View Full Version : AR fitment issues..

05-18-2011, 4:59 PM
My FIL gave me one of his ARs to tinker with/fix. He did a cheap build (he has two other good builds), and the upper doesnt fall right into the lower, it has to be forced a bit. it seems as if the lug on the upper is wider than the frame of the lower, or something.
the lower is made by TKS engineering, i couldnt find much on them online.
he also said that it jams every three rounds or so.
the rear pin goes all the way thru the lower frame without the upper in place, but will only go thru the upper when its down. will not go thru the far side of the lower. if that makes sense.

any ideas? im gonna get out the caliper when i have time and measure some things, maybe a file will help. thanks.

05-18-2011, 5:03 PM
One of the halves is out of spec. The way to find out is to try another upper.

05-18-2011, 5:06 PM
do this as well with the 2 parts together put it against a light and take a picture. theres 2 things this can help see if there is a gap in the 2 halves or see if one side is higher then the other.

05-18-2011, 5:27 PM
i will try both. his other two ar's (s/w m/p parts) fall right together, this one gets hung up and has to be forced the last 1/8" or so, and even then the pin doesnt even go all the way thru. would this cause jamming issues though?

05-18-2011, 5:34 PM
No mention what make. or the lower is 80%. maybe not machined properly