telescoped bolts, trunion placement and free-floating

[PercyShelley]

Hypothetical question:

On SMG designs like the uzi with a telescoped bolt, the barrel is attached to the receiver (with a nut as I recall) about halfway along its length.

Would this made the barrel effectively stiffer? Assuming that the rest of the length is free-floated (don't recall how uzi handguards work), the length of barrel that is allowed to vibrate is much shorter. Sure, the breach-ward section of barrel can vibrate, but this may be less important than vibrations on the muzzle end of the barrel. Furthermore, splitting the barrel into two vibrating cantilevers may reduce the maximum amplitude of the vibrations compared to a single long cantilever.

 

[Shear_stress]

Sounds like every rifle with a barrel band. It may constrict the barrel in one mid-length location, but now you've got two different barrel harmonics to tune for, not to mention the hoop stress that you've created (and which will vary with barrel temp).

 

[PercyShelley]

It's sort of like that, but not really.

As far as I can tell on such designs, the breach end is free-floating, or at least it could be. The barrel is attached to the receiver about halfway down its length.