I am wrapping up my first build. Waiting on a stock and trigger guard and then I will post pics.

Aero Precision Lower, CMMG premium LPK, PSA Dissy upper, Tool Craft BCG and the BCM Gunfighter charging handle.

Assembling the lower I watched a ton of build videos and the two best tips I picked up were:

-Pressing in the bolt release pin with a pair of vice grips instead of hammering.

-Using a putty knife to hold down the take down pin detent as I didn't order a clevis pin.

Just wanted to pass those along.

Now that it is technically in operable condition, I was thinking about having a gunsmith check the headspace since the BCG and barrel did not come together. I have read opinions in both directions. I called my preferred LGS and they didnt even let me talk to the smith and were dismissive of my concerns. Thoughts?

I can't even imagine that advice. I would simply not shoot a rifle that did not have its headspace checked. You would be nuts. The parts to do so are really cheap and if you can build it you can do it.

Check and verify the headspace. It's likely to be fine but it's an important safety check that absolutely should never be skipped when building a new rifle.............dj

At minimum I'd recommend checking the headspace with the Brownells Field Gauge. The best case would be to check the headspace with a matched set of gauges.

Yeah, I had been planning on checking it. I was just taken aback when I saw so many people say they never did it or even thought about doing it and 'milspec is milspec' so everything must fit together right.

Even with real mil spec parts the tm checks headspace.
And as an aside you don't have any of those parts.

I don't think it is a big deal on the AR platform. There is a huge difference between an AR with its separate barrel hood mating up to bolt lugs and pretty much every other rifle design.

So, I neither think it is useless to do, nor do I think one would be crazy not to do it. It would be a best practice...but if you assembled 100 w/o checking, I bet they'd all be fine.

I'm sure most combinations would be fine and are, but the reason they make gauges to check this is because when its not fine, its a real problem.
I'll repeat what I said above, you have to nuts to not check your headspace.

A while back I invested in go no-go gauges, I think I got them on Amazon or Brownells. They were not very expensive. Well worth the piece of mind. With them, I did come across a brand new BCG that was out of spec. In the military, we used them on most weapons

Okay, maybe I am an idiot. I have built at least 6 AR rifles from a stripped lower. I then bought the lower parts kit, upper, BCG, barrel, etc. all from different places and put together my rifle. Every rifle has shot perfect with no issues and I did not have the headspace checked or even know this was something to be concerned about. So either I am really lucky, or it is not that big of a deal.

quote:

Okay, maybe I am an idiot.

this. or at least you don't like yourself.
Check the headspace.

I've assembled three and never checked the head space. Now in all three cases I used a factory mated barrel and upper, however I supplied the bcg on all of them. All have been perfect.

FWIW if it isn't checked for headspace after the HPT it doesn't meet MIL–DTL–71186A ( Military Detail Spec) para 3.6.3.2. Link. So the whole "Milspec is Milspec" argument is a little hollow, because last I checked you needed the barrel, barrel extension and bolt to properly check headspace.

I personally think it's testimony to Stoner and the rest of the Armalite team that their design can be so easily assembled with minimal difficulty by laymen with minimal tools.

This message has been edited. Last edited by: CD228,

I've built a bunch and every one has checked out perfectly except that one bolt. Chances are that I'll never see another out of spec combo. It's kind of like the lottery, somebody has to win!

Even if your headspace is out of spec, it doesn't mean that it'll cause immediate problems. Often times the firearm continues to work, accelerating wear and chances of failure.

I have headspace gauges if you're interested. I think they are .223's but I'll check when I get home.

On a side note I used to know the head armorer for the NY National Guard. We were talking about headspace and he told me that in 22 years he never saw an M16 or M4 come out of spec that wasn't massively mistreated. It can happen, but you have to try.

Checking headspace is part of doing the job right and is cheap insurance.