Quoted:
While calling around to some local smiths to ask about getting my newly built rifle's headspace checked, I ended up calling one shop I have purchased a couple handguns from. Their gunsmith told me that if the barrel extension had the M4 feed ramps done by the factory, then there is no need to check the headspace, because this is really what you are checking for anyway.

Now, I'm no gunsmith or AR expert, but that just doesn't make any sense. The feedramps are behind the bolt, when closed, and would have no effect on the volume of the chamber in front of the bolt face.

Any of you guys have a clue as to what he MAY be referring to? I understand that most modern barrels have no need to check this, but his "excuse" just makes no sense to me. And sounds kind of dangerous that he's the shop's "gunsmith."

Quoted:
While calling around to some local smiths to ask about getting my newly built rifle's headspace checked, I ended up calling one shop I have purchased a couple handguns from. Their gunsmith told me that if the barrel extension had the M4 feed ramps done by the factory, then there is no need to check the headspace, because this is really what you are checking for anyway.

Now, I'm no gunsmith or AR expert, but that just doesn't make any sense. The feedramps are behind the bolt, when closed, and would have no effect on the volume of the chamber in front of the bolt face.

Any of you guys have a clue as to what he MAY be referring to? I understand that most modern barrels have no need to check this, but his "excuse" just makes no sense to me. And sounds kind of dangerous that he's the shop's "gunsmith."

While it is true that the head-space is normally set while the barrel extension (which many times are built with M4 feed-ramps) is torqued to the
(threaded) chamber end of the barrel and then locator pinned and then the gas port drilled is aligned and drilled...

Either that funsmith is not that familiar with AR's or he mis-spoke and did not explain the procedure of head spacing a AR barrel properly...

I have never had a head-space Issue with a AR barrel so far that was factory built from a established barrel manufacturer, so it is rather unlikely
that one winds-up with a Improperly head-spaced AR barrel, but that does not mean it should not be double checked for safety, etc. On rare
occasion you may get a chamber that has been cut a little to short and thus possibly wind-up with a head-space Issue...

So this leaves you with the option of borrowing a set of gauges, purchasing a set, or renting a set or just not worrying about it if you believe that the
barrel manufacturer has good quality control or is very established with a good rep, then you should be fine.

Good luck.