Crazy idea for a rifle design...

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grampajack

grampajack

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I've been reading a lot lately about last ditch weapons, and I'm wondering if anyone has ever tried a blow forward rifle that fires from an open bolt (uh...open barrel, I mean:scrutiny:).

I'm thinking a heavy(ish) profile barrel might actually have enough mass to allow for simple blow forward (i.e. no locking breech mechanism) for a rifle cartridge, or at least something similar. Perhaps it wouldn't allow for true 50-70k psi rifle cartridge pressures, but it might come close enough to make a viable assault rifle that was simple blow forward. For example, it might be able to handle .30 carbine.

It would only have two major parts (barrel and receiver) since the barrel would replace the bolt. The firing pin would be fixed in the rear of the receiver. The trigger group would be a simple sear, like what you see on the Sten (obviously this would have to be a bullpup, or otherwise the trigger would have to have linkage going around the magazine well).

I'm really surprised the Germans didn't try it. I'm also surprised that we don't see something like that coming out of countries where criminals primarily use homemade guns.
 
Do you mean like a slamfire gun or something spring loaded and auto loading? I guess I don't see how it would be better or simpler than a blowback pistol caliber sub-machinegun.
 
I actually sort of like that idea! it would have to be heavy, clunky, and probably pretty stiff to operate to keep any highpower rifle cartridge bottled tho. Lock time would also likely be pretty horrendous and movement before the shot might make it very hard to shoot accurately. Probably want to stay with as short a cartridge as possible to keep the lock time down.
If it were a semi, than youd need some way to keep the firing pin from firing the round as the barrel assembly pushed it back against the receiver/bolt.

you might also be able to come up with some form of delayed blow forward action....
 
someguy2800 said:
Do you mean like a slamfire gun or something spring loaded and auto loading? I guess I don't see how it would be better or simpler than a blowback pistol caliber sub-machinegun.
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Semi or full self loading. Well, it would be much lighter, as the barrel would double as the bolt. It would also as a result of that be much shorter. Far less machining, as well.

Also, direct blowback is very limited. Even with relatively low pressure rounds, the bolt must be extremely heavy to keep the chamber sealed long enough. Since the barrel is already a heavy part, taking advantage of that inertia would allow you to have a higher pressure cartridge without having to increase the mass of the bolt to the point where the platform was no longer viable. 7.62 tok is pretty much the extreme end of what direct blowback will practically do, at least when a traditional bolt is used, and they weigh so much you couldn't pay me to carry one.

LoonWulf said:
I actually sort of like that idea! it would have to be heavy, clunky, and probably pretty stiff to operate to keep any highpower rifle cartridge bottled tho. Lock time would also likely be pretty horrendous and movement before the shot might make it very hard to shoot accurately. Probably want to stay with as short a cartridge as possible to keep the lock time down.
If it were a semi, than youd need some way to keep the firing pin from firing the round as the barrel assembly pushed it back against the receiver/bolt.

you might also be able to come up with some form of delayed blow forward action....
Click to expand...

Lock time is always going to be horrendous on anything open bolt. Obviously it's not something that would make a good designated marksman's rifle. But, the weight would be inherently low, as there wouldn't be any bolt or carrier.

The firing pin would be meant to fire the round as it was pushed back into it by the chamber. It would work just like an open bolt SMG with a fixed firing pin.
 
So rather than tripping a hammer with a pull of the trigger, you trip the forward run of a bolt that weighs ounces. No thanks.Years a go I had some junker single shot 12 gauge like a kel tech thing. It fired from an open bolt. I hated that gun, just like all the open bolt guns I have fired.
 
JeffG said:
So rather than tripping a hammer with a pull of the trigger, you trip the forward run of a bolt that weighs ounces. No thanks.Years a go I had some junker single shot 12 gauge like a kel tech thing. It fired from an open bolt. I hated that gun, just like all the open bolt guns I have fired.
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It ain't no Rolls Royce, that's for sure. More like a Trabant.:D
 
Jim Watson said:
Blow forwards.
Coenders - Rochling last ditch German.
Hilleberg carbine, USA.

I think Carbine Williams had one but Google is not helpful.
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I had forgotten about those. The forgotten weapons guy did a neat video on one a while back. Not a blow forward, but it proves that rifle pressures can be well handled by direct blowback.

I think steel cased ammo and chamber flutes would be obligatory, but not a deal killer considering steel cased ammo is par for the course on a last ditch rifle anyhow.
 
I'm wondering if anyone has ever tried a blow forward rifle that fires from an open bolt
Click to expand...

Unless the design is going to tap propellant gasses and direct them back to the receiver to aid in the forward motion of the barrel (which would increase parts count, complexity and utilization of machine tools which are incompatible with "last ditch" type weapons manufacture) then the friction between the bullet and the barrel is relied upon to transfer momentum to the barrel to "blow" it forward.

And since the design is specified to fire using an "open bolt" (i.e. slam fire), the immediate problem becomes one of how rounds are fed from a magazine, how they are held in place while the bolt is at the forward end of its cycle and then ejected?

Since magazine-fed semi-automatic rifles have traditionally relied on using the movement of the bolt/bolt carrier to strip a round from the magazine and feed it into the chamber, switching to having the rifle operate through the movement of the barrel opens up a whole host of challenges in where the energy comes from to strip and chamber the round and whether existing magazines can be used. Again, needing to design, fabricate and distribute a new type of magazine seems incompatible with the purpose of a "last ditch" weapon.
 
hdwhit said:
Unless the design is going to tap propellant gasses and direct them back to the receiver to aid in the forward motion of the barrel (which would increase parts count, complexity and utilization of machine tools which are incompatible with "last ditch" type weapons manufacture) then the friction between the bullet and the barrel is relied upon to transfer momentum to the barrel to "blow" it forward.

And since the design is specified to fire using an "open bolt" (i.e. slam fire), the immediate problem becomes one of how rounds are fed from a magazine, how they are held in place while the bolt is at the forward end of its cycle and then ejected?

Since magazine-fed semi-automatic rifles have traditionally relied on using the movement of the bolt/bolt carrier to strip a round from the magazine and feed it into the chamber, switching to having the rifle operate through the movement of the barrel opens up a whole host of challenges in where the energy comes from to strip and chamber the round and whether existing magazines can be used. Again, needing to design, fabricate and distribute a new type of magazine seems incompatible with the purpose of a "last ditch" weapon.
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Definitely wouldn't work with existing magazines, but the feeding and ejection for blow forward was worked out long ago. Surprisingly, it proved itself to be very reliable. The magazines are different, but they're no more complex than a traditional magazine.

There wouldn't be any need for any kind of gas system. It would work just like a direct blowback, except that the barrel would move and the bolt would be fixed, as opposed to the barrel being fixed and the bolt moving. Of course I'm using the term bolt loosely here. The "bolt" would in fact be the rear portion of the receiver. If you think about a bolt as a moving breech block, then this would simply be a fixed breech block with a moving barrel, as opposed to a fixed barrel with a moving breech block.
 
A blow-forward will have a nasty recoil, period. Someone once made a blow-forward shotgun for testing by the military. After the first shot, the tester handed the gun back to the inventor and told him, "you're going to do all of the shooting...."

If you look at the physics of a blow-forward, what is really happening is the barrel is going to try and stay stationary and the rest of the gun will try and move rearward.
 
lysanderxiii said:
A blow-forward will have a nasty recoil, period. Someone once made a blow-forward shotgun for testing by the military. After the first shot, the tester handed the gun back to the inventor and told him, "you're going to do all of the shooting...."

If you look at the physics of a blow-forward, what is really happening is the barrel is going to try and stay stationary and the rest of the gun will try and move rearward.
Click to expand...

That is more or less correct, but the weight of the bullet is a big part of that. In any case, I don't see how it could be much worse, if at all, than single shot.
 
lysanderxiii said:
A blow-forward will have a nasty recoil, period. Someone once made a blow-forward shotgun for testing by the military. After the first shot, the tester handed the gun back to the inventor and told him, "you're going to do all of the shooting...."

If you look at the physics of a blow-forward, what is really happening is the barrel is going to try and stay stationary and the rest of the gun will try and move rearward.
Click to expand...

This is correct. There will be an equal and opposite reaction. A simple single shot with a locking breech would be better in every way. As a repeater there are plenty of existing designs.
 
grampajack wrote:
Of course I'm using the term bolt loosely here.
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That's fine. I'm following what you are talking about. And I'm not a "magazine" versus "clip" purist. I'm familiar with the Mannlicher 1894 and the Schwarzlose 1908 so I know the technical issues can be deal with.

My point about the magazine had to do with the weapon's role as a so-called "last ditch" weapon. By definition, a "last ditch" weapon (see: http://www.dictionary.com/browse/last-ditch) would be one in which the resources to produce something more complex, more refined, more highly finished, no longer exist or must be devoted to the production of other war materiel. In a last-ditch weapon, priority is given to a low parts count, preference for cast, stamped, pressed, drawn or extruded parts over forged and machined parts. Reduced use of strategic materials (i.e. aluminum, alloy steel, etc.), use of engineering labor is reduced, use of skilled labor in assembly is minimized, the number of assembly steps curtailed and the parts count kept as low as possible as the parts may have to be fabricated in a number of dispersed garage-shops. In an environment where priority is being given to simplicity, speed of assembly and minimal use of machine tools, the need to develop, manufacture and deliver a new magazine to the field to go with the new gun would be anathema since it adds to - rather than subtracts from - development time and imposes additional resource requirements on a manufacturing base that - in a last ditch posture - is already under strain. The fact that in a "last ditch" situation, the savings in engineering, machining and parts count from using a blow-forward design is offset by the need to develop and field a new magazine.
 
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