Screw delayed blowback firearms

[Cutaway]

Would it be possible to make a screw delayed blowback rifle?, its just that on another forum some users say that a few prototypes that used this operation would have been more reliable if the barrel used a fluted chamber.

The weapon would probably look like this:

 

[Jim Watson]

The only one I know of is the Thompson Autorifle of 1923 which used a screw thread bolt allegedly retarded by the Blish Principle, which is not really very - if any - effective. The article below mentions a couple of SMGs of similar operation but that seems wasteful what with all the plain blowbacks in use.

http://www.forgottenweapons.com/ria-thompson-model-1923-autorifle/

 

[HiBC]

Funny!! I took the title of your post as a comment on delayed blowback firearms!.

I was interested in reading more.

 

[dakota.potts]

I don't see it working by acting directly on the screw. If the bolt acted on a cam mechanism where it had to draw so far back before it started to unlock it might work, but I see it as needlessly complicated. Obviously short recoil systems and roller delayed blowback systems have been effective. Lever delayed blowback systems (the FAMAS) have worked but generally have their share of drawbacks. I have even seen a delayed blowback using a rotary mass in the bolt. I guess my question would be what would the system solve?

 

[kozak6]

Kalashnikov designed one, but it never went anywhere.

Delayed blowback firearms can have issues with case head separation since extraction begins immediately upon firing. A fluted chamber helps mitigate this.

 

[barnbwt]

I would suggest looking up a topic called "moment of inertia." Fact is, a rod spun about its axis doesn't absorb a whole lot of energy/momentum/etc in so doing. Not compared to spinning it perpendicular (like a baton) or even reciprocating it back & forth like a piston. The reason is because the metal at/near the center of the rotation doesn't actually rotate much, so the effect is nearly identical to spinning a hollow tube of lighter mass.

So if you're going to accelerate a bolt mass to make it absorb more energy over a given distance so the bolt can be lighter for a given cartridge, it makes the most sense to spin it orthogonal to its length, and reciprocate it, in that order (there's a weird little piston/crank Mauser SMG that sort of works like this).

The layout of your concept gun looks cool, but the mag appears to be 223 or even 308 type rifle cartridge length; I'd cool my aspirations to pistol cartridges first to feel out the effectiveness of these ideas before pursuing them in such high powered options --you can't afford to be "close" with that kind of juice, and delayed blowback is always a dance with the devil, no matter how you go about it.

Another route might be to make the action recoil operated; most delayed blowback systems like the FAMAS or CETME actually started out as recoil-operated formats (Federov and MG42 if memory serves), and a screw-delay turned into a recoil-op locked breech is what we call "rotating bolt" lockup and highly reliable, so it may be possible to work it into a blowback with careful design & development.

TCB

 

[Cutaway]

The only benefit would be simplicity. The operation may work well with the mentioned fluted chamber and using intermediate rounds/shotgun rounds, other than that it looks dodgy to fire.

 

[dakota.potts]

I'm not so sure it does have an edge in simplicity over other systems. There are some very simple semi-automatic locking systems out there. The CETME/HK series of roller delayed blowbacks are fairly simple (in theory, the geometry they had to work out had some complex math) and come apart into just a few major groups. Other semi auto rifles such as the SKS, AK, and FAL also have pretty simple locking mechanisms. At least, simple in comparison to the complication of machining a screw-delayed bolt.

Of course, if simple is what you're looking for, there's always this prototype blowback .308