Item Gone! FS Daniel Defense M4 Carbine (223 cal) AR

[RGRJN]

Somewhere on the barrel it will be stamped with Caliber. Probably under the handguards. The "multi" on the lower is so they don't have to set up a stamp for all the different calibers their lowers go on. Not an expert, but pretty sure you could swap out the lower with any upper, like 300 blackout or 6.8.