i had the same idea you had with shooting a 32 h&r out of a 30-30. had one 32 adapter made and it was fun to shoot, but honestly kind of useless, not enough power. had 2 more made, this time using 32-20 brass/chamber. one throated for 100 gr bullets and the second for 200 grainers. the 32-20 has the same internal case capacity as the 300 whisper and the same ballistics. I can download the 32-20 with the short throat to match the 32 h&r and go subsonic with the heavy bullets in the other. I have killed everything from ground squirrels to deer with these in a 17" contender barrel. jim