Also don't get caught up in the whole 2 thou off the lands nonsense - for those who are happy to experiment (and if you're reloading then you should be) there is often a lot of accuracy to be found a few hundred thou back from the lands.
That's a fair few steps on from the sounds of it and I'd be making sure that everything is clean and well seated in your resizing set up, making sure there's no slop. It would be worth trying the same piece of brass in the FL die and the chamber: sizing, then chambering, then if it's still tight turning the die in another 1/4 or 1/8 turn and trying in the chamber again.
Even if you sacrifice one or two cases this way it's worth it.
You will also be picked up on the use of the term 'head' instead of bullet - in the main everyone knows what you mean as it's a common mistake, but it's akin to a novice mechanic referring to tyres on a car as alloys: "
Yeah mate your car failed it's mot cos one of your alloys is a bit bald so you need two new wheels on the back."
Just out of intrest, what/how much lube are you using to full length size your brass?
My process for some recent new (to me) military 5.56 brass is:
- De cap with a lee universal decapper
- clean in the ultrasonic
- dry (low oven/blow torch)
- uniform primer pockets
- deburr flash holes
- anneal necks
- lube and FL
- trim and deburr/chamfer case mouths
- chamber totally empty case to test and adjust die if needed (usually not)
- prime
- load up
I know that process will be a bit much for some people, but it's only my time and I'd rather have as much consistency from the off, even if it's just cheap/free brass, and actually its so far been excellent stuff, so worth the effort in my opinion.
[/ramble]