I have a postban Colt LW and to me it seams to have slop between the receiver and the lower,is this the way its setup from colt??? I'm not a gunsmith but i am a mechanic and the tolerance doesnt seam right. There seams to be enought that i would think that every shot would diffrent. Do i just have to much time on my hands or is thia a common problem with all AR's

So everyones AR is tight then? I guess my colt is the only turd in the bunch.What i mean is if i place the lower in a vice and clamp it I can rock the upper back and forth.I guess i should contact Colt.

Nearly all ARs have a bit of movement between the upper and lower; and if they don't when new, they develop a bit over the years, from being opened and closed a few hundred times[:D]

No, it doesn't effect accuracy, because no matter where the upper is in relation to the lower, the barrel to sights relationship doesn't change. It is a bit of an aggravation though, and that's why there are two or three different items on the market that will fix the problem, either by putting a rubber wedge under the rear attachment point or, more expensively, byusing a screw adjustable type rear push pin to wedge the upper down on the lower. Either will give you a more solid feel. Niether will improve your accuracy.[:D]

thanks Sham.

Brian:
If the looseness bothers you try an "Accu-wedge."  They sell for a couple of bucks and are effective in eliminating play.  shamayim is right though, in that the play has no effect on accuracy.HTH

get an accu-wedge.  It will make you feel better, and it could improve practical accuracy, because movement of your grip hand and body will be more accurately transferred to the upper. (tighter grip, sturdier platform).

Brian,
The other choice between Accu-Wedge is the AR tensioning pin, which you can get from Bushmaster or JP Enterprises. This little gem is MUCH costlier than the Accu-Wedge, at around $30, but it will take ALL movement out of the upper to lower.
As stated earlier, really won't improve accuracy in and of itself, what these two items do is help prevent movement while you are getting your sight picture, stopping any unwanted deviation when you s-q-u-e-e-z-e the trigger.