In various embodiments, a surgical stapling head is provided that may comprisea staplecartridge for supporting one or more staples, a core movable relative to thestaple cartridge, atleast one staple driver extending from the core, and a casing configured to atleast partially holdthe staple cartridge and movably receive the core and the staple driver(s).The casing mayfurther comprise at least one retention member that is configured to move froma first position toa second position when sufficient external force is applied to the retentionmember, such as thatprovided by a shaft of a surgical stapler during insertion of the staplinghead assembly into theshaft. When the retention member(s) are at the second position, the stapledriver(s) may beprevented from driving staples from the staple cartridge, thereby providing afiring lockoutfeature to the stapling head assembly during insertion into at least a portionof a surgical stapler.
