tight fitting AR upper and lower

GreenLantern

I got two ARs. Both the same brand and I swapped the uppers and lowers, but with one, the fit is really tight. The rear take down pin is pretty tight. When taking it apart I usually have to get it started with something other than just finger pressure. Also, the forward pin is REAL tight! Can't pull it out by hand till it's about half way started with a screwdriver or something. What can I do? Get some new pins and file them down some to get them to fit better? Keeping the old ones for if and when I swap parts back. My only concern with it the way they are is if it's possible that the lug (for lack of a proper term) on the back of the upper might break off under stress cause it's aluminum and therefore softer than the lower receiver. Any ideas would be great!GL

cpermd

The smartest move is to put two or three pins that fit in the grip or butt.You can put them in a drill press or your wife's egg thingy with 320 sandpaper til they are snug for each.Don't touch the lowers unless there is an obvious mismatch with all the uppers you can lay your hands on.Only file an upper with the tightest lower it will sit on.USE the pins every time you can.cpermd

v35

The AR upper and lower are both aluminum. How about just using some super lube on the tight pins and the holes in upper and lower and doing a bunch of shooting.Most owners would prefer to have a tighter rather than a too loose upper to lower fit. In fact there are widgets sold to tighten up the fit.If you take a pin out and file it, the surface roughness on the filed pin will enlarge the hole in the soft aluminum upper and/or lower and you'll really be up a tree. If someone could polish the pin down on a lathe, removing about .001" (one thousandth of an inch) and leave you a bright finish,it might solve your problem.