Here is a comparison I did with two types of expanding/deforming x39 ammo. Both rounds were fired through an M70 Century Yugo AK with a 16.25″ barrel. The test medium was a pair of water-soaked phone books (see “Phone Book Ballistics”), and the range was 10 yards.
The small hole on the right was created by a cartridge from DoubleTap Ammo which they call “7.62×39 123gr. Rifle Defense”. It is an American made, brass-cased load using what appears to be a Hornady .308 polymer-tipped bullet. The problem with most US-made x39 ammo is that a .308 bullet is not designed specifically for use in an AK/SKS, which has a .310+ bore. Though you can get away with using a .308, it can result in lost pressure and velocity… could be the reason for the poor expansion. Though I really love many of the other loadings offered by DoubleTap Ammo, this is not one that I can recommend… especially at the immense $1.20/round price range.
The big hole on the left was dug out by a Russian made cartridge from Brown Bear (Barnaul). It is a 125g Jacketed Soft Point bullet in a steel, poly-coated case. This is factory new, good quality non-corrosive ammo… not the old corrosive surplus stuff from who-knows-when. I also had the chance to chrono some of this stuff at the range. It averaged just a hair over 2,400 fps in my M70, and about 1,600 ft/lbs of energy at the muzzle, which is just about perfect for a bullet of this weight. At 300 yards, it still packs more punch than my hottest 10mm Auto loads at the muzzle of my Glock 20. This is great ammo for the price… currently about $225/1000 rounds on the internet.
Both loads fed, fired and ejected flawlessly. However, I am leaning heavily towards the Brown Bear based on better performance at about 1/5 the price. Maybe we can get Mike at DoubleTap to start loading some high-grade x39 with .310’s in the future… I bet they will rock.