I usually don't like to admit mistakes, but I made a big one last night.
I got a couple barrels in the mail this week, so last night I made a little time to fit them.
First off was a mint condition 7.62x39 barrel. It was a little tight for the frame I wanted to lock it up to, which is good, that way I can sand the underlug and make it fit perfect. I get out my "special" dowel rod and my ultra fine autobody sand paper, less than 10 minutes later, it locked up perfect. I added a brand new Pallet wood stock set and it looks like a brand new gun. Very happy with this one.
Next was a .223 shorty barrel. I had one frame left, so the barrel was going to go on this frame no matter what. I go to lock it up and it need a TON of metal taken out of the underlug. I thought, no big deal, at least I do not have to shim it. I started out with a little courser paper than normal to try to take the metal off faster. I started out by checking it every couple of minutes, for the first 30 minutes and it didn't seem like I was getting anywhere. It was getting late and I was getting tired, so I went out to the garage and got my Dremel tool and a bit that fits perfect in the circular underlug groove. I set the Dremel on low and grind for about 5 seconds and check it, still tight, I do it again for about 5-10 seconds and it is still way too tight, I'm talking so tight, that there is a 1/8" gap at the top of the barrel/frame. I thought to myself, I will do this one more time and then finish it by hand. I ran it for another 10 seconds and check it. Now it's way too loose.
Now I have to shim it, which I have never done before. Too be honest, I told myself that I would never shim one of my barrels. I guess I'll look at the "shimming FAQ" again and see which way I think will be the best hold.
So what was the lesson I learned?
When you are getting tired, just quit and pick back up on it when you have time. Don't rush things.