Rats may need a heavier shot, thinking 4-6 weight...birds your 8 shot may do.
Do you have any tear down photos of the barrel ? I'm looking to get a spare made or purchased, and the engineers that designed the vortex have declined to answer my email requests for a parts diagram.
Those look like generic gel capsules so maybe 8 shot?
Looks promising wonder how much energy it Carrie's.