Get yourself a Rav-Vin micrometer.
These are close copies of the P.J. O'Hare, which are very collectable.
I have both, my Ray-Vin is tighter
There is no way you are going to make any sort of decent elevation adjustments, particularly at 1000 yards with an 03 without this micrometer.
A 1000 yard target frame is supposed to be about 8 feet by 8 feet, but in actual practice it is about 8 inches by 8 inches. You don’t have to be off my much to miss the darn thing.
If the sticker shock hits you, just wait when they go out of production. I have not seen new P. J. O’Hare micrometers since the 60’s. And I don’t think they were made past the 40’s.