I have had the 550 for a long time. It required dis-assembly and cleaning to get it going again, but it's working fine now.
Member: Orange Gunsite Family, NRA--Life, Varmint Hunters' Assn., ARTCA, American Legion, & South Cuyahoga Sportsmen's Assn.
Caveat Emptor: Cavery Grips from Clayton, NC. He is a ripoff