In guns like the Glock and Kahr, that have polygonal barrels that advise against lead bullets, are copper plated lead bullets ok? I load 124 grain 9MM RN bullets from Xtreme Bullets.

yes i use them all the time in my glocks. i also shoot lead in my glocks, just clean it good after shooting. i shot lead in one of the first glock 17s that came out before anyone said you should not. the problem was the lead deposits not being removed before firing a factory high pressure jacket round.

With the Xtreme 124gr RN plated, out of a 3" Kahr PM9 pistol......

w231 at 4.2 grs with a OAL of 1.14" did 913fps and shot at POA.

You can get up to 1112fps with Unique powder with 1.14", if needed.
A short 1.12" OAL did not do well in accuracy in this pistol, with this bullet.

This 124gr plated did even better in my C9 3.5" with a longer 1.165" OAL
where there were no feeding problems from 916 to 1200fps.

Plated works just fine. I'd be cautious with some of the "eco" or cheap plated, but a thick plating like Xtreme works just fine.

Plated work just fine. Another option, which works just as well, and is cheaper too are the Hi-tek or polymer coated bullets. These can be found from Blue bullet, bayou bullets, acme bullet company, sns casting among others. I prefer to shoot these from my pistols over the plated, and haven't ran into any issues. Just make sure you have a proper bell on the case to eliminate any shaving of the coating.

I've really gotta price out the coated for 9mm. Trying them out wouldn't even be a huge deal, I've got enough non-polygonal 9mm barrels to run them through if they don't work.

No problem. I have run them thru Glock and H&K, extreme, rainier, berrys. all have given me no problems.

Wise A, prior to trying the coated bullets, I mainly shot JHP, because I liked the accuracy they gave. My first time trying the coated bullets from bayou, I was impressed by not only the accuracy / consistency, but also how clean they were. The coatings are really tough, and will stay on the bullet even after shooting steel. It's pretty impressive stuff. While I've only purchased from bayou and blue bullet, any of the company's I listed will take care of you.

The only synthetic jacketed bullets I've shot so far is the Federal American Eagle total synthetic jacketed ammo. The bore stays far cleaner than with lead or copper jacketed or any other I've fired. For some reason they label it "range ammo", must be it's not good to shoot bad guys with if you ever have a need to neutralize one.

__________________
Certified NRA rifle instructor

Shoot lead and everything else out of my Glocks, I just clean the barrels when I'm done. Simple really.