shooting the rifle a couple of times with the bolt open(no pellet).Otherwise,use a pick and pull it out.Be wicked carful not to scratch the groove that holds it,if your pick is steel.
Silicon lube a new o-ring and set it within easy reach.
Feed a dowel down the barrel,stopping just before the o-ring groove.use painters masking tape to hold it at the
With the safety on;pull the bolt all the way back till it locks.
Hold the rifle vertically with the muzzle down.
Obtain o-ring,and squeeze it till it looks like a figure of 8.
Stuff one half of the 8 across the breech opening,and into the groove made for it.
use your index finger tip to squash the other half of the 8 into the groove.It will open into an O shape on its own and fill the groove.
This took me 3 tries before I got it right.