I set up this full size HK USP for suppressor use. A Jarvis threaded barrel and HK suppressor sights added $400+ to the cost of the gun. These hold 12+1 and are pretty big but only weigh 28oz.
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This is a Glock 20 (21 would be exactly the same) outfitted with after market suppressor height sights - the KKM threaded bbl is on another G21.
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S&W made a suppressor ready M&P 2.0. If still available, this would be the most cost effective way to go.
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M&P with long version of Rugged Obsidian suppressor
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HK with "short" option Rugged Obsidan
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The rugged obsidian suppressor has a screw on extension that makes it approx 2" longer when attached. The longer option is supposedly quieter - the shorter option is handier.
All of these make for fairly large rigs with the attached suppressor.
If avail on the model you choose, factory threaded barrel and suppressor height sights will be more economical.
FWIW,
Paul