[quote
For what it is worth try and avoid the mercury recoil reducers. I say this simply because mercury is generaly not allowed on aircraft without special permission. Go with the tungsten idea or try the following link. I believe he ships internationaly and they do work.
http://www.progressiverecoilreducers.com/

thanks, I dont know that they not allowed mercury in planes. could it work as an explosive?
whatever, mercury is out now!
interesting link and it dont look like rocket science

free floating weight balance bei springs