I have a Bushmaster 9mm Carbon 15 rifle that I enjoy shooting. Reasonable accuracy out to 50 yards and all AR goodies fit it. Mine has the quad rail, verticle grip, Aimpoint, and light. The longer barrel (16") really helps the 9mm's punch, and it is reasonably cheap to shoot.
My Bushmaster has only failed me with one brand of ammo. China Sports, I don't remember if it's one word or two, but it was trash. My Sig and the Bushmaster refused to fully chamber the China junk. A Beretta and a 9mm 1911 ran smooth with it though.
I checked the dimensions and they were all in spec, but like I said, it didn't work. There was also an issue of over pressure. The primers didn't set back on firing, but they did flatten out against the bolt face (there was no impact mark from the firing pin in the primer).
The pistols evidently can be a crap shoot, but you hardly ever see a negative comment about the carbines, especially the 9mm version. There is a High Point forum and the folks there seem to be pretty honest about their guns.