If your lower is not 'high-mileage', look at root causes first. A non-full-auto rifle shouldn't be experiencing "walk".
Check/replace...
(1) Hammer & trigger springs are strong.
Aftermarket ones (not Colt/BM/Armalite)
may be weak.
(2) Hammer spring legs may not be riding on
pin grooves.
(3) Check disconnector spring for proper
tension, positioning.
(4) Hammer has an internal "J-pin" spring
that 'latches' onto central groove of
hammer pin. Sometimes this is missing.
(5) Hammer/trigger pins' grooves have too
much coating (parkerization, etc.) so
spring legs don't sit deeply enough.
Take a triangular file and deepen the
groove by removing a tad of coating.
I had pin walk problems - Colt lower, Bushmaster "Colt parts kit" and some Colt pins.
Switched one pin set to Armalite pins, and cleaned up one pin set's grooves myself with dental floss & wet Comet, then cleaned & relubed pin w/CLP. No problems since - 500+ rounds later.
Some pins (Armalite, as I recall) have 3 grooves instead of two, and may perform better (i.e., left, center and right grooves instead of just one side and one center groove) since both hammer spring legs can latch on.
If you have a post-89 Colt lower (preban or postban) that went to the larger pin size of 0.170" there is also a wider pin available for the CR6724 "Match" SS bull-barrel rifle. These pins are 0.173" as I recall.
Bill Wiese
San Jose, CA