Air leaking past piston rings?

TrailBeast said
The very ends of the ring (at the end gap) will resist that new curve and the pressure against the bore will be higher there than anywhere else in the circumference

Yeah I understand the end effects.. the supposedly even pressure against the rings just stops at the ends, and there is not the pressure beyond the ends to bend that last segment to the new curvature. But I was/am thinking that the end effects don't extend very far into the ring, and those effects exist even if the ring is in its normal sized bore.

AJ/FormS said
The rings are designed to be exactly round at exactly one diameter. You can gap them to whatever you want, and in the hole it was designed for it will still be round.

If you take a too-big ring, one that was designed for a bigger hole than the one you are putting it into, it will want to touch the cylinder walls in about 2 or 3 places. Just put one in a hole sometime,square it up, and make a cardboard plug a little smaller than the hole and drop it onto the ring. Weight it down lightly so it sits on the ring flat. Then shine a light up the hole from the bottom. Shazzam!

May I be so irreverent as to ask if anyone has done this light check? I know I have not.... 'cuz I never put in the wrong sized rings.

It sounds like you are saying that the rings, when loose, out of the bore, are distorted in some fashion and not perfectly circular, and reach a true circular shape just at the right diameter. I never thought of that. If that is the case, then it seems logical if you measured the diameter out of the bore in multiple places, the loose ring would not be a perfect circle. That sounds easy to do.

Well, not sure how much this is helping the OP. I was just not sure about some of the things being said. The end gap procedures described are still of concern.