The Schmeisser S60 was built specifically for .223REM or 5.56X45MM ammo only. Schmeisser & American Tactical have done some testing and found that the S60 may not operate with all types of .300 Blackout ammo. Due to inconsistancies with different brands, Schmeisser does not recommend using 300 Blackout with this magazine. Failure for the magazine to operate with 300 Blackout is not covered by American Tactical's Limited LIfetime Warranty.
Warning! - High Tension Spring
The Schmeisser S60 has a very powerful high tension spring. Please use caution if disassembling the magazine for maintenence. If not properly secured, spring may eject from magazine when floor plate is removed and can cause serious injury.