This is kinda funny.....
 

Took the brand spanker new Model 1 upper to the range....Feeds supersonics like a dream..wouldn't feed sub for didly...I ended up clamping a chunk of innertube over the muzzle with a hose clamp.... subsonics fed very reliably untill the rubber got too blasted away ( usually about 5-6 shots) Sooooo... Tomorrow we get a chunk of 7075 and spin up a Noveske-esque, brake/ flash hider to try and give this turkey enough back pressure to feed subsonic loads without issue, the things you do to save a few scheckles.... Of course I could go for some heavier blast resistant rubber:rolleyes:

Is that safe shooting with a rubber over the end of the muzzle? Or is it just one of the AIDS barriers? (Action In Distress Stoppage)

I dropped a Wolff reduced power recoil spring in my new AR when playing with subsonic loads. Feeds like a dream after that!
geichal

One never knows what wonder will work like a dream. I am very happy for you. One more possible solution logged.