Gunsmithing M40A1 build question..

Charlie112

Herd Thinner
Full Member
Minuteman
Feb 28, 2017
709
878
USA
If I build a rifle to fit the title, with the correct parts, can I use the period correct bottom metal if I change the caliber to .223? Possible 20 inch barrel with break, instead of correct 308 barrel length.
Thanks, Charlie112