What is the diameter of the crossman nightstalkers barrel

not at all. the Benjamin has a pump handle like the rack of a shot gun below the barrel. the Crossman 3100 the barrel is what you **** the round in with. the Benjamin shoots pellets and bb's the Crosman only shoots bb's

Time to buy a new model. I had 2 of those with similar problems and couldn't find parts. Try the CO2 model 1088. I'm happy with mine. Spray the seals with silicone spray monthly or every 2 cartridges.

I had this same problem. You need to either rebuild or replace the valve assy. it is not hard to do and the parts are available from crossman for about $14 I think that the valve assy costs about $24 the parts list is on crossmans web page

i put a little piece of wire under the clip,which holds it up.

The piston doesnt lock on the trigger. if trigger is adjustable set adjustment more coarse. Check also sure that trigger mechanism is in forward position and not stuck halfway. If still not hooking see if piston hooh and trigger catch not damaged. very seldom the piston will twist inside making it impossible to hook, just realign piston.

Do u still have the gun I've got 1 if u still need information

Check thare is a rubber o ring missing or broken in the air chamber

The barrel pushes the piston back when you **** it.

The seer grabs the piston to hold it.

It sounds like you have an engagement issue between your seer and piston.

Often there are springs which hold the triger paul and seers in place. You may have lost a spring which isnt allowing your trigger mechanism to reset after the trigger is pulled. This results in the trigger being permanitly in the fired position.

Good luck and hope this gives you something to look for

Try with this:
http://www.network54.com/Forum/275684/message/1136858902/nightstalker+research+pics+%28long%29

Regards.

ACA.

try tighnening the screw or bolt that holds the pump on the gun