Hello,

As I'm nearing the end of my mechanical engineering masters degree, I am entertaining myself with the idea of designing a rifle. Right now I'm trying to see if a piston-operated system akin to those sold commercially for .308 size AR rifles would fit into the concept I'm dreaming of. Of course I'll do the math before putting any prototypes together, but for now, I'm still on the pencil-ruler-paper-level of design, just trying to see what basic layout of the components would fit.

If you have a piston operated ar firing .308-sized cartridges, I would appreciate if you could post some measurements in this thread. If anyone could direct me to something like a blueprint or cad file for a piston system then that would of course also be very much appreciated.


Diameter of the area on the push-rod that interacts with the bolt carrier (i e the area that slams the bolt carrier rearwards).

Diameter pf the piston that gets impinged by the gases.

A simple cell phone pick of the parts would also be nice.

I try to think of some kind of gun pr0n to post in return, but where I am right now, all I have is an old air gun and a set of Primos trigger sticks...

Although the operation is different, the cartridge is the same, thus the forces involved should be the same or similar.  I have an FAL piston on my desk I can send dimensions for if you want

If your vision for a future rifle includes a piston design inside a bullpup chassis, that also has multi-caliber / barrel swapping capability, chambered .308, 6.5 Creedmoor, 260 Remington, you can take my downpayment now.