If you're getting good accuracy, you might just be forced to swab. I will guess that you are shooting Triple Se7en 2f. You could try a cleaner burning powder like APP, or go to a different projectile. Are you using a witness mark to make sure that perhaps you only think they are short loading?

Some people use one bullet for their first shot and something totally different for the second shot. It seems strange that a Shockwave is giving you that much trouble, but things like this happen. It could be the rifle, but I suspect it is the powder really....