Head spacing

[Toy Cobra]

How important is it to check head spacing on an AR upper? I bought a NiB bolt and carrier and am not sure if I need to check it. If so where can I buy the gauge to Check it properly?

[LANTIRN]

Pretty important when you are building it; my cousin and I built 3 ARs and one of them failed to headspace properly; turned out to be a barrel out of spec that was quickly replaced by the manufacturer. Had we not checked the headspace bad things could have happened as the tolerance was just slightly too tight and may have gone unnoticed and caused a bigger bang than we wanted. Just google 5.56 headspace guages (or .223 depending on your chambering) and several sites will come up. I can't remember where I bought mine from.

[YALE]

Go/no go gauges are everywhere. Midway USA has them, and Cabela's should have them in stock.

[soap]

I don't even check that shit. I just put together and shoot

[Moose242]

I'm not a big AR guy, but aren't AR15s self headspacing?

[Toy Cobra]

I bought a new PSA complete upper. I am replacing the BCG. Do you think the spacing will change with the new bolt carrier group or should I still check it?

[soap]

I bought a new PSA complete upper. I am replacing the BCG. Do you think the spacing will change with the new bolt carrier group or should I still check it?

Don't check nothing. Just go shoot the thing then take it home clean & oil her. That's it!!!

[Trick Pony]

I don't even check that shit. I just put together and shoot

While I'd agree that if the parts are right then there should be no issue with an AR, it's still a good idea to check when you're putting one together to make sure everything is in spec. The story above about the bad barrel is a good example of why.

[soap]

Just checked mine. The way i did it was with the help of my cow. I lock the bolt back take her tail place the tip of the cow tail in the breach. Then hit the bolt catch slamming the bolt closed. If the cow says moooo!!! Then you may have an issue. If the cow says nothing and doesn't hit you with her tail. Ur good to go

[ThreeFingerPete]

I'm not a big AR guy, but aren't AR15s self headspacing?

If the barrel extension is tight against the barrel and the chamber is in spec, then the head spacing is good. Generally if an AR is out of spec, it's because it's a shitty barrel.

[CJ]

I'm not a big AR guy, but aren't AR15s self headspacing?

Incorrectly manufactured parts are responsible. Not a very common occurrence.

[Chopped54]

Non-issue on ARs

Have never headpsaced any that I have built....

[Trick Pony]

I look at it this way - if you are building your own AR upper and there is a manufacturing defect in a part that creates a situation that could kill or maim you, it's worth using a $25 tool to test it first.