After some struggles finding an appropriate stock for the rifle, the J180 is put together!
First impressions are...ok. The weakest part of the platform is the fit and finish. It is not anodized I think, it is a matte grey color and feels like parkerization but I don't think you can parkerize aluminum. There are machining marks in many places, and the trigger pack is assembled from 2 halves and bolted together. There was an abundance of packing oil on and inside the receiver, but it all wiped off easily.
The bolt cam pin track was marred out of the box. Looks like cycling and dryfiring the receiver might have caused the cam pin to strike the track, the marks are on spots the pin might not have reached if the BCG had been in the correct position in the receiver when stopped by the barrel extension.
Trigger is pretty decent out of the box, single stage trigger pull is on the light side with a short audible and tactile reset. It has a quirk where the trigger seems to lock up if the safety is set to "on" after the hammer is dropped but before resetting it. Only way to remediate is to remove the trigger pack off the gun and reset the hammer manually with the safety off.
Since the recoil rods and spring are higher on the receiver, the height of the receiver is higher than the height a standard AR receiver; this causes the receiver rail to be around 3-4 mm higher than a standard AR handguard rail I would guess. This in turn causes a very pronounced issue with AR-height optics, necessitating a higher comb on the stock to properly look through optics. Using a Magpul MOE stock and 0.5" cheek riser the AimPoint PRO can be used normally.
Last but not least is the issue of stock options. As I've previously indicated, A1/A2 stocks will not work on this receiver set. However, I found the Magpul fixed carbine stock will work as it interfaces with the geometry of a carbine buffer tube to prevent rotation.
Range report soon!