Eligus,

how well does the rifle shoot with factory, is it better or worse than your home loads?

You seem to be trying every bullet under the sun, but only two powders, if you aren't achieving the results that you are trying to achieve change another variable, but only one at once. Try a slower powder instead of a very fast powder, try several charge weights in small increments, 0.1 or 0.2 gr, pick the best charge weight then change seating lengths.

What is the point of testing a load if you think the barrel is dirty, if the barrel is fouled with a dirty powder you will never get a representative group of what the load is capable of.

What is your cleaning regime?

Has the crown been checked by a smith, is the rifle bedded, are the mounts secure, is the scope known to be good?

Sorry, lots of questions.

If in doubt ditch the Hornet and get a .222, RL7, BLC 2, Benchmark, H4198, H322, H335 or RS X terminator with a 50-52gr bullet set at an appropriate depth will give you better velocity, a better BC bullet and much better groups.