I can remember that, for a period of time, Colt made lowers with slightly smaller(or larger) pins(and uppers with smaller(or larger) holes as a result?).

Is this something that colt still practices?  When did they stop?  The pins feel to be about the right size based on all the M16's and M4's I was issued.  Without the aid of a micrometer, What is the easiest way to tell what size you have?

(I'm asking because I would like to slap a spikes dedicated .22 on my lower, if they were small(or large) pins, would it be a rattlely inaccurate mess?)

Thanks in advance.

ETA:  I could have my info backwards, and the pins were over, not undersized.  Sorry!

I believe Colt has made oversize fire control group pins and oversize front pivot pins.

I think they were .170 and .315, where normally they would be .154 and .250, respectively.  

I don't recall hearing they ever made undersize pins for anything?


The easiest way to tell is with a pair of calipers.  If your lower does have the oversize pivot pin, you can buy an offset adapter to make it work with a .250 lug upper.