Decided I'd swing back around and do a quick n dirty write up on the rebuild process since I couldn’t find it anywhere else... this is from memory last week, and may not be 100% accurate, but is pretty close and better than no guide at all.
The $40 rebuild kit came with a new gas valve, bolt o-ring, pump arm pivot pin, gas piston seal, and some oil.
- remove stock from receiver via the big phillips head screw on bottom of stock
- remove trigger assembly via one phillips head screw on either side of the receiver, set the trigger assembly and receiver spring guts to the side
- remove the two small phillips on the side of the receiver that hold on the bolt cover, exposing the bolt retaining nut
- remove the bolt retaining nut and slide the bolt out the back of the receiver
- remove the large threaded nut that the stock was retained by, this releases the gas valve
- pump the rifle a couple times and the gas valve will start working out, you’ll probably need some long needle nose pliers to get it out all the way
- drift out the two roll pins at the front of the barrel to release the gas tube cap and pump handle and lever
- pull the gas piston out to the point the retainer pin lines up with a hole in the gas tube, drop the pin out, now the pump lever and piston are released, slide the gas piston out the end of the gas tube
- clean any debris or old oil out of the gas chamber, a cleaning rod and 12-gauge brush with patches on it worked perfect
- replace the seal on the end of the gas piston and re-assemble the pump arm and drift back in the roll pins (don’t forget to get the end cap and pump levers lined up correctly)
- lube up and slide the new gas valve in place making sure you keep the threaded portion aligned perfectly down
- lock the gas valve in place with the large nut from the underside
- replace the o-ring on the bolt stem, insert back into the receiver, lock in place with retaining bolt, reassemble the retaining/cover plate
- put the bolt spring guts back in place, slide the trigger assembly back on to the receiver and lock in place with the two screws opposite each other on the receiver
- place the rifle assembly back into the stock and secure with the large phillips head
That’s all there is to it, the hardest part is drifting out the roll pins, and those can be REALLY stuck in place.
Mine shoots fine again but I still don’t trust it to last for good, I’ll be getting an RWS 34 or RWS 350 magnum soon as I can confirm they’re quiet enough for back yard plinking. Worst case scenario if the RWS is too loud I’ll pick up a Gamo Whisper with nitro piston, which should be considerably more powerful, accurate, reliable and quiet than the Benjamin 392 – just doesn’t look old timey with a wood stock which was a big draw for the Benjamin 392.
