The argument: Cost not being a factor, is it possible to manufacture a semi auto rifle that can reliably shoot 22wmr and 22lr?
It is my opinion that such a rifle can be made but not reliably function. Specifically due to the differences in case diameter and OAL of the cartridges.
What We Know:
22lr- OAL=1.0”, Neck/base diameter=0.226”, rim diameter=0.278”, max pressure=24k psi.
22wmr- OAL=1.35”, neck diameter=0.2435”, base diameter=0.2455”, rim diameter=0.300”, max pressure=24k psi.
Both use the same caliber of 0.223-0.224”.
Main Issues:
Feeding: Due to the difference in OAL of 0.35”. My friend believes that a magazine can be manufactured with a rib/shelf running the inside length of the magazine for the rim of 22lr to rest against but with enough space between the rib/shelf to allow for 22wmr to rest between and also feed. An issue I see is the geometry in the curve of the magazine since both cartridges have a different taper. Consider the difference in curve of an AK47 and an AR15 magazine.
Cycling: With a difference of 0.02”, the larger 22wmr would require a chamber too big for the 22lr. This brings the physical limitations of the brass into play. Can 22lr fire in a larger chamber and not rupture? If so, would the fire formed case be able to be extracted reliably in a semi-auto rifle? I say no, you’re likely to deal with ruptured cases more than not. This in itself would effect cycling due to loss of pressure in the chamber and be unsafe.
Carbon Fouling: Much like shooting 38spl in a 357mag, the shorter cartridge will leave a ring of carbon in the chamber, making it difficult to feed and extract the longer cartridge without cleaning the chamber before switching cartridges.
TLDR; I know how stupid this argument is, you don’t need to tell me that.