From the website I found something I've never heard of before... It's hardcast bullets with polymer coating... Here's what DoubleTap has to say....

220gr. Hardcast Heavy Hitter!

For the avid hunter or plinker that wants to shoot hardcast through their 10mm, here is your chance! This is the only factory 220gr load for a 10mm currently being produced. At 150yds this 220gr slug is still traveling over 950fps! This is equivilant to a .45ACP +p at the muzzle! These slugs are cast to 16 BHN and coated with a polymer coating to prevent leading even out of polygonal-rifled barrels.

Caliber : 10mm

Bullet : 220gr. FP Cast

Ballistics : 1125fps/ 618 ft./lbs. - Glock 20

Anyone have any experience with these bullets? Do they foul your barrel with polymer?