All the GP-100's that I've seen are DA/SA, I didn't even know that they made a DAO model. More than likely the only thing that even makes that one DAO is the lack of a hammer spur, I would imagine the lockwork is the same. Probably if you replaced the hammer with one with a spur it would function DA/SA again.
I looked at CDNN's catalog and lo and behold, they're selling them for $250 dealer cost. Apparently they were for an overseas contract. I E-mailed the seller on gunsamerica and he said it could be converted back with the instalation of a new hammer. But I'm not too fond of the extra rounded grips, and I don't know where I'd find a hammer.
My dealer quoted me $360 on a blued, $395 on a stainless GP-100.
Also quoted $325 on a Stainless Taurus 65. Decisions, decisions.
Trust is earned, not... GIVEN away. - Worf
I went revolver shopping and I didn't like the Taurus action. I'm a Ruger nut, but I thought the S&W had the crispest trigger. I ended up with a S&W revolver in 10mm. It had the best action and was in the best caliber.
Now I have to figure out what to do with my Security Six.
"The secret to life is honesty and fair dealing, if you can fake that you've got it made"
I have a Ruger Police Service-Six -- predecessor to the GP-100 -- that is a true DAO: there is no full cock detent for the hammer. My gun was made as part of a 1988 contract for NYPD and was virtually new, maybe never even issued as I believe the NYPD went to 9mm autos. The hammer lacks a spur but clearly has the advantage of not catching on clothing. I believe the action was worked to a smoother degree than the civilian Security-Sixes as it is darn near as accurate as my Glock model 17. I would bet dollars to doughnuts the police GP-100's are very similar.