This is an interesting build by Stein's GBB Build YouTube Channel. He takes the SRU SCAR-L Gas Blowback Bullpup Kit for the WE Airsoft SCAR-L GBB and goes a bit further in making a SCAR-L GBB Bullpup. What he did is convert it into an HPA Blowback SCAR-L Bullpup and it's fun to watch. If you want to do the same, it's fully documented at his Facebook Page.