You need a very tight rifle twist for these - Hornady Sub-X 7.62x39mm 255 Grain Rifle Bullets

I bought these for suppressed pig hunting in an AK platform rifle. After loading a number of them I have concluded: 1. You better have the pistol-length gas tap if you want them to cycle. I didn't find any powder in my supplies that could do it with a standard length gas tap configuration. The bullet takes up most of the case volume and you can't generate enough gas to reliably cycle; 2. Standard rifling twists are no-where close to stabilizing this bullet. It took quite a few failures before I decided to really look at the numbers and determined that I needed a custom barrel to use these bullets. This bullet will stabilize at an 8-9 inch twist rate. A Standard AK has a 19.5 Twist rate. There are lighter bullets that work fine (Less than 130 grain), but the 255 would have been really nice if it wasn't tumbling at 30 yards.