Benjamin Question about pumpers and springers

I have some of those both in the can and in the little yellow plastic box. I have only tried them in one other .20, an HW95. Rather poor accuracy resulted. I think that they are too heavy for that power plant in a springer, but that's a guess.
They only weigh a little over 13 gr so I don't think weight is the problem. I would think that since there are little to no skirts, engaging the rifling would cause them to not be stable and cause them to be inaccurate.