Lehigh Defense makes an extreme penetrator that is the closest thing to armor piercing. The projectile is solid copper with a special design that increases penetration over standard round nose or flat nose bullets. If you want to see how well these penetrators work, watch this video.
Lehigh Defense Xtreme Penetrator 9 mm Ammo Ballistic Get Test
Another competitor in the inexpensive ($0.20/round) steel cased ammo is Pobjeda Technology out of Bosnia. Their 9mm ammo is steel cased with a copper jacket 115 grain bullet. The primers are non-corrosive and boxer type.
Pobjeda Technology is a munitions manufacturer located in Gorazde, Bosnia. They are ISO 9001 compliant, which is a huge deal. ISO 9001 is a very high quality standard.
Pobjeda Tech 9mm ammo comes in 100 rounds cans and 1000 round cases. The 115 grain bullet is loaded to 1150 fps.
Wolf WPA 9mm ammo is loaded with polymer coated steel cases and FMJ bullets. This ammo is ideal for training, target practice and SHTF type scenarios. The primers are Berdan style and non-corrosive. The steel cases are low carbon annealed steel and will not harm any gun barrel or chamber. The steel cases are coated with a polymer to prevent corrosion, assist in smooth feeding and easy extraction.
WPA ammunition is manufactured in Russia, Ukraine and Serbia in some of the largest ammunition plants in the world. It is not low quality, cheap ammo.
I have shot many rounds of WPA ammo in my Glock and it has been 100% reliable.