Yes, it is the old style with square rear. I have some already made ammo that I use in my 24" AR with 1:12 twist I'm going to try first as I'm hoping it is a standard .625MOA or better like the AR is with those loads as one load, the 40 grain load shoots well in almost every gun it is tried if it has a good barrel. I'll do some other load development later as I get time. One of my favorite things to do is load development.