recoil of the weapon would force a small piston to pump cooling media through a series of coils around the machine gun barrel, to a radiator(perhaps mounted under the barrel) then back to the piston pump. the system would be ideal for high ROF weapons that you wouldnt want to change barrels on often, like coax guns on tanks.
-- bobenhotep, Apr 01 2004

Nice idea, so croissant, but is it practical?
-- DesertFox, May 04 2004


Don't alot of guns use the recoil to chamber the next round?
-- MikeOliver, May 04 2004


the ammount of recoil used to operate the weapon is negligible, in the case of an m2 50 cal
-- bobenhotep, Jun 30 2004


Even pistols like a 9 mm Parabellum only use part of the recoil to chamber the next round so there is plenty left to operate a cooling pump. Here is a rapid firing bun for you.
-- GenYus, Jun 30 2004


There is the issue that this will reduce the power of the weapon, but all automatics make that sacrifice anyway.
-- 5th Earth, Jul 01 2004


I'd be pretty susceptible to the powers of suggestion if I was looking down the wrong end of a .60 cal.
-- contracts, Jul 01 2004


wouldn't this cause very rapid changes of heat which may be damaging to the gun's material. I realise guns are capable of withstanding high temperatures but what about going from low to high and back again so quickly? someone do some math or something.
-- etherman, Jul 01 2004


[Tabs]: The correct terminology would be co-planer. The idea of a coaxial weapon on a tank is that there is a machine gun pointing wherever the main gun points.

[etherman]: Actually, this invention would reduce the temperature swings that the gun goes through. When you first fire a gun, it is going to heat up fast. With a water jacket, it isn't going to heat up as fast.
-- GenYus, Jul 01 2004


coax is short for co-axial, and is tank crewman slang for such a weapon
-- bobenhotep, Jul 02 2004


this system , if powered by the recoil of the weapon, would have a negligible effect on the muzzle velocity , but would "soak" up the weapon's recoil.
-- bobenhotep, Jul 02 2004


I am fairly (make that really) naive about this kind of thing but it seems to me that a better source of energy to power a pump would be from the gas generated by the firing. I'm guessing that, in order for there to be good accuracy from the weapon, the bolt, or receiver, or whatever holds the cartridge in place in the action, must remain locked up for some period of time after the primer has been struck--at least long enough for the deflagration to begin and for the case pressure to rise to the point where the projectile breaks the seal and begins its transit from the cartridge.

During the lockup period, I'm guessing that a large percentage of the recoil energy is transmitted from the face of the bolt to the receiver and to the frame of the weapon. The only way I can see to recover this initial energy is to allow the entire receiver or frame sub-section to move and to use that motion to drive the coolant pump. After the lockup ceases, the gas in the barrel pushes the bolt back to expel the spent cartridge and the remainder stored in a spring for the chambering of the next round (if the weapon fires from an open bolt [don't most fully automatic weapons?])

In a gas-driven scenario, a port in the action, or barrel base, can be opened and allow gas to be siphoned off from the column behind the projectile to power the coolant pump but without any elaborate receiver or frame suspension mechanism. Further, the port timing could be varied depending on the need for cooling on a per shot basis.

As in the recoil powered scheme, compensatory amounts of powder could be added to the round to offset the losses used for cooling.
-- bristolz, Jul 02 2004


Actually, [bristolz], until the bullet leaves the casing, there isn't any recoil. The recoil is the "equal, opposite" reaction to the action of accelerating the bullet down range.
-- GenYus, Jul 02 2004


Of course.
-- bristolz, Jul 02 2004


[Genyus]: The recoil is not just the bullet, but also a certain percentage of the reaction mass (gunpowder) that propels it. Think muzzle flash--some of that stuff is shooting out the front like a rocket. But this is just a nitpick.
-- 5th Earth, Jul 02 2004


//I'm guessing that, in order for there to be good accuracy from the weapon, the bolt, or receiver, or whatever holds the cartridge in place in the action, must remain locked up for some period of time after the primer has been struck--at least long enough for the deflagration to begin and for the case pressure to rise to the point where the projectile breaks the seal and begins its transit from the cartridge.//

The issue isn't accuracy so much as safety. If the action is opened too far while the bullet is still in the barrel, the pressure will blow out the side of the fired casing causing shards of hot metal and high pressure gasses to go where they shouldn't.

Many small-caliber pistols, and rifles chambered for pistol calibers, use what's called "blowback" operation. The action is held closed by a spring; the force of the spring and mass of the action are sufficient to prevent the action from opening too far before the bullet leaves the barrel; at that point, the action will have enough momentum to cycle the rest of the way.

Blowback operation is simple, but use with large cartridges requires that the action be quite massive and generally also requires that the recoil spring be quite stiff. In a rifle chambered for something like .45acp, the mass of the bolt is not objectionable; in a .45 pistol, however, the slide would be annoyingly heavy (Hi-Point makes a blowback-operated .45 pistol; the thing looks and feels like a brick).

In pistols, the most common alternative to blowback operation is recoil operation. When the gun is fired, the barrel and breech start out travelling rearward as a unit. After they have moved together for about 1/4", the barrel unlocks from the breech and stops moving; the momentum of the breech assembly will be sufficient to complete the cycle. In some designs such as the 1896 Mauser or the Luger, the barrel slides straight rearward; in most newer designs, the back of the barrel cams downward.

Recoil operation works very well for pistols, but having the barrel move relative to the frame makes it hard to achieve perfect accuracy. Most handguns are designed for use at short ranges, so this is not a problem. Trying to construct an accurate rifle with a sliding barrel, however, would be rather difficult and is not often done. Indeed, even shotguns seldom use sliding barrels (some older Brownings did, but I think the design was abandoned).

Most auto-loading shotguns and rifles (and a few pistols like the Desert Eagle) use gas operation. When the bullet or shot passes a hole in the barrel, gas goes through that hole and pushes on a piston. This in turn pushes on a "bolt carrier" assembly which unlocks the bolt and moves it rearward. Gas-operated mechanisms are a bit bulkier than recoil-operated ones, but in a rifle or shotgun that's not a problem.
-- supercat, Jun 02 2006



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