Just got a B/C from someone and the carrier looks like a FA from the pics I've seen.    It has the longer, equal length lugs, and a "J" on the side.  The Bolt is marked "MPC."  Any ideas?

The "J" stamping on your carrier is the govt code for J.C. Manufacturing, a mil-spec supplier.

The MPC marking on the bolt denote that it was magnetic particle (Magnaflux) inspected and that it was manufactured by Colt after Nov. 2001.

HTH

Quoted: The "J" stamping on your carrier is the govt code for J.C. Manufacturing, a mil-spec supplier. The MPC marking on the bolt denote that it was magnetic particle (Magnaflux) inspected and that it was manufactured by Colt after Nov. 2001. HTH

Ummmm, then how come the original bolt on the brand new SP1 Colt I bought in 1978 is marked MPC?

All Colt bolts since about 1976 have been marked MPC.  Before that, when Colt was the only manufacturer, they were simply marked MP, and the earliest chromed bolts, for the original Air Force contract, were marked M.

Quoted: Quoted: The "J" stamping on your carrier is the govt code for J.C. Manufacturing, a mil-spec supplier. The MPC marking on the bolt denote that it was magnetic particle (Magnaflux) inspected and that it was manufactured by Colt after Nov. 2001. HTH Ummmm, then how come the original bolt on the brand new SP1 Colt I bought in 1978 is marked MPC? All Colt bolts since about 1976 have been marked MPC.  Before that, when Colt was the only manufacturer, they were simply marked MP, and the earliest chromed bolts, for the original Air Force contract, were marked M.

My bad!

Actually I should have included the fact that Colt bolts manufactured before September 1995 (and after the "MP" marked bolts) were also marked "MPC". Colt military bolts made from Sept 1995 until Nov 2001 were marked with a fourth letter  - example MPBC - to denote the month and year of their manufacture. Colt discontinued this system and went back to using MPC after Nov 2001. Sorry if I caused any confusion.