Anyone use Copper plated Berry's 150 gr. in an AR 300 Whisper?

[hovanr]

I've been able to get them to feed using M4 ramps that I made a little wider with the dremel. I have only tried Pmags with them though. I'm trying to make it run on a 7" barrel and have been able to do so with about 15grs of 1680 and a wide open port. I think I'll be trying what mak91 did and go with a gas tube shorter than pistol length to see if I can get it to run subsonic with pistol powders. I'll post results at a later date.