Given the extremely high temperatures across the country, it's probably a good time for us all to remember about valve lock on C02 air rifles and the benefits of shooting in a nice, cool basement right now.
The QB78 family - like all other C02-powered air rifles - will suffer from valve lock when the gun reaches a temperature in the region of 90 - 95 degrees F.
Valve lock occurs due to the increased pressure of CO2 in the air rifle due to the effect of temperature. This increased pressure overcomes the strength of the valve spring and prevents the valve from opening fully. The result is a significant drop in muzzle velocity.
The good news is that this is a temporary phenomenon and that the gun will return to normal when its temperature drops.
So, keep your QB78 - or any CO2-powered air rifle - in the shade whenever possible when shooting. Better still, shoot in a nice, cool basement range where the temperature is a lot lower: both you and the air rifle will be a lot happier
Archer Airguns Inc.
Online stores http://www.archerairguns.com
I think you mean hammer spring as opposed to valve spring..... The valve spring keeps the valve on its seat, the hammer springs is trying to dislodge it when you pull the trigger.....