Well, not having any luck. Sanding's a no go, need to remove too much plastic and what would be left would be too thin.

Tried the hot water trick, also a no go. Got the water boiling, put the nocks in and let them sit for quite a while, they didn't soften one bit. They are bohning signature nocks, plastic seems very hard.

Does anyone know of a nock that will work with carbon express terminators that have a wider throat?

Found a solution.

Took a flat blade screwdriver. Put it in the nock slot horizontally, and leveraged it both ways to bend the nock fins out then held it for a bit to let things stretch.

Nocks now slip on perfectly, hold an arrow vertically and release it with just a gentle tap.