Yesterday I was off and was able to get to the range with the Kel-Tec RDB.
The IOR Valdada 3x25mm scope on the Kel-Tec needed to be zeroed, along with shooting the rifle for the first time. Due to limited time, I was only able to get the scope zeroed at 50 yards, and put only 60 rounds through the rifle. The ammo I shot was 20 rounds of Federal American Eagle .223 55 grain FMJBT and 40 rounds of Prvi Partizan 5.56mm M-193 Ball (55 grain FMJBT, but loaded hotter than .223-spec rounds). I fed the rifle from the Magpul Gen 3 20-round P-Mag that was included with it, and a Gen 1 20 round P-Mag.
The Kel-Tec's manual states that it comes from the factory with the gas system setup to function with M-193 spec ammo. I tested this by initially loading one round, to see if it would lock the bolt back after firing. It did so, and thereafter while I was sighting in, I loaded 3 rounds per magazine.
Sixty rounds isn't anything more than a basic function check but the rifle did work perfectly. The RDB has a 1:7 twist and doesn't seem to care for 55 grain ammo, however. Groups were about 2" to 3" at 50 yards, reminiscent of an AK. I plan to try it with 69 to 75 grain bullets to see if it shoots them more accurately.
The recoil impulse of the long-stroke gas system reminded me of an AK. Unlike an AR-15 or AK, I got absolutely no gun-schmutz in my face, since the top of the action is sealed.
Ejected cases fell at my feet.
Again, 60 rounds isn't much of a test but I was curious to how much fouling got into the gun. When I field stripped it, what fouling that existed was concentrated at the face of the piston and the gas head. (Part 156 in the diagram in the manual, <
https://www.keltecweapons.com/media/catalog/category/rifles/rdb/rdb17_series_manual.pdf>)
I still need to get it back to the range for final zeroing at 100 yards, but my first shooting impressions are encouraging.