I am curious if anyone else has come across the same scenario as I have.

When I first got my rifle I used a chrono at a rifle club to test the output and my average fps was 725 with a hw100 with exactly half a cylinder of air using JSB Exacts of the .177 variety. This lead me to think the rifle's energy at the muzzle was around 9.85 FPE. Since then I believe this was not the correct reading.

I have just bought a combro chrony and my curiosity of how my rifle would like other pellets lead me to buy some Bisley Magnums @10.5 ish grains.

When testing these two different pellets through the combro here are my findings (I did 3 sets of 10 pellets of each type to get these averages with a haaf cylinder of air).

JSB Exact Diablo .177 @8.44 grains
786.8 FPS
11.6 FPE (This is more what I was expecting from the rifle!)

Bisley Magnum .177 @10.5 grains
678.5 FPS
10.74 FPE

This seems to buck the trend as most of what I have read, people report to have an increase of anywhere from 0.2 to 2FPE energy when using Bisley Mags!!!

I understand that my rifle must just not like Bisley Mags. I thought the more pointed tip may have played a part in a lower reading from the combro so I tried micro adjustments of the combro's alignment with no noticable change in the readings (apart from one "bad" reading which is reasuring).

There was a noticable drop in POI with the Bisley Magnums but my trusty hw100 is still stupidly accurate with both types of pellet.

Has anybody else experienced this with their rifles?

Rob.