Function tested it today! ! ! !
Yes, it kicks just like you're think a .45 caliber would.
I tested it in single shot mode. Something I've wanted to try with ARs for a while. Guess what? After you fire it nothing happens. Oh gosh, Capt Obvious.
I'm glad I got a side bolt. I think 458S may have some feeding issues depending on the magazine and the bullet ogive. I was using Hornady 300gr JHPs which have a flat, short nose. Had to help it a little. I couldn't just pull the bolt back and release it. I will read up on the magazine situation. Seem to remember some magazines need the front lip ground down just a little. I was using a 5 and 10 round metal mags. Next time out I'll try some other styles of magazines.
This was ammo from XCaliber and it averaged 1,880fps with an PF of 564. Impressive. (Black Butterfly on order) I wasn't going for groups since I am using a Romeo 5 and was shooting in an indoor range. I did sight it in, just in case I need to use it before I get the Bushnell 1-4x.
On the way home I stopped by our local prepper place (TruPrep) and was VERY surprised when I discovered they expanded the AR offerings and carry more parts than some on-line places. WOW. 6 different lower manufacturers, lots of every conceivable part, dozens of uppers, barrels & hand guards. You can buy from 3 different manufacturers parts kits, or you can buy every part separately. It is the most parts I've ever seen in a brick and mortar gun store. So an Aero Precision M-Lok hand guard with no rails jumped out at me. Exactly what I had been looking for. $99 w/ barrel nut.