Head Spacing Required

[Gomphe]

Hello All,

I've just recently upgraded my bolt carrier group (BCG) and bought a new Nickel Boron BCG from Spike's Tactical (see picture below) for my AR-15 platform. Now, since my AR is mil speced, do I really need to check the head space for the new BCG? I am hearing conflicting stories (and other questionable information) from different gun folks and gunsmiths.

Some say that it's always good practice to check the head space whenever you replace the BCG. However, it is not really needed, especially if the rifle is and the new BCG are mil speced. Still, I have heard (and I really question this bit of information) that NiB-X lined BCG really needs to be checked for head space; especially after they have been coated with nickel boron. Finally, others say that you will only need to check the head space if you replace the barrel.

So, that being said, is it checking the head space just good practice when replacing a mil speced BCG or is it a requirement? Please help me sort this all out and to determine if there are any truth to what I've been hearing. Thank you all in advance.



- Gomphe

[munkeeboi]

any new mating of bolt/barrel should be checked for proper headspace.

just hearing the stories of coatings that are too thick/thin or tolerances that are not quite mil-spec are enough to make me check headspace everytime.

[Czechsix]

It's never a bad idea to verify headspace. Never.

As to milspec, most folks don't even know what the hell that truly means, it's used mostly as a marketing gimmick these days.

I'll pretty much lay money down that there's no MilSpec class for nickel boron on a M4/M16 bolt though lol.

[SonofWWIIDI]

I would check just to be sure. But that's me.

Better safe than sorry.

[kcstott]

It all comes down to how much you trust your parts suppliers and makers.

That first shot could ruin your day.

Check your headspace.

[VictorFranko]

However, it is not really needed, especially if the rifle is and the new BCG are mil speced.

Let me explain something to you.

Mil-Spec is nothing but a of set standards, including materials, dimensions, tolerances, plating thicknesses, etc. that are SUPPOSED to be adhered to by those in the manufacturing industry when manufacturing parts for the defense industry.
The private sector has adopted these standards in many cases.

Just because something is said to be Mil-Spec, does not mean that it is.
There are shady manufacturers out there and there are shifty machinists who don't want to admit to their boss that they undercut a few parts, so they try to slip them through.
Sometimes things are just plain missed by those in manufacturing and those in inspection.

Have you ever just goofed at work?

Ever made a mistake?

It happens when producing Mil-Spec parts too.

I've seen pretty much everything possible in 36 years of producing Mil-Spec parts for civilian and military aviation, civilian and military satellites and military weapon systems.

[ar15barrels]

is it checking the head space just good practice when replacing a mil speced BCG or is it a requirement?

Checking headspace is the BEST PRACTICE.
You can do whatever you want though.
Feel free to jay walk through rush hour traffic while drunk if it pleases you.

[CC Gunsmithing]

Gee, question if the ONE PLACE that CONTAINS the EXPLOSION in a firearm, Or check it with a set of $50 gauges.. Hmmm

[klewan]

Hold the gun as far as possible over your head. Shoot it. If it doesn't blow up, you're safe. But that doesn't mean the next batch of ammo won't blow up. The thing is with ammo, it can and will have different dimensions. So all of the 'headspace fanatics'; you know whom you are, are giving you somewhat valid info. You can have a chamber that is right on the spec dimension, and still have problems, because the ammo isn't to spec. It would be nice if you shot the headspace gauge, but you don't. This whole headspace mania makes me weary.

[Gomphe]

Well, considering a good majority of the folks I've talked to and according to the varied posters here, I decided to check the head space just for comfort of mind. I complete understand the overabundance of caution when replacing a BCG (even if it was from a very reputable company). Having my AR blow up on me would not make me happy; especially after I had spent some serious bucks upgrading my BCG and a new drop in trigger.

So my next question is, how often should I perform a maintenance head space check on an AR platform - once every 5k or 10k rounds? Thank you all again for the input.

-Gomphe

[ar15barrels]

how often should I perform a maintenance head space check on an AR platform - once every 5k or 10k rounds?

From the military armorer's manual:

ARMY TM 9-1005-319-23&P
AIR FORCE TO 11W3-5-5-42
WARNING
ALL WARNINGS in this technical manual pertain to both the rifle and the carbines unless otherwise specified.
Before starting an inspection, be sure to clear the rifle. Do not pull the trigger until the rifle has been cleared. Inspect the
chamber to ensure that it is empty and no ammunition is in position to be chambered.
Do not keep live ammunition near work area.
To avoid injury to your eyes, use care when removing and installing spring-loaded parts.
All M1 6A2 rifles and M4 carbines must be inspected and gaged at least once annually for safety and serviceability. Initial
gaging is required 1 year from receipt of the weapons. Air Force users refer to inspection requirements in Air Force
Manual (AFM) 36-2227, Volume 1.
All Army Reserve and Army National Guard M16A2 rifles and M4 carbines must be inspected and gaged at least once
every 2 years, after the initial inspection/gaging procedures have been accomplished. This initial gaging procedure is
required 1 year from receipt of the weapons. This 2 year interval may be maintained unless preventive maintenance
checks and services (PMCS) or other physical evidence indicates that an individual unit’s M16A2 rifles and M4 carbines
require inspection/ gaging at a more frequent interval. If it is determined that a yearly inspection is necessary for an
individual unit, only that unit will be affected. This will not affect other units in regard to the interval of inspection.
It is recommended that training units inspect/gage all rifles and carbines at the end of each training cycle. Training units
will inspect/gage all rifles and carbines at least once annually.
Below direct support maintenance, DO NOT interchange bolt assemblies from one rifle/carbine to another. Doing so may
result in injury to, or death of, personnel.
Bolt cam pin must be installed or rifle/carbine will blow up while firing the first round. If the bolt cam pin is not installed,
injury to or death of, personnel may result.
Dry cleaning solvent is flammable and toxic and should be used in a well ventilated area. The use of rubber gloves is
necessary to protect the skin when washing rifle parts.
When using solid film lubricant or dichloromethane, be sure the area is well ventilated.
When using carbon removing compound (item 8, app D), avoid skin contact. If carbon removing compound comes In
contact with the skin, wash thoroughly with running water. using a good lanolin base cream after exposure to the
compound is helpful. Using gloves and protective equipment is required.
The lock plate prevents the selector lever from being placed in BURST and will be installed at the discretion of the unit
commander. It is mandatory for use in civil disturbance (riot control).
Only blank cartridge M200 is to be used when the blank firing attachment is attached to the rifle/carbine.
Change 5 a

I bolded the relevant sections.