He has contacted us several times and spoken with everyone of of our staff over the last few months. We have repeatedly asked that he return it to us to see IF there really are any problems or concern. It is VERY hard to fix something when the client will not oblige us by returning it to us.
The question was asked online but not answered as to whether the rifle has even been fired. I see in the for sale posting it is advertised as unfired. Which he has confirmed by phone with one of us, claiming there is no point in shooting the rifle as it would only be wasting ammo, assuming that the few thou of gap will make the rifle inaccurate. AR style rifles by nature have some gap and wiggle between the upper and lower, this is part of the built in tolerances between the upper and lower, yet strangely they seem to shoot well. Unfortunately the client does not want to allow us an opportunity to see IF there really is a problem and correct any problem IF it exists.
It is normal to have a few thousandths of an inch tolerance between an upper and lower. "Zero" tolerance would make it impossible to assemble or disassemble. Seeing a small sliver of light when a hi power light source is put inside the rifle is to be expected. Rifles are NOT water or light proof after all.
Not for an instant are we saying we won't fix what ever is wrong IF indeed there is a problem, but we can't force a person to help themselves.