Polygonal rifling is no different when it comes to leading.
You either have it right or you don’t. If you have standard rifling and you get leading you can increase pressures and blow your gun up.
IRRC the issue is that polygonal rifling take a slightly different approach with bullet to barrel fit which is not something you can control in factory or commercially reloaded ammo.
If you roll your own you can figure the right size and order or make what works for your gun.
This is no different than any other gun with cast.
Cast gets a bad name because commercial/reloaded bullets are made undersized, too hard or too soft an alloy.
Check castboolits forum for plenty of guys that shoot thousands upon thousands through their Glocks with no need to clean.
That being said you can try a handful of shots. Check the bore. Try a handful more. Check the bore. That way you can determine if there is any issue with the ammo before builds significant pressure issues.
It doesn’t take many rounds to tell if it’s going to lead or not.
With a bullet .001” undersized in my 1911 I could barely see the rifling under all the lead after 2 mags.
Step it up .001” And I literally fire thousands of rounds with a shiny bore when I’m done.
In short, be safe. Don’t trust anything you read on the internet (including this) and proceed with caution.
Edited to add: this is a picture of Metford rifling from somewhere around the late 1800s when there were no copper jacketed bullets. Only some with paper jackets. These rifles are shot still today with bare lead.
