The buffer upgrade pertains to the cocking handle. When you let it slide forward the shaft of the cocking handle makes contact with the receiver. Over time this part may snap off. I ended up doing the poor man's upgrade consisting of an 11/16" O.D. flat faucet washer inside the front of the cocking tube assembly. No disassembly of the gun required as you lock the cocking handle, slide the rubber washer in sideways then orient vertically. Release the handle to push the washer forward (repeat). I used a flat head screw driver and slight taps from a mallet to fully seat the washer and I was done. Cost was $2 for a set of 10 of those washers at Lowe's. This should give the handle about 2mm of buffer from hitting the receiver.