I doubt that the ammo is the issue...
Make sure the gas cylinder plug is tight. A loose gas cylinder can cause a loss of pressure. If you have a poppet-type gas plug, make sure that there is no crud in the valve, which may cause a leak.
A worn gas piston on the op rod can also cause function issues as well. Minimum piston diameter should be diameter of .5250"
Another issue, albeit less common, may be the alignment of the gas port in the gas cylinder.
Also check the operating rod spring to make sure that it's not worn/damaged.