what calibers are available to fit AR15/M4 lowers? I’m interested in the .204 ruger but would like to know all the available options…(I currently have 5.56 and 22lr) 
Seriously? Use the search button or Google. This has been discussed ad nauseum.
what calibers are available to fit AR15/M4 lowers? I’m interested in the .204 ruger but would like to know all the available options…(I currently have 5.56 and 22lr)
Seriously? Use the search button or Google. This has been discussed ad nauseum.