Yes, I know there is an AR (or a few of them) from HK.
I didn`t added any pistol grips for the grenade launcher because none of them isn`t fitting.
The slap thing should be on the opposite side, kinda like on the AKs
The MP5AR is a combo of a MP5 and M16/4 (or AR-15)
MP5ARP was made in Pimp My Gun
yumyumshisha has created it [LINK]