Do you belive that a duty size carry gun can make a good ccw if you can conceal well and manage the weight?
Short answer: Yes. I have done it.
Longer answer, as follows:
1984 to 1985: I experimented with carrying my 4” S&W Model 629 during personal time, but mostly carried a 2.5” S&W Model 66.
1985: HK P7, on and off the clock. Is a P7 a “duty size” gun? Yes, of course it is. Very flat, but yes, a duty pistol. A local leather smith made a PD-spec flap holster for me.
1985 to 1990: S&W Model 58, .41 Magnum, on duty, and during much personal time. That is a 4” N-Frame. Big Bore times!
1990 to 1991: Colt Stainless Combat Commander, on and off the clock. (Reliable when new, then became finicky, so, sold off.)
1991 to 1993: SIG P220, on and off the clock. Reliable pistol, but, the heel-clip mag release occasionally snagged patrol car seat back fabric, causing a partial mag drop.
1993 to 1997: Ruger 4” GP100, soon joined by 4” K-Frame Models 19 and 66, on and off the clock. Yes, back to revolvers; tired of problematic 1911 and SIG.
1997 to 2002: Full-sized 1911 Colt Government Model and Kimber, on and off the clock. (Wonderful, until a compatibility problem with the then-mandated duty holster was discovered, at which time I reluctantly transitioned to Glock.)
From 2002 to some time in the 2006 to 2008 time frame, I finally broke my pattern of carrying the same handguns on and off the clock. While I carried full-sized Glocks at work, from 2002 to 2004, and then transitioned to the SIG P229R in 2004, I normally carried 2.25” and 3” SP101 revolvers, during personal time, occasionally up-gunning to my 4” GP100 or 4” Speed Six.
~2006/~2008 to 2012: Non-railed P229 during personal time, while I was carrying a railed P229R while on duty.
2012 to 2015: I phased my favorite 1911, my Les Baer Thunder Ranch Special, back into being my personal-time pistol, while I kept carrying my P229R while on duty.
Why? An all-steel, full-sized 1911, firing the slower-accelerating .45 ACP, vexed my arthritic right hand much less than .40 fired from a high-bore-axis P229.
2015 to 2018: Glock Gen4 G17 while on duty, and during much personal time, starting soon after my then-chief again allowed 9mm to be a duty cartridge.
2015 to 2018: Full-sized 1911. I did not put my Les Baer pistol away, when I started carrying Glocks.
2018 to present: I retired from LEO-ing in 2018. Such physical limitations as aging right wrist and right shoulder joints make it more difficult to draw a full-duty-length handgun from a typical concealment holster. So, while can still conceal a duty handgun, in a typical concealment holster, a shorter-barreled weapon “clears leather” with less wrist and shoulder articulation. My single most-often-toted Handgun, an S&W Model 64, is on a duty-sized frame, but has a 2” barrel. when I go out at night, I may well select my 3” GP100, which has a glowing tritium front sight. I have lefty holsters, so sometimes add a big gun as the second gun.
Edited to add: From 1993, onward, I have never completely stopped carrying my favorite 4” GP100, at least some of the time. There have always been occasions when I just simply felt like carrying it, either as “primary,” or toted in an alternate position, as a second weapon.