When I first started CCing, I longed, I pined, I ached for a shoulder holster; after all, the CDI factor is off the charts.
After doing some research, I settled on the Fobos shoulder rig with Roto-holster attachments which allowed me to switch-out holster bodies quickly if I decided to carry a different gun.
It works. It's comfortable. And I never, ever use it.
Reason being, the only time you can wear it without OCing, is when you wear a jacket and never take it off. Which looks really bizarre when you walk into someplace out of the cold and it's really warm and you have to just stand there and sweat (as I was).
And if you open carry with a shoulder rig, and are not currently sworn in as some sort of peace officer (and even then it's borderline) prepare yourself to be considered a douchebag (as I was). It's just too over-the-top. I rate it a 9.0 on the DB scale and I only rate open-carry-in-a-drop-leg-holster a 7.8
If you're hell-bent on it (as I was) I suggest you go one of two routes. Either get a custom leather job fitted to you so it's so comfortable and so expensive that you absolutely have to wear it or you'll become ill, or get a cheap one so you don't feel quite so bad when you quit wearing it.
My $.02
-'bridge
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