AEA 50 cal Harpoon Vs Harpoon Magnum Slug Holders

[2Toes2Many]

I have the AEA Harpoon 50 cal, shorty barrel. I use the Texoma steel slug holders instead of the stock plastic collars.

My question is, do these slug holders also fit the magnum cartridges?

If so, I would like to add the 11" 72 ga magnum barrels/cartridges kit with some shot shells and arrows.
Suggestions would be appreciated...

Steve