1...That's plenty of pellets...

2...Excuse my ignorance, but isn't that a 3 1/2 mag???
If so...try 3 inch shells...I have seen it make a difference...
I have a buddy that has the same gun (if its a 3 1/2) and he
finally went to 3 inch Federal Premiums #5s and the Remington
x-Full choke...