At Trigger Pin Size?

Small pin diameter are generally 0.154 in. in diameter while our large pin triggers are designed to fit AR-15 lowers with a pin diameter of 0.174.

What is the trigger pin size?

The most common pin size is . 154", this is found on most military and civilian rifles. The other size is . 171 which is found in Colt sporting rifles.

What is the difference between large and small pin triggers?

The difference is the diameter of the trigger pins. ALL mil-spec lower receivers that are NOT manufactured by Colt use small pin units. Colt was the only manufacturer to use large pin receivers between the years of 1990-2009.