You have your IM shut off.
I have a 1 piece 30mm Armalite clone made by promag. It is hell for stout and I think a little better than the real Armalite I have. It has 4 top screws per ring instead of 2. It uses steel thumb nuts for the clamp instead of knurled knobs.
You can see a pic on this page: http://www.promagindustries.com/accessories.asp
It's about half way down.
It's brand new in the box, I never mounted it. I'll take $45+shp. MO or paypal+3-1/2%.