Raizo_Sekai and I got together this morning to shoot. It's hard to see the recoil impulse difference between the two guns but I think his actually shoots just as soft with his 11.5" barrel. His 14.5" feels softer.

Video.

I have a KAC SR15 E3 IWS upper with a URX III installed and BC 1.0.

He's got a frankengun with a Syrac Ordnance adjustable gas block. It's tuned to lock back on an empty mag with Wolf ammo so it'll cycle anything.

I guess the soft shooting of the proprietary gas system on the KAC can be matched by a well built home brew.