I have put a lot of lead through polygonal barrels in my life, mostly 22 rifles. Some of the best 22's in the world have had polygonal rifling for decades, and have never had a problem. With 22LR or 10MM the polygonal barrel is not a problem with lead and seems to actually do better with lead then standard rifling. I do use a rather hard cast lead bullet in 10 mm, but just because it has been the best for what I want it to do, penetrating.
The owners manual does not say anything about using lead bullets, all it says is no reloads. That is lawyer speak to reduce law suits from idiots who over load their guns.
My new G29 SL feeds and shoots the LSWC/HP bullet with amazing accuracy and never a FF from the gun, same with my old fat G29 when using LSWC/HP bullets.
Sorry about the previous posting, I was trying to write and hold a 15 month old grandson who likes to push the buttons.