I’m not super familiar with firearms and usually only see them in video games. I notice that pistols and sub machine guns use something called blowback to load the next round from the magazine. My understanding is that the recoil of the round pushes the bolt back and ejects the bullet. This works for pistols and submachine guns like a Glock or MP40.
For rifles though, they have to be gas operated or put in a separate tube so that the gas can go backwards to push the bolt back. Why is this the case? Why can’t rifles like the M16 or AK47 simply use blowback and let the recoil of the gun push the bolt back and load the new round?
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In a straight blowback gun all the recoil forces will be transfered to the bolt. So the bolt gets propelled very fast backwards against the main spring and eventuall crash into the rear of the receiver. If the bolt goes too fast it is going to break stuff. Maybe not right away but it is going to weaken the receiver and eventually crack it. The MP40 only gets away with it because the bolt is very heavy so it does not get much speed. The modern MP5 is very comparable using the same ammunition and same muzzle energy but is much lighter because it use a lighter bolt with a roller delay mechanism. So most of the recoil energy is transfered into the trunion and then receiver as the powder is burning and only some of the recoil energy is used to accelerate the bolt backwards.
In a straight blowback gun all the recoil forces will be transfered to the bolt. So the bolt gets propelled very fast backwards against the main spring and eventuall crash into the rear of the receiver. If the bolt goes too fast it is going to break stuff. Maybe not right away but it is going to weaken the receiver and eventually crack it. The MP40 only gets away with it because the bolt is very heavy so it does not get much speed. The modern MP5 is very comparable using the same ammunition and same muzzle energy but is much lighter because it use a lighter bolt with a roller delay mechanism. So most of the recoil energy is transfered into the trunion and then receiver as the powder is burning and only some of the recoil energy is used to accelerate the bolt backwards.
They can be blowback too
FAMAS and G3 are blowback (with a mechanical delay mechanism)
There is nothing stopping this.
I don’t know enough about the subject to explain why the design choices are made, but blowback can be found on larger automatic firearms. Even cannons, too, like 30mm.
They can be blowback too
FAMAS and G3 are blowback (with a mechanical delay mechanism)
There is nothing stopping this.
I don’t know enough about the subject to explain why the design choices are made, but blowback can be found on larger automatic firearms. Even cannons, too, like 30mm.
It would not be good for the rifle. The impact damage over a long period would probably lead to malfunctions and damages.
Remember most rifles are designed to be used by soldiers, operating away from home base under terrible conditions. A rifle has to be reliable even after thousands of rounds have been put through it. If it is isnt, the rifle is pointless.
It would not be good for the rifle. The impact damage over a long period would probably lead to malfunctions and damages.
Remember most rifles are designed to be used by soldiers, operating away from home base under terrible conditions. A rifle has to be reliable even after thousands of rounds have been put through it. If it is isnt, the rifle is pointless.
It’s an issue of inertia and pressure. In a blowback firearm, the inertia of the bolt needs to keep the case chambered long enough for the pressure to drop to a safe level before extraction. With pistol cartridges like 9×19, that’s relatively easy to do, and the bolts don’t need to be too heavy, usually no more than a pound at most. With rifle cartridges, it becomes more difficult. You are dealing with higher pressures, and heavy bullets moving at several times the speed. In order to keep the case chambered for a cartridge like .30-06, for example, you would need a bolt that weighs several pounds, combined with a very heavy recoil spring. As it turns out, this can be done (see: Thompson Auto Rifle), but the result is a heavy gun with heavy recoil due to the mass of the bolt moving backwards. In the case of the Thompson Auto Rifle, the bolt velocity was so high that spent casings were being embedded in the ceiling of the shooting range they tested it at, since the pressure of .30-06 was so high that it would begin to move the bolt backwards before the pressure had dropped to a safe level, resulting in very high bolt and extraction velocities.
It’s an issue of inertia and pressure. In a blowback firearm, the inertia of the bolt needs to keep the case chambered long enough for the pressure to drop to a safe level before extraction. With pistol cartridges like 9×19, that’s relatively easy to do, and the bolts don’t need to be too heavy, usually no more than a pound at most. With rifle cartridges, it becomes more difficult. You are dealing with higher pressures, and heavy bullets moving at several times the speed. In order to keep the case chambered for a cartridge like .30-06, for example, you would need a bolt that weighs several pounds, combined with a very heavy recoil spring. As it turns out, this can be done (see: Thompson Auto Rifle), but the result is a heavy gun with heavy recoil due to the mass of the bolt moving backwards. In the case of the Thompson Auto Rifle, the bolt velocity was so high that spent casings were being embedded in the ceiling of the shooting range they tested it at, since the pressure of .30-06 was so high that it would begin to move the bolt backwards before the pressure had dropped to a safe level, resulting in very high bolt and extraction velocities.
> they have to be gas operated or..
i dont know much about guns but are there guns that have a gas reserve/cannister for this purpose? (instead of recycling the bullet gases)
> they have to be gas operated or..
i dont know much about guns but are there guns that have a gas reserve/cannister for this purpose? (instead of recycling the bullet gases)
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