[Scattergun Bob]

M1 S90 shotguns are race horses, and do require a bit of maintenance.

First off, I have a few questions;

what vintage is you S90, is it a HK model or post HK?
is the cocking handle round or curved?
Have you removed the trigger assembly?
Do you know if you have the light or heavy action spring?

Most of the time this failure to feed is caused by light loads, or a dirty lifter spring. However the above questions will help me understand your scattergun more better!

I carried the Benelli entry model for a number of years, and have an early HK/Benelli M1 S90, both are picky about dirt and grime.

A bit of thought from the armorers from HK concerning the M1 S90

It's not a pump, it's a self-loader simply means that we must condition our minds to except the fact that the gun uses mechanical energy "other than our arms" to operate. This is a fact, and it denies us the ability to jam the bolt open or closed by sheer force of " will and arm".

Remember, in the middle of the gunfight, no matter how strong your ARMS are, forcefully racking the fore-end will not make up for poor PMS (Periodic Maintenance Service) of this weapon and that's guaranteed!

Good Luck & Stay Safe