 ft/s). The issue with rifle bullets is mostly the bullet. A lead cored bullet cannot get going too fast due to the heat created melting the core. A solid is a different story though. You still run into instability caused by heat. I seem to recall some guy playing and got around 5,000 plus fps. Forget where or who though. __________________ Spelling and grammar count!
 June 7, 2017, 10:09 AM #8 random guy Senior Member   Join Date: February 28, 2017 Posts: 272 I think you've gotten your answer for conventional "gunpowder". Railguns produce higher velocities using non-conventional propellants but it's really beyond anything that's on our horizon as individuals. Sabot rounds (including tanks' main guns) get very high velocities simply because the projo is light for caliber. But then they discard their sabot and fly like normal, or even long for caliber rounds outside the barrel. That is technology that we should be able to use in small arms right now. It's probably just a matter of time before someone makes this work well and puts a lot of conventional HV rounds in the shade.
 June 8, 2017, 09:49 AM #9 Jimro Senior Member   Join Date: October 18, 2006 Posts: 7,097 Fastest possible in theory is the speed of gunpowder expansion minus the energy required to overcome inertia minus loss to friction. The problem becomes that in reality, as bore size decreases friction increases (why you have to pump harder to get the same amount of water through a smaller pipe than a larger pipe), so you are left with trying to find the right compromise of bore diameter to chamber volume. Because chamber volume...as it increases you can put more powder in it, but in order to not destroy the firearm it must burn slower, so in order to harness more of the potential energy the barrel must be made longer.... So to get more velocity, engineers try tricks like discarding sabots to get the decreased friction and energy transfer of a large bore, but with a projectile mass of a smaller bore. Or they try to use a squeeze bore where the projectile starts out one diameter, and is then reduced in diameter to get an increase in velocity like going from a big hose to a small hose (same volume into a decreased diameter pipe equals more velocity). In practice, WWII era squeeze bore anti tank guns got into the 4,600 fps range, and as already stated the 120mm smoothbore cannon can get up to 5,700 fps. At this point tank gun designers (unless they are German then it is Panzer kanone designers) aren't trying for more velocity, but more mass. Rheinmetall is working on a 130mm gun and the US military flirted with a 140mm gun, the Russians seem to be sticking to the 125mm bore for now. And essentially everyone has abandoned the squeeze bore concept for the time being. Jimro __________________ Machine guns are awesome until you have to carry one.
June 8, 2017, 10:31 AM   #10
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 Sabot rounds ... That is technology that we should be able to use in small arms right now. It's probably just a matter of time before someone makes this work well and puts a lot of conventional HV rounds in the shade.
Remington Accelerators.

4000+fps from a .30-06!!

55gr .224 bullet in a plastic sabot, made in .30-30, .308 Win, and .30-06. No others that I know of. Haven't seen any in ages, I think Remington stopped making them a while back.

Turned the .30-30 into a .222, the .308 into a .22-250, and the 06 into something that beat out the .220 Swift for velocity.

The idea was to be able to turn your average deer rifle into a varmint rifle, simply by changing ammo. It didn't work well. Accuracy was the big problem. Most rifles grouped them ...poorly.

A few (apparently only a very few) would shoot them as well as they shot regular "deer" loads, and nobody's really happy with a minute of deer varmint rifle. And then there were complaints about plastic fouling, as well.

The 120mm cannon gets around the fouling issue by being smoothbore, and tank sighting systems are just a bit more refined and complex than what we usually mount on a rifle. And I would assume that minute of tank at 2000 meters is just slightly different from MOA at 100.

The key to sabots in modern small arms isn't getting something that works, its getting something that works WELL, (meaning high velocity AND accuracy) and so far, no one has.
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All else being equal (and it almost never is) bigger bullets tend to work better.

 June 8, 2017, 12:39 PM #11 mapsjanhere Senior Member   Join Date: August 6, 2009 Location: Albuquerque Posts: 2,832 Also, tank guns have a little "tooth" at the muzzle to initiate the controlled disintegration of the sabot. Rifle sabots need to disintegrate on its own, adding an additional degree of complexity. __________________ I used to love being able to hit hard at 1000 yards. As I get older I find hitting a mini ram at 200 yards with the 22 oddly more satisfying.
June 8, 2017, 04:57 PM   #12
random guy
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 Remington Accelerators. done decades ago!!!
Yep. Never tried them but some people said they shot as well as the rifle in question would shoot normal ammo. That is probably the best case scenario. And as you say, most deer rifles do not have varmint rifle accuracy.

But Remington only tapped half the potential, the other half being long, probably fin stabilized bullets. Long range shooting and long bullets are highly popular today and the ultimate development AFAIK would these miniature tank guns.

I don't know if such a system can be made to work for commercial use and at a non-government price. IIRC 120mm sabot rounds are well over \$1000 apiece and that includes steel training rounds.

If we are ever going to see it, it will probably be in military use first. There is the .50 BMG SLAP round but that is basically a bigger "Accelerator" needing a rifled barrel.

 June 8, 2017, 05:15 PM #13 Slamfire Senior Member   Join Date: May 27, 2007 Posts: 5,261 I believe in the 1920's there were experiments with swage bore weapons that pushed projectiles up to 6000 fps. These barrels got smaller by a considerable amount as the projectile approached the muzzle. I recall that bore life was horrible. __________________ If I'm not shooting, I'm reloading.
 June 9, 2017, 06:20 PM #14 mapsjanhere Senior Member   Join Date: August 6, 2009 Location: Albuquerque Posts: 2,832 The Germans made some pretty effective light and medium anti-tank guns based on that concept during WWII, especially a 28 -> 20 mm. Luckily for the US they didn't have enough tungsten for the rounds, and didn't know about using uranium (depleted uranium rounds haven't been invented yet). __________________ I used to love being able to hit hard at 1000 yards. As I get older I find hitting a mini ram at 200 yards with the 22 oddly more satisfying.
June 9, 2017, 06:31 PM   #15
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 didn't know about using uranium (depleted uranium rounds haven't been invented yet).
WE didn't know about using depleted Uranium as a projectile, until several decades after we first created depleted Uranium in 1945.
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All else being equal (and it almost never is) bigger bullets tend to work better.

 June 11, 2017, 05:04 AM #16 Hal Senior Member   Join Date: October 9, 1998 Location: Ohio USA Posts: 8,563
 June 13, 2017, 12:49 AM #17 James K Member In Memoriam   Join Date: March 17, 1999 Posts: 24,383 Probably the best known "squeeze bore" sporting rifles were those made in Germany in the 1930's by Halbe & Gerlich (who combined their names into "Halger" which they used as a trade name for a high velocity rifle. The idea was to make the inside diameter of the barrel tapered so that the pressure increased as the bullet was reduced in diameter. IIRC, the bullet was not really "squeezed" down, because that would distort it, but a sort of "skirt" was used to allow the bullet to pass through the barrel as the hole became smaller. The idea worked, but the cost of making the special barrels was too high to be practical in a sporting rifle. It was later used in tank and anti-tank guns, though, and gave reasonably good performance, but was superseded by shaped charge projectiles which did not require high velocity to penetrate armor. Jim
July 12, 2017, 03:58 PM   #18
hdwhit
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Quote:
 TXAZ wrote: What is the maximum possible speed of a bullet...
The maximum possible speed of a bullet in ballistic flight in air is the speed at which heating caused by air resistance and other aerodynamic forces destroy the projectile. So, the answer is, "It depends on the projectile".

 May 19, 2020, 06:02 PM #19 Atticus Thraxx Senior Member   Join Date: October 23, 2007 Location: Yolo County CA Posts: 314 If you're not stuck on propellants and closed bores, the rail gun opens up interesting possibilities. > 3km/s last I read. I'd post a link but I'm not yet sure what's ok. __________________ "No Curling in the Squat Rack!" Looking for K98 bolt #5954 and K98 bolt #31942 for trade. DM me if you have a match. Prizes will be awarded!
 May 20, 2020, 02:20 AM #20 44 AMP Staff   Join Date: March 11, 2006 Location: Upper US Posts: 27,736 Really? We're bringing this one back after almost 3 years? not the record but still not a great idea....oh well... Between 5 and 6 thousand fps has been achieved with gunpowder. That's about the limit for gunpowder. If you want to go faster, its rail gun tech time. There you can get the highest speed possible on earth. Escape velocity. And a bit beyond I think. We haven't done it, yet, that I know of, or at least not outside a lab. __________________ All else being equal (and it almost never is) bigger bullets tend to work better.
 August 6, 2020, 12:03 AM #21 Dizzipator Senior Member   Join Date: November 14, 1999 Location: - Posts: 156 Flywheel Stress There’s one other consideration that I didn’t see mentioned, in so far as limitations on the rotation speed of the projectile. Spin the bullet too fast and it will be torn apart when the hoop stress exceeds the tensile strength of the bullet. An old time MIT trained mechanical engineer (Class of 57 or so) I used to work with loved this bit of trivia - What’s the fasting rotating tool in common usage? Rifle bullet. On the order of 240,000 RPM in high speed/small caliber bullets. And then he would point out that bullets are limited in rotational speed by the hoop stress factoid above, which limits rotating projectile top speed simply by the needed rotation-speed-for-stability exceeding material strength if you go too fast. It isn’t just that smooth bores aren’t slowed down by dumping energy into rifling – Spinning a properly stabilized bullet limits top rotation speed due to flywheel tress. __________________ Socialism is the myth that two people can live off each other indefinitely without either of them doing any work.
 August 6, 2020, 04:25 PM #22 Bart B. Senior Member   Join Date: February 15, 2009 Posts: 8,927 Yes, hoop stress. First bad one in the shooting industry was shooting Sierra 28 caliber 168 grain match bullets in 7mm Remington Mag barrels. High velocity thin copper jacket bullets well over 3000 fps in 1:9 twist barrels. Obermeyer 5R rifled barrels helped a bunch until Sierra got better copper. A year later, Sierra sent half a lot of 30 caliber 168 grain match bullets to the Army rifle team and the other half to the Navy team. Both teams had bullets flying apart before the 50 yard line shot from 7.62 NATO service rifles with maximum loads. The Army International shooting them in 308 Winchester reduced loads in free rifles used in 300 meter international matches said they were the most accurate bullets ever. Navy got their bullets replaced, Army Int'l team kept all of theirs.
 August 6, 2020, 10:01 PM #23 TX Nimrod Senior Member   Join Date: November 27, 2009 Location: Zona Posts: 421 As stated by others above (years ago!) the solution to centripetal force is a solid copper bullet. Commonly available today, they could be designed to perform well at extreme terminal velocities. But other than an interesting mental exercise - who really cares? . __________________ .22LR - .223 - .22-250 - .243 - 6mm REM - .25-20 - .25-35 - .25 BB - .250/3000 - .257 WBY - .260 - .30 M1 - .300 BO - .30 Herrett - .300 Savage - .32 H&R - .303 - .338-06 - .338 WM - .35 REM - .38-55 - .45 LC - .45-70 - .50-70
 August 8, 2020, 08:51 AM #24 Double K Senior Member   Join Date: June 16, 2020 Location: Colorado Posts: 486 One of my friends who was an engineer at Martin Marietta did some experiments with a 17 Remington to see how fast he could push a bullet. He got over 7,000fps using bullets he turned from solid copper using duplex loads, he also drilled the barrel out removing the rifling.
 August 15, 2020, 10:24 AM #25 stuckinthe60s Senior Member   Join Date: January 31, 2017 Location: Va., Ct., Mo.. Posts: 732 one would think accuracy and dependability would outweigh the need for speed. why so much desire for speed in todays ballistic world? just a novices' question. __________________ Retired Military Aviation Former Member Navy Shooting Team Distinguished Pistol Shot,NRA Shotgun/Pistol Instructor NSSA All American, Skeet/Trap Range Owner

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