Mjacobs,
The omer mech will work on the RA barrel with modifications, as with Im sure the buechat. The problem is youll need to find a suitable coupling material, some sort of solid plastic rod.
The ID of the omer mech and the ID of the RA barrel is very similar.
I recently changed out my RA mech with an Omer MB type, while it worked out nicely, it didnt match as well as I had planned.
With a little American Fix all (duct tape) it had turned out to be very acceptable. I used a piece of high density plastic rod with an one inch diameter (25mm) to match the two, female to female.
Only the ID of the RA barrel and the ID of the Omer was probably a little closer to 26 mm (ish). So I wrapped a piece of duct tape around the plastic rod and tapped it into place with a light finishing hammer. First into the mech and then the into the barrel.
With self taping screws through the barrel into the rod and in the rod through the mech it is very snug, albeit not quit as tight as the original RA mech.
You could pick up a mech via ebay on one of the smaller euro guns to keep cost down.
Or if your interested i would part with my old RA mech for $50, sorry for the amount only Im looking to cover the cost of a new Aimrite open muzzle for my New Hybrid I recently purchased.
Let me know if your interested, bear in mind that the safety has been removed from my RA mech.
Anthony
Tampa