Old Swiss champ didn´t work, scissors could be dull since I´ve used them a lot.
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Of the MTs I've tested, here are the ones that I thought did great for 550. Gerber MP400, Victorinox Spirit X, Leatherman Micra, any 58mm Victorinox, Style CS.Here's a link to the test thread. 550 was one of the specific things I tested. My criteria for 'pass with distinction' for 550 was cutting the whole strand cleanly with one snip.http://forum.multitool.org/general-tool-discussion/scissor-test/
There are a few folks here that I'd say are huge Gerber fans. One of the really strong points of them (for me, at least) is the scissors. It sort of makes sense since they're part of Fiskars, a company known for good scissors.
91mm Vic scissors work pretty good. my compact cuts it clean, Wenger scissors have micro serations