I am strongly considering buying a Chip McCormick drop in trigger for my Colt.  However, I am not sure if all Colts require the large pin size or the small pin size and I don't want to order the wrong one.  I have a Colt Match Target HBAR manufactured in 1998.  The best I can tell, it is not a large hole upper and receiver.  I was told to use a caliper to measure the pin size but unfortunately I do not have access to one.  Can someone help me out and tell me which pin size is correct or should I just wait until I get a caliper and measure it?

All Colt "Match Target" series (aka post-ban) are large trigger/hammer pins. They haven't made a civilian-market mil-spec trigger/hammer pin lower since the "Green Label" days circa 1989.

Mark