Inerta driven, low power shells provide insuficient inertia to cycle the gun. That being said my SBE II cycles 7/8 high velocity remingtons from walmart. If it really bothers you can buy a lower power spring in the recoil piston tube in the stock, but you will need to switch back for higher power loads or risk damage to the action. My recomendation is to load the gun with higher dram loads in 1 and 2, then put the low power load in 3. This way the jam won't cause any problems.