Make sure the elevation knob has complete, and consistent, engagement 360 degrees of rotation.
My nephew had an Armscorp receiver which was way off in that feature. The receiver was purchased as a new, un-built, receiver on commercial row at Camp Perry in mid-90’s. Flaw was not noticed until the receiver was built into a full rifle. Jack refused to make the matter right.
The Asian gal went to work for Fulton Armory on commercial row at Camp Perry after Jack’s death. I bought a set of Israeli FAL handguards from her at a hole in the wall gun show at a small VFW hall in Virginia. Cheerless personality. She does seem to know her ware’s.
That is ANOTHER problem with the infamous Armscoro "machining". The area for the rear sight assembly MAY NOT be machined "square", making it (nearly) impossible to properly install a rear sight assembly WITHOUT getting this area properly machined. ANOTHER freebee from the incorrect machining is UNEQUAL LENGTH of the legs that hold the trigger housing and seat into the stock. These ALSO have to be properly machined to be able to assemble the receiver into a safe, functioning, reliable and hopefully "accurate" M-14 clone. There are more problems but I digress for fear of causing more stress among my M-14 Cult brethren.
When I stumbled into the lust for M-14 clones back in the '70's, I had the heaven-sent fortune of knowing a Master Machinist who also was a Master Gunsmith. Without him, my M-14 clones would be in someone else's possession, most likely as paper weights or with the firing pin and extractors removed, the front ends painted orange and letting the kids play with them. Or, maybe as lamp stands.
Getting the early M-14 receivers made into safe, reliable, functioning and accurate rifles required experience, talent, tools, abundant spare parts and patience on the gunsmith's part and money, patience, energy, money, time and money on the future M-14 clone owner's part. This was before our grander times of LRB , SMITH ENTERPRISES, FULTON and GWLA (spelling?) receivers. I've read BULA and the guys from Cleveland ( 7.62 ARMS?) that were pre-BULA (that later moved to Florida??) had receivers that gave the assemblers headaches. Then there was the danger of getting into trouble with the gummit with the USGI receivers that were cut in half and then later welded back together. Even now, if you have a quality receiver, you still need expertise in hand-fitting and spare parts to get ALL the rifle to function correctly as a whole.
There are plenty reasons why the AR-10 Coven has a vast following that emerged at record rate, especially when compared to the M-14 Cult. I tell yall, I've paid my dues mistakenly falling in love with the M-14. I give up on FALs, and now, these AR-10's are pushing their luck. I'm ready to sell them all, like Gun Plumber did, and just get a SCAR-17S. To me, that is one of the smartest moves I have read on FALFILES.
Jarhead