Here are some I have made.

I am experimenting with design and materials. Thanks to Jim for the help. He has kindly done some mag dumps and we tested temps with an infared laser thermometer. We had no problem with 4 back to back mag dumps (5.56)

The short one in the picture is Jim's, because his is much shorter than mine.

None of these need to be cinched on. I built a roll into the barrel end to keep it in place during recoil.