I own a xm177e2 and a colt model 655 philippine version carbine with a 14.5 (total lenght), both came with retractable stock, and both are selective fire..pure orignal...my problem is sighting it in for say... 25 yards... I read an article by chuck taylor way back in 1992 that the xm177e2 and maybe the 14.5 inch barrel is very hard or sometimes impossible to zero...is this true?? i havent fired alot in both of them to know for sure...I am wondering if chucky is telling the truth or not...he said that the shrt barrel AR ...say..14.5 inch and below are near impossible to zero accurately....any body ever zeroed his/her shorty?? how??

You can zero short barreled rifles/carbines the same way you do a full size rifle. The big difference is velocity, something a shorter barrel has less off. So at at distances beyond 100 meters you POA/POI will differ with that on a 20" barreled AR. Since the lower velocity allows drag and gravity to influence the bullet more.

I have a M4clone w/ a 14.5 inch barrel and zeroed it without any problems whatsoever, same goes for my brother's 10" Bushmaster carbine.