I already own a Colt 20" HBAR A2 using iron sights, and im now looking to get a shorter barrel M4. Im not crazy about red dot scopes, so does anyone use a traditional scope on their M4? I know the M4 is really for shorter distances than the A2, so Im not sure using a scope would make alot of sense. Can you guys recommend a good optic for an M4? Thanks.