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I use a dedicated Spike's upper with an auto-trip. The auto-trip needed to be filed down and the spring trimmed until the timing (when the hammer is released by the auto sear) was correct. It is more reliable with some types of .22lr ammo (like CCI AR Tactical, and mini-mags) than with some others. I'm sure there are plenty of other solutions. This is what worked for me on my Colt 715.
The auto-trip, with an anti-bounce weight is the set of components allowing the .22 bolt to interact with the auto sear on your registered lower. If you don't yet have your registered lower, it might not be a good idea to get those two parts until your stamp comes back. This is not legal advice, just the way I would do it.
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