Chamber size .177

[Deadeye Dick]

I have two air rifles both .177. One is a Diana 48 and the other a Gamo Varmint.
I have been shooting Daisy Flat nosed out of both with no troubles. A couple days ago I tried Piranha 10.5 grain pellets in the Gamo and they were extremely tight to the point that thumbnail pressure to seat them is denting the back end of the skirt, but they still shoot.
I tried the same pellets in my Diana 48 and they slipped right in as intended.
What gives?

 

[Treefrog]

Apparently the leade in spring-piston airguns varies in diameter between model and brand. Pellet heads and skirts also vary.

The Quest won't let me seat most Gamo brand pellets without assistance from a pellet seater. Some from the same tin will go right in while others won't. Crosman and Daisy pellets seem to be more consistent in diameter.

J~