Interesting result using resized AK brass for testing.

[lazyengineer]

I'm the one guy who actually likes 7.62x39 brass. I like the thicker neck wall thickness, myself. That, and I have a surplus of LRP, so it's a good way to use those up. And finally, being "free" brass, great for field trips where brass recovery may be spotty.

That said - as everyone notes, you don't really want to use the exact same load as used with Grendel brass, as you'll pressure spike more. I generally just run cheap 90 TNTs in mine - great combination and that's a very forgiving bullet.

Have fun, thanks for the post!