Requesting help from XM177 owners

A friend is building an XM177E2 clone and is missing the grenade ring. I hope to machine one for him but have no idea what the dimensions are. Would one of you kind folks be able to provide the necessary dimensions to me? A PM is fine. Thank you!
Marty
BCE

http://www.gunbroker.com/Auction/ViewItem.aspx?Item=218634903

Try contacting this vendor - he’s got a good reputation for making both reproduction grenade rings and moderators.

Thank you! I just received his email response and he has the parts I’m looking for. I appreciate the help!
Cheers,
Marty