Well that’s how hollow points work. Upon impact, the round expands because of that little air pocket it created hitting the target pushes the sides out. Look at pistol hollow points after they were shot through ballistic gel. They practically double in width, making them much more likely to get the job done.
Check out Dick’s. They have ARs made by Troy Industries which are better than any RRA, Stag, S&W, etc… for the price range. Awesome parts on it too.
Keep in mind that if you’re buying this gun for extremely long lasting durability, make sure the barrels are chrome lined (on the inside) and not just stainless. Stainless is more accurate, but won’t last as long.