Purchase upper receiver and vise block from Eisenach Arms and insert upper into vise block.
Insert retaining pins and cotter safety pins through take-down holes on receiver.
Place vise block and receiver into vise securely.
Insert barrel with pin up into pin slot on receiver.
As shown
Barrel in place.
Apply all purpose oil or grease to upper receiver threads.
Slip barrel nut on barrel. (barrel nuts vary in design)
Hand tighten barrel nut.
After being screwed on by hand or light wrench pressure, we see the gas hole is NOT in line with barrel nut gap!
Purchase AR armorer tool from Eisenach Arms and apply 30-40 ft.lbs until gas hole is in line with gap on barrel nut. If in between holes, loosen and tighten nut repeatably (3-4 times) until desired alignment is achieved within the specified torque range. Do not over tighten to obtain alignment.
Properly aligned barrel nut shown.
After retaining gas tube into gas block with roll punch, insert gas tube into gas hole on the upper receiver.
Gas block will butt up against barrel stop. Index the gas block on the barrel to align the gas ports. Tighten set screws or clamp screws. (Models Vary) 
Install free float hand guard. (Models will vary)
As shown
Tighten the hand guard bolts.
Do NOT over do it!
Slide on shim (if needed) and crush washer (dish towards muzzle)
Secure with AR armorer tool until flash hider is in correct alignment. (Models Vary) and.......
 Time to go shoot your NEW Eisenach Arms Side-Charge Upper!!!