Can two bullets occupy the same barrel...?

[Kirk Freeman]

Sure, duplex ammo.

 

[buzz815]

Back in the Vietnam era I seem to recall shooting piggyback rounds in .308. They were designed to hit about 3 feet apart at 100 yds. They were not very accurate but put twice the amount of lead on the enemy.

 

[Kirk Freeman]

M198.

 

[jblomenberg16]

Wouldn't a large portion of those gases be purged when the bolt opened for ejection?

Good point...looks like my brain was already shut down last night when I posted. I've had my morning coffee and see the error of my ways!

 

[dak109]

RNM, just coming down from NFA Day? I am still smiling!

 

[singlestacksig]

H&K made a caseless assult rifle that could fire a three round burst that may have had 2 bullets in the barrel at once..

 

[ckcollins2003]

H&K made a caseless assult rifle that could fire a three round burst that may have had 2 bullets in the barrel at once..

If you're talking about the G11, the rate of fire is extremely fast at 2,000rpm, which means it fires 33.33rps, but the muzzle velocity is 3050 ft/s and it only has a 21.25 in barrel. After doing the math, you'd need a 91.5 ft barrel because the rounds are going so fast.

Now, if it shot a .45 cal at 750 ft/s, you'd only need to add 1.75" to the barrel and you would have 2 bullets in the barrel at once. And that sounds exciting!

 

[bluto67]

the hk g11 fired a 4.73x33mm caseless round and was "very advanced but overly complicated". the g11 never reached production due to a number of issues, issues not stated in the article. only 2 companies have ever produced a hyper burst rifle. hk and izhmash with only izhmash producing a model that went into limited production that was issued to select russian special forces units. thank you shotgun news.

 

[CalebToNowhere]

Sounds like a job for myth busters or red jacket to me. Maybe that's why they use multiple barrels on chain guns in addition to keeping the barrels from melting.

I don't know. Red Jacket would just put 4 barrels together and then blow it up with pyrotechnics. I think Myth Busters would be more appropriate.

 

[kludge]

First off, if you open the breech to load the second round your going to lose all your pressure, so the bullet might not even exit the barrel, just from bore friction slowing it down...

At any rate you DO NOT want the breech to open when there is any pressure in the barrel, for safety reasons obviously.

Now then, for starters let's assume that a .308 Win bullet spends 1.5ms in the barrel. (Pretty standard actually). That would be a theorectical max cyclic rate of 666.7 rounds per second -- meaning that at the exact moment the bullet left the barrel, there magically appeared another round in the chamber that instantaneously fired.

That's 40,000 rounds per minute. IOW... not happening. If you watch slow motion video of a machine gun, the breech/bolt/whatever can't come close to cycling fast enough to get anywhere near that number, the bullet is long gone from the barrel and the bolt has moved only a mere fraction of an inch. The bullet is halfway down the barrel when it passes the gas block, then the gasses have to start pushing on the bolt or op rod, all of which is much much heavier than the bullet and then it's just and F=ma thing. The bolt/op rod has much more mass than the bullet.

The world's fastest machine gun is 1,000,000 rounds per minute from 36 barrels. The ammo is stacked in the barrels, not individually loaded cartridges, so that's 27,778 rounds per minute from each barrel. Granted it can't do that for very long.

http://www.youtube.com/watch?v=xe-QP8s1ZJc

 

[cbseniour]

Gattlin gun,
Can't have two in a barrel at the same time but if you rotate the barrels you can fire a quickly as the action can cycle.

 

[Mr Evilwrench]

No. If the bullet is moving slowly enough, and the barrel is long enough, it might be possible for the action, if it's very fast indeed, to cycle before the first bullet has left the barrel. However, you'd be pulling the shell out of the chamber under pressure, which will result in a huge blast out the breech. The bullet won't stop, due to momentum, but it will start slowing down. If the action (remember it has to be very fast) can then fire the next one before the first leaves the barrel, it will start catching up. As long as this cycle continues, you'll have some nice, slow, marginally accurate bullets up to the last one, which will likely catch up and rear-end its predecessor. Plus you'll get all those breech blasts in the face, which is a lot of wasted energy. Even that hyperburst just games the mechanism to get the second round downrange during the first recoil; 27m is pretty far past the length of the barrel. In other words, you might be able to do it, just to say you had, but you'd have to go to such great lengths, and so compromise your performance, that it would have no practical application.

 

[XtremeVel]

Sure, duplex ammo.

Inaccurate, but I would think that would place (2) in barrel at same time.

Back in mid 80's, guns and ammo did feature a article about handloading this using (2) Sierra 90 gr .355 dia bullets stacked in a .357 mag case.

Remington also made a factory load using (2) 70 gr 000 buck, also in .357 mag...

 

[Mr Evilwrench]

But a duplex is essentially the same thing as a shotshell, and that's been disqualified.

 

[243rem700]

All of the calculations so far have longer times in the barrel than posted. The velocity is not constant in the barrel, but rather acceleration is occuring. The muzzle velocity is only the velocity at the muzzle, increasing time in the barrel since the bullet is not moving at powder ignition.

It still is not possible to have 2 bullets in the barrel with any technology that we have today. The closest thing would come from caseless cartridges.

 

[bluto67]

All of the calculations so far have longer times in the barrel than posted. The velocity is not constant in the barrel, but rather acceleration is occuring. The muzzle velocity is only the velocity at the muzzle, increasing time in the barrel since the bullet is not moving at powder ignition.

well of course, but if i were smart enough to calculate the time spent in the barrel from zero velocity to max muzzle velocity i'd probably have a high paying job with the space administration designing wicked star fighters or something else cool. sometimes you just gotta leave out the varibles and go with what you got.

 

[redneckmedic]

It still is not possible to have 2 bullets in the barrel with any technology that we have today. The closest thing would come from caseless cartridges.

I think the debatable part of this isn't just can two bullets be in the barrel, but they have to have independent propellent systems to actually have a talk worthy discussion. IDK the actually outcome, however just having one discharge with two projectiles kinda defeats the purpose of the OP.

 

[H.T.]

About 25yrs ago the Army reaserch people came up with a rifle.
Based on the M16 system. It used a round that had 2bullets, the nose of the
second fit into the rear of the first.

 

[kludge]

I think the debatable part of this isn't just can two bullets be in the barrel, but they have to have independent propellent systems to actually have a talk worthy discussion. IDK the actually outcome, however just having one discharge with two projectiles kinda defeats the purpose of the OP.

The stacked rounds/charges in the machine gun vid that I posted is done by stacking charge/projectile/charge/projectile/charge/projectile etc., and the charges are set of by computer.

It only works as fast as it does because you don't have to spend any time to open the breech and insert another cartridge. The time the projectile spends in a typical rifle barrel is on the order of 1.5 milliseconds. This is known, it doesn't have to be calculated (to bluto67's point) just look at some pressure traces.

If you wait 1.5ms to set off the next charge you get the rate of fire talked about in the video. They aren't quite getting 40,000 round/min, but it's close.

So even at that rate, there is very likely only one bullet in the barrel at any given time.

 

[Yeah]

The velocity is not constant in the barrel, but rather acceleration is occuring.

Neither is pressure.

A person doesn't have to calculate transit time in a barrel for a given setup, or pressure versus time/distance, as there are some software packages that will do all that. Quickload provides those charts upon request.

I don't know of anything that will simulate two bullets occupying the same barrel, but given the above the math wouldn't be all that difficult. You'd simply need to consider the effect of the pressure left from the first bullet on the pressure curve of the second, since it would be going under non-normal atmospheric conditions. Of course after the second bullet fired the pressure curve of the first's would be modified, which could get complicated if its powder was still undergoing combustion. But a faster powder would be preferred there.

Other than unequal pressure at the breech end, not altogether different from the math for all those "Can I shoot my Glock underwater" threads that made the rounds.

You'd need to be sure that modified pressure curve didn't exceed the capacity of the system.

And that the increased pressure didn't do anything odd with the bullet's obturation tendencies.

And probably some other hurdles I'm not considering.

I'd be confident in the math, but I don't own anything that can get another bullet going before the transit time expires, so I won't be testing it.