Hello Mike,
I used a few of the original Benjamin pellets when I first bought the gun to give it a better chance of functioning reliably. I then compared the profile of these with more readily available brands and settled on Milbro Caledonian and Marksman No2 as being the closest. Both feed well in my 422 with just the very occasional multi pellet discharge.
I fitted a small square of Velcro below the breech to prevent the magazine follower marking the end plate as it has quite a strong spring.
Brian