Rudy,, If you want to use the Green dot, it would be best to use a cast bullet. If not then use the 45 grain Hornady that is made for the hornet. I want to say it is the 2220. The other is the sierra bullets have some for the hornet. Start with 7.5 grains of Green dot and you can go up, to 9 grains( this will work for a 50 grain also) but remember that the purpose is a reduced load. 9 grains give you over 2,000 FPS w/ pressure below 40,000
The other thing is that the reduced loads worked better in a 1-12 twist.
I do know of a load of 5 grains of Green Dot, but it is used with a 61 grain lead cast bullet. Be careful when trying to go real light,, because you might get a bullet stuck in the barrel.
2400 has been good also.
But be careful to NOT crimp or use a tapered crimp.
RCBS-22-55-SP is a good cast bullet for this. If you need to buy cast (if you don't cast ) Then beartooth bullets has some, but Montanna Bullet works will probably be better I like their selection better, I think price is cheaper too. Get them sized to .225