Originally Posted by
clandestine
I have experience with AR's that have kaboomed that had short headspace. I checked them and warned the owners before the guns blew up. Sometimes there were often additional issues present that lead to the blown up gun. Ammunition can sometimes be the sole cause as well.
Diagnosing a kaboomed gun afterwards can be impossible in some cases depending on how the parts were damaged. Being conclusive about tolerances with bent and broken parts is often a futile effort. I have experienced success in proving it out in a few cases.
Short headspace can cause reliability issues when the gun gets hot or fouled. It can have extraction issues and failures to go into battery. Not all ammunition is loaded to the same dimensions or pressures so some ammo won't show a problem, and other ammo will. The point of using headspace, throat, and chamber gauges is to ensure the gun will function with a wide diet of factory loaded ammunition. It also ensures the gun will run hot, cold, wet, dry, and so on.
Short headspace can also lead to accuracy issues with some ammo, primer popping, bolt face etching, destroyed brass, and can increase the chances of bolt lug or cam pin hole failures.
Many people assume that a certain brand ensures a part is in tolerance. They fail to understand that the AR is a "recipe" and all the parts are supposed to work as a system. How those parts interface is more important than individual dimensions of a part. Two parts can be made within the plus or minus and still be good, but when mated don't work right or gauge out. This is a tolerance stack issue that people swear won't happen with "quality parts". I see it every day. Why is that? Because I check.
Or you can just run it and hope for the best like many people do.
I'm fine if people don't follow my advice. It's their gun to do what they want.
Im not directing this comment at you, but I'm honestly surprised that members of this well respected forum parrot the same "good enough" advice that other less respectable places do.