300 Blackout reloading questions?

If you're using converted 5.56 LC brass, you'll need to anneal before shooting since the annealed portion on 5.56 is mostly removed in trimming, but other than that it will last as long as any other rifle caliber of similar design and loading.

As always, as I'm sure you know, individual chamber dimensions and reloading details such as over sizing and loading hot loads, will affect brass life more than the design of the caliber. Semi-autos, and especially over gassed semi-autos, will shorten brass life by beating up the case rim. A stick on cushion on your AR brass deflector will help keep from denting brass as badly.

Don't over swage or over trim the primer pockets of the 5.56 brass, and they should last at least 10-20 loadings or more if you don't oversize them and anneal every 2-3 loads. You can try going longer between annealings, and if you get too many split cases, anneal more often.

The load you chose is an average plinking load. Watch for pressure signs above 16 grains of H110. LC 5.56mm brass usually has a slightly larger capacity than most commercial brass, so you can sometimes squeeze a little more powder in it, as some people have loaded them up to 17 or 18 grains with no over-pressure signs, but start checking at around 16 grain. Work up carefully.

Haven't fire the round but based on it's design I'd wager case life will be similar to that of the .223/5.56 in a semi-auto rifle. There will be others with much more experience with that round who can be more exact with their info.