How do the new AT receiver differ from the old AW receiver? Externally at a distance they seem pretty much the same, but how do they differ? Are there any interior differences. For example the AW has an internal removable locking ring which can be replaced to adjust headspace in older rifles - do the AT have the same removable locking ring? And any close up pictures of the new barrel locking system? Both pictures of the exterior and interior of the receiver's barrel mounting system would be appriciated