Here is the reply I got from Terry at Thor:

WE MAKE SPECIAL ORDER BULLETS UP TO .5055 DIAMETER. WE JUST DON'T STOCK
THEM.

350gr FPB if they shoot well will do fine.

That is what I am currently shooting and it has done great. Have killed two elk with them. Just like to tinker and there is no tougher bullet out there than the Thor

Txhunter, sadly Bullshop is closing up shop soon, according to a source on MM. I have 400 bullets left in .504 that I use in an UltraMag or I size them down to .501 with a lee die for everything else. The great thing is they fit snug into the omega and krb7 sized down to .501, unlike the loose fitting NEs. I tried paper patching the .504s for the White and it worked great for achieving a snug fit. I haven't tried BH209 with the paper patched conicals, but seems like it might work. Did you ever get the Omega to shoot with anything?

Yes, I heard about Bullshop. A sad and untold story there for sure. My Omega is shooting NEs well since I cut off the QLA but have only shot a handful out to 50 yards. Was going to try and go out today, but started cleaning out my hunting closet since I haven't this decade, and that turned into an all day project!

I had the bright idea to cut the pedals off of some sabots for use as wadding under some 460 conicals. That should provide a good seal for BH209 and give the conical a chance to exit ahead of the gas coming around through the QLA. Just haven't had a chance to try them yet. I will order some Thors in the meantime to see if they might shoot.

I did that once and it seemed to help quite a bit, but when I tried FPBs and they flew well, I haven't done it since.