I recently bought the Gamo TAC Whisper and after installing the Hammer 3-9x40 scope, I decided to sight it in and check the velocity with my chrony. The rifle is stamped with a 1250 fps with a PBA pellet which from what I can tell is about 5.4 grains. When I bought the rifle I picked up some Crossman Ultra Magnum round nose 10.5 gr pellets which actually weigh closer to 10.05 grains.
My first shot was 718 fps - and I realize I'm using almost twice as heavy a pellet. But the next consecutive shots were 684, 667, and finally 660. I understand some variance but I'm concerned about the continual drop in velocity - albeit only 4 shots. I could never find anything as far as lubrication or cleaning, but more along the line as just leave it alone.
Is the drop in velocity just a fluke or a pattern? Thanks.
My first shot was 718 fps - and I realize I'm using almost twice as heavy a pellet. But the next consecutive shots were 684, 667, and finally 660. I understand some variance but I'm concerned about the continual drop in velocity - albeit only 4 shots. I could never find anything as far as lubrication or cleaning, but more along the line as just leave it alone.
Is the drop in velocity just a fluke or a pattern? Thanks.
Most brands are very optimistic about the muzzle velocity and mostly test them with very light/PBA pellets because they are likely to fly faster with the same amount of propulsion force than regular lead pellets. So probably its a pattern.