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.

This example uses the CMMG rotary-delayed blowback action, and EndoMag 9mm magazines in regular 5.56mm Pmag bodies. That means the whole system works with a standard AR lower, instead of needing a dedicated pistol-magazine lower. The silencer is a clone of the H&K SD type made by HiTec Arms, and it is a fantastically quiet combination!

Disclosure: Broad River Tactical send me the upper for free, and I put it on an SBR lower I already had. I bought the silencer. I have no other relationship with BRT or HiTec Arms.