I'd been looking at those, but what really bothers me is that the rail on the top of the receiver doesn't align with the rails on handguards. A company up in Canada did a similar thing, only they did it right:
http://www.fabsports.ca/STOCK/fs556/fs5562.html
There's a thread about it on Rimfirecentral:
http://www.rimfirecentral.com/forums/showthread.php?t=242051
http://www.fabsports.ca/STOCK/fs556/fs5562.html
There's a thread about it on Rimfirecentral:
http://www.rimfirecentral.com/forums/showthread.php?t=242051