Just started building my Jard J180 receiver and found a few issues already.
There is no way to install an A1/A2 stock on this receiver, as the geometry of the receiver differs from an AR-15's lower. The dimple the stock would fit into on an AR lower to prevent rotation does not exist in the J180 receiver or trigger pack.
This will also impede instalation of sling loop plates commonly used with carbine buffer tubes. It seems the only stock options that will work with the J180 are collapsible stocks.
The barrel nut instalation is also difficult. Geissele reaction rods do not fit into the receiver as the stock tube channel is lower on the receiver than on the AR-15. There is about 1 cm difference between the center of the stock axis and the barrel axis. Magpul BEV block does not fit into the receiver, so the barrel extension locking lugs cannot be engaged from the inside of the receiver.
My first attempt to tighten the barrel nut of a BCM MCMR handguard involved clamping the barrel on a vice with wood blocks to prevent marring the finish. I was unable to tighten the nut using my torque wrench to BCM spec of 40 ft/lb without the barrel slipping in the wood blocks. The only way I managed to secure the upper was using some thick fabric wrapped around the upper itself to prevent marring, and then clamping the upper lightly near the barrel using the vice. I was then able to tighten the barrel nut to 40 ft/lb.
