Broad River Tactical make a handguard for the AR-15 that they call CAR-15. This allows you to use an MP5-SD handguard cover over their handguard. They also make a CAR-15 SD kit that comes with a ported barre like an MP5-SD.
MP5 @ TFB:
I have seen people post photos of CARs that have MP5-SD handguards. Some thin and tube handguards are small enough to allow an MP5-SD handguard cover to slide over. Some even have short barrels and tub a suppressor under the handguard. The CAR-15 is somewhat like that but better.
Broad River Tactical makes the CAR-15 handguard. It is a simple-looking tube handguard with a Picatinny rail on top. It comes with a barrel nut and pan head screws for a flush fit. It also comes with shims to time the handguard against the barrel. In the photo above, you can see the ported AR9 barrel. For those not familiar with the SD porting, the ports are just ahead of the chamber. In an MP5-SD, the ports allow the gasses to vent out and into the suppressor. This bleed-off also keeps bullets from going supersonic and keeps them traveling at subsonic speeds.
I bought the CAR-15 SD kit for $449 on Broad River Tactical’s website. The barrel does not have an indexing pin but it does not need it since the timing of the barrel is not critical since it is still direct blowback.
I was curious how the MP5-SD handguard cover stays on the CAR-15 handguard. Traditionally, the MP5-SD barrel shroud/cage has a lipped flange that holds the rubber handguard in place. Broad River Tactical uses those small brass protrusions that interface with corresponding indentations in the MP5-SD rubber handguard.
The rubber handguard cover does not cover up the entire CAR-15 aluminum handguard but since this it has the SD barrel, the suppressor will cover up the ports.
I used a Manticore Arms CZ Scorpion barrel extension. They were made for the first version of Scorpion Evo pistols when they had 18x1mm threads. I’ve tested this on MP5-SD and it fits and allows the gun to cycle.
I have yet to take this to the range but I am waiting to link up with a friend who has a B&T SD can so I can really test it.
Here is a video on their YouTube page.
Broad River Tactical is working on modifying a CMMG Banshee setup which I hope works great since radial delayed is close to roller delayed and I can imagine that a ported SD version would sound as good as an MP5-SD.
For more information check out Broad River Tactical’s website.