I know that rifle. Almost bought one myself. It is a piston gun.
I looked briefly. The Pentax gameseeker's reticle looks etched, although I can't find specific information. It is simply too difficult to make if it is not by etching.
Old fashioned reticle is thin metal wires, or even real hairs, attached to the scope internal structure. The attachment, sometimes just blops of glue, is designed to overcome the usual backward acceleration. It would detached if the acceleration is forward. Etched reticles are etched on lens, so it would do better. But forward acceleration may still, although less likely, detach the lens. The safest way is to have scope specifically designed for piston guns. Having said that, I've seen many normal scopes mounted on piston guns. They don't seem to have problems, at least not yet.
-TL
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