Barrel Probe O’ring Change on Mutant.

When I started getting spurts of air on the cheek after each shot I took I knew my barrel probe oring was either damaged or no longer in the groove that is cut behind the brass grommet that accommodates the pellet probe. With the help of some folks on the board I did this fix and found it to be very easy. There is no need to remove the action from the stock however I would remove the scope or at least rap it up and protect. You should probably do this every time you work on your gun to protect your glass. For .22 calibers the oring size is (5.28 X 1.78) for .177 the oring size is (4.47 x 1.78).

First loosened the four screws on each barrel bands these clamp the barrel and air tube down. After these are loosened, take out the grub nut that locks the barrel down into the receiver (you will find this grub screw on top of the receiver above the brass grommet). Now carefully slid out the barrel to access the back of the brass grommet inside the receiver. If you look at your barrel there is a impression drilled into it this is what lines up the barrel correctly so the air transfer port is correctly positioned make sure when you slide the barrel back into the receiver this indent lines up with the grub screw hole. I found the easiest way to get the oring seated in the back of the brass grommet is to lube the oring with some Silicon grease and center it to the bore on the barrel. The grease should hold the oring onto the barrel like glue, after it is centered gently push the barrel all the away into the receiver and pull it back out slowly to see if oring is seated correctly in the grove on the brass grommet. You can look in to the receiver and see if it is seated. Now push the barrel back in to the receiver and line up the grub screw hole with the indent on the barrel tighten the grub screw down. Then tighten the barrel bands. Top screw on one side lower screw on the other side of each band in a crisscross fashion.

Hope this helped.