I put together a 10.5" upper with oddball/used parts. The bolt and carrier are new RRA. All went well and the rifle functioned tested fine. So far, it digests Wolf, WWB and 855 like candy.
The trouble started when I tried my reloads. The rifle feeds them, but they go in tight....if you close riding the BH it will stop short of battery. If you drop the bolt-release, the rounds chamber but are stuck in the chamber tightly. To extract, I had to tap the BH with a rubber mallet gently to get them out of the chamber.
Now, I would say that's a long case (improper die adjustment), but the weird thing is this is a well used barrel and upper, and every single one of my other AR's (5 total) eats these reloads up just fine.
Sooooo....thinking I would test the headspace, I used my .223 remington guages (all I have), and the bolt will not close on a max (nogo) guage, which is good. However, on the min (go) guage, the guage chambers but it's tight - about as tight as my reloads. Now, I know there are differences between the .223 SAAMI guages and military, but is the sticky min-guage and indication that my headspace is off?
Not experienced with the AR and headspace, and I've been lucky up till now all my builds have been solid and eaten everything I feed them.