I’ve reloaded numerous combos for 6.5 Grendel in the hundreds. If velocity is your #1 priority: CFE223 or Leverevolution. Varget works, Benchmark works. However, if you’re trying to eke out small groups with a temp stable powder, IMR8208XBR and AR Comp are the two best. The 8208 is great, but it will spike close to max in heat worse than AR Comp, but both are top 2 IMO. I’ve shot many 5-shot (yes, I know) groups in the .4s and .5s. It’s a Wilson Arms (not to be confused with Combat) fluted H-bar and it shoots really well.
Bullets:
-Hornady 123 ELDM and SSTs. I love ELDs, but the SST in a Grendel just flat shoots and kills.
-Nosler. I bought a boatload of 123 custom comp. and 26.9 gr of ARComp has been a hammer. Shoots 4-4.5” 5-shot groups at 500. Repeatable.
Some like 129 ABLRs, some like 129 SSTs. It’s already a super slow round so I just don’t see the advantage of losing another 100fps.
Next is 100 ELD-VT for non-deer loads.