swap 100gr .243 for 80 or 90gr

I have one unopened box of 100gr Hornady BTSP Interlock, and x98 Norma 100gr FMJ.
I have discovered that 100gr won't group in my 6mm barrel, so I'm keen to swap for something lighter.
Would prefer something similar to BTSP, or something suitable for hunting rather than match bullets.
Prefer not to sell these, Id like to swap box for box.

I've got some 80gn and 90gn Speers (100 of each).

Am fairly local too if you're coming up this way (Ashhurst).

Edit: Let me know if you're interested I can send some photos.