25 Grendel or 25 BR

[grayfox]

Simplest way I can think of is to find someone who can 'cnc an upper/lower set, call it a "stretch-15", add maybe 0.2-0.25" to overall length via longer magwell up through the lower/upper/carrier and CH, lengthen the buffer by the same to allow the bcg to cycle. Maybe even widen the lower what, 0.2" again to allow for polymer mags... or keep it same width and use a single-stack or a "1.5 stack".

All things considered you should be able to leave the metal/finishing/material qualities the same -- seems like this would be an incremental upgrade that seems possible.