Custom Grip Rules - Smallbore Rifle

[lyoke]

Is there any rules on the design of a grip in NRA or ISSF rule books on the design of the grip for smallbore rifles for the prone or 3 pos events? What about air rifle?

I could only find that they can't rest on the sling or left arm in the ISSF rules. And No part of the pistol grip may be extended or constructed in any
way that would allow it to touch or support the back of the hand. But I did not know if there was anything about dimensions like in pistol.

Thank you for any help.