I've had a number of Grendels--one of my favorite AR-platform calibers. I've had so-so accuracy with the SSTs and have found that the ELD-M, Nosler Ballistic Tip and Sierra offerings in the 100 to 120 grain range have worked best for me. 8208XBR is my go-to powder but I've had good success wtih AR-Comp as well. My 24" barreled Radical Firearms upper is a tack driver, but my brother returned a couple of BCA barrels because they shot horribly before finally getting one that was reasonable. Definitely rule out the scope/mount before you start chasing accuracy or you'll just be wasting your time. I've had good success with the Burris PEPR mounts on my scope-equipped ARs.