So I got out to the range with the Hi-Point, and went through the barrel lapping procedure. Using Dave Tubbs bullets, I set out some 9 targets made from paper plates with a cross drawn on them with one of those markers the taggers find so handy. The procedure here is to work your way through 50 bullets in 5 sets of 10, each set being a finer abrasive than the one before it. Thorough cleaning is recommended between each group of 10, as well as a very slow rate of fire to avoid heating the barrel.
First off, I shot a baseline target using my own 155gr hand loads. Let me suggest that everything I said about the sight rail on the Hi Point carbine seems to be borne out as I could only get two of five shots onto the first plate at 50 yards. The gun needs a 4X scope that will mount all the way back on the rail where there's some actual support. It shoots way better than this with the iron sights it came with.
Next item is to note that the gun really likes the 180 grain bullets I got from Tubbs. Moving from one target to the next as I went from one set of bullets to the next produced reliable groups of about 2 inches. I forgot my chrony, of course, so I have no velocity data for the 180s but I seem to remember shooting some Wally World 180s and getting 1150-1200 fps. Recoil is noticeably less with the heavier bullets.
Tubbs says that you will notice the improvements as you go in the form of a shinier barrel bore, and easier passage of the bore brush down the barrel. He's absolutely right.
Following the regimen with the lapping, I tried once more with my hand loads. Once bitten, twice shy, I did this at 25 yards. Harsher recoil and all, the first 3 shots grouped under 1 inch. #4 flew wide, and the remaining six grouped about 3 inches below the first four. Did I mention that the sight rail on the Hi Point is structurally very similar to the diving board at the public swimming pool?
I did get some chrony info using another members chrony afterward. My bullets now run some 15 fps faster than before the lapping at about 1365 fps.
Further testing is indicated using a sight that doesn't rely so much on the relatively unsupported front end of the rail. One of those very short 4X "tactical" (black) jobs intended for a shotgun or an AR would seem to be called for. Maybe the Barska red dot, which by now has seen service on half the guns I've got.