The 129gr ABLR (AccuBond Long Range) worked well for me in my SBR Grendel. That bullet is specifically designed to perform at lower velocity which is typically encountered at long range in normal hunting cartridges, hence the name. In my 12.5" barreled 6.5 Grendels, it can be launched about 2200 fps MV, which gives about 900 fps of working velocity envelope before it's going too slow to function well.
In your longer barrel, I'd guess you could do 2400 fps with it, giving you a little more room for comfortable expansion without turning it into a varmint bullet from going too fast.
I've also heard the 123 ELD-M works well on deer, and from what I've seen in testing that's probably true, but I haven't used it on deer myself. I'd expect it to be a bit more explosive and would go for rib shots instead of directly through a shoulder.