Walther LGR Problems...help?

[Cola]

Hello I recently joined this forum and purchased and just received a used Walther LGR side lever 10 meter rifle from a trusted seller whom I have had good dealings with before and I have 2 of these and the one I just received has a problem holding air as you close the pump handle air hisses out of the barrel I shot it about 10 times and it worked fine but seemed a bit slow velocity wise then it does not hold air any more. My other LGR breech pops open when I fire it. I have to hold the breech down when I fire it then it shoots fine otherwise it shoots like a scattergun when the breech pops open upon firing it.
HELP?
TIA

Cola

[mnsty]

Sounds like a leaky valve and a barrel adjustment is needed.

[samg]

If you scroll down AmBraCol posted a good procedure for resealing a LGR. It may help diagnose your problem.