For one thing, many of the issues have been touched on in public.
Facts matter...Feelings Can Lie
Since 2015 you can carry anything in 9 or .357 sig made by an approved manufacturer (longish list with the usual suspects on it - glock sig h&k s&w etc). The pistol you choose must be completely stock (except for sights), inspected and approved by a Service armorer and unmodified after said inspection.
That said you can carry whatever you want under the auspices of a concealed carry permit and arguably even LEOSA but the above is what one has to do in order to carry off duty under statutory USSS authority (which is much broader than a concealed carry permit or LEOSA).
Nope.
Frankly the Service is a very liability averse organization. That said, any pistol produced by an approved manufacturer that comes with (usually aftermarket) "go-fast" parts from the factory would be good to go, such as the Sig Legacy models (which iirc had triggers designed by GG?), a VTAC P320, or a LTT Beretta.
Last edited by ChaseN; 08-06-2019 at 01:03 PM.