What if there was no MP5? In this video Forgotten Weapons feature the The CAR-15 SD... "What is the MP5 was never adopted, and instead the vented barrel and telescoping silencer used by the SD model was instead developed for the AR-15? Broad River Tactical thought it would be fun to follow this line of thought, and builds an MP5SD style barrel and handguard system for the AR - and I think it's a very fun and very cool concept.