Does anyone know if there is a "bolt action" type upper/lower receiver for the AR15? I'm looking to built my own AR, and was wondering if anyone makes a receiver like that with the bottom feed mag configuration.

some ideas on the gun are...
.308 cal
24" to 26" barrel
bottom mag feed
manual bolt action
six position telescoping stock

If there is nothing like it around, would it be possible to have one custom made?
...

There are some receivers around (EG White Oak) that have an extended slot instead of a dust cover, with a knob on the side of the bolt carrier.  So you can charge the gun without using the rear handle.   Get one of those, then disble (crimp, epoxy) the gas system, and WALLA!  Straight-pull bolt-action rifle.

The knob on the side seems handy.  I'd like one with a three-way selector - safe, semi, and bolt-action (gas cutoff).  That doesn't seem as easy as a full-time bolt-action.

There are bolt and pump action "AR15s" made for use in countries where semi-auto is not legal.  You might look into finding some of those parts.