With the understanding that any question like this hinges almost entirely on your specific purpose/goals/use for your pistol/rifle, (i.e. close range, long[er] range, hunting, plinking, duty, keyboard/IG flexing, SHTF, fun hobby gun) I think this scope would make a terrific choice for an AR in 300 BLK.
The SFP red dot is designed for true 1x use and the FFP MDR-TR6 reticle would be great for stretching it out longer. The FFP also gives you the ability to range your targets and opens up a host of other advantages that I won’t dive into hear, but you might read about them elsewhere to see all the ways it might help you.
In sum, this 1-8 is meant to give you as many advantages of a RDS as possible while also giving you the magnification of a LPVO. It might be most at home on a longer barreled build, a proper 7.62 battle rifle, or even on a hunting rig, but 300 BLK (with iterations ranging from super short 5” barreled AR’s up to more traditional longer barreled bolt action and AR builds) would also be a very cool fit.
This particular version of this scope hasn’t been around for long enough in the US to have seen many reviews, so it’s hard to gauge its particular set of merits in the context of prolonged use and torture testing (please don’t do that to this pretty thing) but the quality and track record of the brand go a long way to vouch for its potential.
Most people will be choosing between this, Leupold’s Mark 8, and the Nightforce ATACR 1-8. Might be worth checking those out. Preferences will vary between reticle, brand loyalty, features (SFP red dot, size, weight, lever feel) and possible variations in end-stage durability (with no relevant differences in durability for 99% of users), and military contract track record. You can’t go wrong between any of them, and this would probably be my choice if I was game for the price tag and the $1,500 spread between this and the NF didn’t steer me to one of the others.
Hope that helps. Have fun with the build.
You don't necessarily need a 1-8 times scope with a 300blk. 300BLK is made for close quarters and a 1-4 or 1-6 would be better. I recommend the vortex viper HD gen 2 E 1-6. fantastic glass for a lot less money than an s&b.
It is difficult to fully answer your question without having more information. What style AR (full size carbine, pistol/sbr, spr/dmr, ect)? What is the intended purpose of the rifle (hunting, cqb/home defense, 3 gun, plinking/range toy, truck gun, prepping, ect)? Are you going to be shooting supersonics or subs? Will it be suppressed? What ranges do you plan on shooting it at? And, to be perfectly honest, this optic would most likely NOT be a good pairing with your 300 blackout, REGARDLESS of any of the above. It is an exorbitantly expensive optic (not to say that the price isn't fair- S&B products are TOP-TIER) that most would be hesitant to use in most situations for fear of damage. It also has their MilDot CC reticle, which does not lend itself well to 300BLK because of drop, ESPECIALLY if you plan on shooting subs. For a 300blk, in a low-power variable optic you should be looking for something with a BDC style reticle.