Quoted:
Which one would you buy and why?
I can't decide really...
Which is most reliable in field conditions?
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You're comparing apples to oranges to pineapples!
AR-50 is a great but(what I would call.) heavy "Bench" type of gun. IMHO.
Serbu is a lighter, therefore harder kicking, "Field" type of gun. Hey! I own one I know! It's a great shooter, but I wouldn't want to be putting lots of rounds downrange each day with it!
Grizzly is kind of between the two, but closer to the Serbu than the AR-50. Also a nice gun.
What I'm trying to say is that You need to know "What" You want the gun to do!?! Is it a target gun? Bench shooter? Are You going to want to walk around with it or set it up and shoot it from a bench? Is cost the main factor or is accuracy Your prime goal?
I own both the Serbu BFG-50 and a State Arms Knob Creek 2000. One of each Type of gun, (IE: Serbu is #25 and portable, State Arms is #41 1/2 and a bench baby.) I can shoot the State Arms all day, as it is almost like shooting My AR's, the Serbu is like a Mag shotgun. Figure out what You want to "Do" with the gun, then drop Me a line if You need more info.
Tall Shadow