Four things people get wrong after they've already bought
Thread pitch, subsonic margin, overall length, total cost. Each of these has an answer that is arithmetic, and each of them is expensive to discover late.
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Subsonic margin
Whether your load stays under Mach 1 at the temperature you're actually shooting in, and the temperature where it stops.
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Thread pitch matcher
Direct thread, adapter, or incompatible — plus the bore rating check that prevents baffle strikes.
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Overall length & SBR check
Where a suppressor puts you against the 16-inch and 26-inch federal thresholds, drawn to scale.
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Setup cost builder
The whole figure — host, barrel, mount, can, dealer fee — with the $200 saving shown as the proportion it really is.