I've checked them out quite a bit and am an "Ambassador" for Fusion Firearms. Though I do not yet own a single product. It's only been 8 months, so maybe they just need a little time

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Mixed reviews from the ones I've seen at matches. I know of a few where the comp or mono block flew off and the barrel mounting lugs broke. Fusion has apparently changed the design in hopes to fit it and claim it was a heat treat issue for some barrels.
For the most part they seem to work as good as most other firearms, at least according to the folks that I know personally that have shot them. Recoil is very flat as they are heavy guns with a big ol comp hanging off the front of the barrel.
One of these days Fusion will possibly think about supporting their "Ambassadors" and getting some product into our hands. Until then I can only go by what I see and what those that I know say.