c1 carbine with beeman kodiacs

I have a question for the experts here. I have a BeemanC1 carbine I bought 30 years ago. Just put a new breech seal in and it shoots great. Question is I have heard shooting the heavier kodiac type pellets could break the main spring due to increased compression. I like them because of the increased hitting impact on squirrels.How much truth is there about this?
 
I always wanted one of those. I remember seeing them in Beeman's catalog in the 80s. After I bought their .25 Crow Magnum rifle, I was out of air rifle money for years. You don't see them come for sale much I think I may have only seen a half dozen used one for sale on the net in the last 20 years. Congrats on keeping real neat little carbine. I don't remember hearing that. All I ever heard about springers was never fire w/o a pellet.