This is just my opinion, so take it for what it's worth.
If you're willing to spend $300 on a rifle...why not save up a little bit more money and get something quite a bit better? I'm not knocking the capability of the Hi-point rifle...it's got a straight barrel and it goes "boom"...but lets be honest, it's an "Ugly baby" rifle...everyone knows at least one person with an ugly baby who, when viewed by friends & family, people go "ohhhhh.....what a .... cute....baby". I know that sounds very ass hole of me...im just being honest and not sugar coating anything. Plus - regardless of anything else, you *do* get what you pay for where firearms are concerned. Starting with jams, misfeeds, and lack of quality, cheap fire arms are cheap for a reason.
You *will* spend your time defending yourself over and over, and, IMO, you will simply grow to not enjoy owning it.
Also, buy something that will increase with value as time goes on. One thing is guaranteed in this country...people will always pay top dollar for a good gun. Guns *are* an investment, as well as a weapon of self defense, and an item of entertainment. If you can't have all 3 in one package, then you're just collecting...or wasting your money (depending on what sort of gun you buy)
You mentioned you liked the hi-point mainly because it shot cheap ammo. So if that's a key buying point for you, you don't get much cheaper than .22lr. Check out the M&P15-22 MOE 22LR 16" FDE from Smith & Wesson (there are other 15-22's from them there are ~$100 cheaper in the .22 model)
You can buy .22 ammo at your local Wal-mart for about $0.04 a round (my box of 550 cost me $20)
If .22 isn't your thing, and you want something a little beefier, there's lots of mid-range priced AR-15s out there. Going this route, you may sacrifice on quality when compared to a Bushmaster or a Colt, for example, but you're getting a much better rifle than a Hi-Point 9mm.
For example, check out the Doublestar Star-15 .223
Depending on where you go, what you buy, and how much bulk you buy in, you can get .223 anywhere from $0.20 to $0.40 a round (respectively) which is still pretty cheap.
Ammo prices in comparison (from Cheaperthandirt.com buying Tulammo as a reference)
.22 - $0.04
9x19mm - $0.17
.223 - $0.20
So set down with yourself and really think through what it is you want in a rifle. There's lots of variables for you to consider so that you make sure that you'll both enjoy the rifle now, and in the future, for what it is, with no regrets.
Again...just how I approach things when I decide what gun im going to buy next.
Sure a HiPoint is not a Colt 1911, but it isn't meant to be. Just as a '60's VW bug isn't a Cadillac, but it got the job of transportation done and done to the satisfaction of the person driving it.
This is why i'm saying "decide what *you* want in a rifle"
You can go buy an '89 Geo Metro ... that thing gets like 70 mpg or something crazy like that.
*IF* all you need is a vehicle to get across town to work in, sure, it gets the job done, like the VW bug, it's not a Cadillac. It's got a 3 banger, not going to haul much other than a driver and maybe a passenger on a good day.
But, if you're after something to haul your trailer, have fun in, and take out for a night on the town, you'd be happier with the Ford Taurus or Chevy Impala. (don't have to get a cadillac to have fun)
There's nothing wrong with the Geo Metro...it does what it's intended to do. But for a little bit more $$, you can get something "better"...*IF* "better" is what you're after...if you're only interested in the 70+mpg, then seriously go for it, you'll be happy for the duration of the vehicles life.