FWB 600 - Affected by temperature?

[philip_T]

I was benchresting my rifle today at 25 yards for pellet testing. I had a small ceramic heater about two feet to the right of the action to keep
my shooting fingers warm. About 40 degrees at 11am. I shot a few strings of 25 of various pellets and then had a lunch break. Turned off the
heater and an hour later resumed shooting. No heater now.
The cocking arm seemed to spring open a bit as I lifted it as though there was some air left in the cylinder. Also seemed to drop the pellet POI
slightly. It went away and came back randomly. Is colder temperatures
affecting a valve release or what? Is it something I can lube differently?
Usually in warmer weather the lever lifts easly and has no jump to it.
Thanks, Phillip

[BM]

Temperature will indeed affect the POI and accuracy of airrifles. On our range we make sure we have the rifle stored in a room with a continuous temperaturecbetween 15 and 17 degrees celsius (roughly 59-62 fahrenheit).
Below this temperature we notice a drop in accuracy from 6mm (10 shot group) to almost 10mm. Small differences but confusing when competing.
The reason? We think that because an airrifle has so many parts and if every part just slighty changes size or seals are thicker it will affect the whole functionality of the rifle.

[robf]

Many things can affect air rifles.

Most stocks including the ally ones warp.

We end up free floating most and running them with polished internals and no lube, with different seal materials to combat the -7 to +40 ambient we can shoot in with FT. Otherwise we can see massive POI shifts.

[yana]

Can very well be temperature.
With my Diana 100 I even noticed differences when I cocked it fast or slowly..

[JSBmatch]

What you describe with the lever jumping back slightly and loss of velocity are the symptoms of a worn/leaking air seal. I have replaced quite few because of this.

JSB

[peashooter]

Do seal problems result in random velocity changes or a steady change in velocity resulting in poi drift? If it is random, if one was to test the velocity on a chrony, what variation in velocity would be the sign of seal problems?

[philip_T]

Thanks all.