  In this letter, we develop a converse bound on the asymptotic load threshold
of coded slotted ALOHA (CSA) schemes with K-multi packet reception capabilities
at the receiver. Density evolution is used to track the average probability of
packet segment loss and an area matching condition is applied to obtain the
converse. For any given CSA rate, the converse normalized to K increases with
K, which is in contrast with the results obtained so far for slotted ALOHA
schemes based on successive interference cancellation. We show how the derived
bound can be approached using spatially-coupled CSA.
