I purchased a EOTECH 557 from a friend (trust friend, so I know it's not broke), however I'm having issues mounting it to my S&W MP15. It won't tighten to the rail, and is really wobbly. Is there a special mount I'm missing to get it to attach? Thanks.
I've tried everything I can think of. I have all the hardware it came with. It's completely screwed in when i turn it, but it just wobbles on the rail.