I have the same gun. I love it. The only problems I've had is gunk building up under the ejector star. I used too much oil. The oil collected the gunk. I use Hoppes #9. Cleans it up nice. Here's a Hickok45 video on Revolver cleaning. He knows more than I do...
The previous owner may have filed down the strain screw and replaced the springs. Not an uncommon modification. Some think they improve the trigger by lightening it.
MidwayUSA and others will sell you a new strain screw and spring kit to bring your S&W up to "spec". Cost is small and its an...
I guess that's what happened. It did have a nice trigger. Too bad it only fired about half my rounds loaded with CCI primers. He may have tried to "tune" his revolver to the ammo required by his department. I've had no problems since I replaced the strain screw. Great gun.
I have a 10-11 heavy barrel also from Victoria Police. Beat up, but shoots good. I replaced the filed down strain screw and the Uncle Mikes grips. After that I just shoot it and clean it and shoot it again.
M10's are great guns. I hope you enjoy yours as much as I do.
Open the cylinder and look on the frame, just under the barrel. You should see the serial number and 686-6 just below. I have one from 2013. They're great guns, enjoy it.
Could you be a little more specific describing your defect? I don't see much difference between your gun and my stock 686. Your hand seems a little longer, but maybe its the light or camera angle. Good luck with your new 686. I hope you get it sorted out without a return to SW.
Bernhard Goetz, NYC subway shooter, back in '80's used the 38 caliber Model 38 Airweight to shoot 4 attackers. He served 8 months in prison for carrying an unlicensed firearm. He also had legal fees and lawsuits to deal with.
Use of a gun is the last resort.
Are you sure its a -8? The last I heard SW was still making -6.
I'd poke around the S&W web page for parts. They may have what you need on hand. If that fails, keep checking Midway.
Good luck with the 686 :)