5fps doesn't sound too bad, not perfect but good enough.
could be the preload difference compared to whatever you had it in previously, say a shorter box with thrust bearings on spring guide and piston compared to only one here.
i'm guessing by the targets you're going for this is going to be a dmr platform, and the titan suggests precocking, in which case having thrust bearings on both ends isn't the worst option (i tend to avoid running piston bearings on auto guns to save piston weight/avoid pme but that's not relevent in a semi-only pew)