The BCY Mercury is very small diameter, so it takes 32 strands for a spun string (which makes for a very round cross section). 32 times around the posts is a bit much compared with 14 for B55. The BCY 652 requires 20 strands, so it's definitely a fatter fiber, but a bit thinner than B55, for a more rounded string. Once I set the brace height and nock point the Mercury string is as stable as kevlar fiber (well, minus the bow blowup, thank you very much!

). I'm liking the Mercury a lot and will spin one up for the Au Sable longbow, too. Only problem is the color - I've got five 1/4lb spools in flashy Barebow games colors of hot pink, magenta, purple, neon orange, and mountain berry.
Now I've gotta go buy another spool of Mercury in a more tradbow-centric color.
