I bought a brand new Rockriver Entry Tactical and wanted to install a Picatinny forearm. Unfortunately I didn't read the forums here first and made the mistake of using a barrel vise and a three prong barrel nut wrench. Needless to say, I ended up ruining the Parkerizing on the barrel, stripped teeth off the barrel nut and still didn't get the nut off. Finally I decide to read through the forums here. I learned that I should have used a receiver block instead of a barrel vise and a fully pronged nut wrench. I also read that you should place the upper and barrel in the freezer over night and give it a try in the morning. Well, since I couldn't get a hold of the right tools for a couple weeks, I decided to give the freezer a try. After all, I already screwed up the nut. So this morning I took the barrel out of the freezer and place it in the barrel vise. Aligned the three prong wrench and gave it a good whack. And that's all it took, one whack and then I could spin the nut off with my fingers. Yes I understand I should still get a receiver block and full prong wrench, and I will. But it's nice to know you can rely on the freezer when you're in a jam. Just thought I'd shared the experience. Dave C.