I am not new to firearms, nor shooting, but I am VERY new to the mechanics of firearms, cartridges, and ballistics.
I have been doing research for weeks and I have to admit I still do not completely understand what Head Space is, how to measure it, if I can fix a problem gun with “improper head space”, etc…
Can someone, in plane English explain what head space is? I know I sound really REALLY stupid, and I accept that, but with my screaming baby, and my 1 hour of daylight free time a day, coming up with catchy searches for the M4 search function, and googling, and going to library, and what not isn’t really working for me. I’m new to firearms so all the subject specific cross references in the definitions of Head Space I find just leave me confused.
If you could sum up Head Space in one sentence what would it be?
You will need an ejector removal tool (brownells) and some go/no-go guages(brownells).
Im no expert, but it has to do with distances between the face of the bolt and the case. I think…
If a new bolt from a quality company and a new barrel/extension, you will prob be ok. You should check it out anyway. My LGS wants $25 I think for thi service.
Btw…sorry its not a 1 sentence response. Unless you want a giant run on.
Headspace is the distance from the chamber shoulder to the bolt face. Proper headspace is important because a short chamber can cause feeding issues or give you an unsupported case. Cutting the chamber too deep can give you problems too. It is important that your chamber will accept a minimum headspace gauge and not accept a maximum headspace gauge.
Basically, you want the chamber of the rifle or pistol to be within a certain set distance from the bolt in a rifle or breech face of a pistol. Ammo manufacturers use a set spec so your chamber should be in that spec to match.
There is plenty of info on the web about headspace. Nosler’s website goes into detail about proper headspace. There is more to it than what I have posted but I hope I explained it in a basic way.
Headspace is the distance from the bolt face to a datum point on the shoulder. Or, as defined on the SAAMI website- HEADSPACE
The distance from the face of the closed breech of a firearm to the surface in the chamber on which the cartridge case seats.
Here is a drawing of the SAAMI 223 Remington cartridge (top) and chamber (bottom) specifications
On the chamber drawing, there is a symbol that is a circle with an X in it. That denotes headspace and where it is measured. Length shows it is between 1.4736" max and 1.4636" min.
Headspace is critical. If it is excessive, the cartridge case can stretch and rupture, causing an uncontrolled gas escape and broken parts. If it is too tight, you can have an overpressure situation that may exceed the design limits of the weapon and could eventually result in a kaboom.
I will leave this to the experts here that are far more knowledgeable than I, but I think you should make sure to get a 5.56 gauge for a 5.56
rifle and not a 223 gauge:
I did research on headspace when building my first weapon. My conclusion was if you buy a quality BCG and barrel there’s not much to worry about.
It helps to buy your BCG and barrel from the same company.
Just my .02.
The good news is that, in my experience at least, headspace is rarely wrong.
Most manufacturers actually seem to take it seriously. I’ve always found it amazing all the things that are easy to get right, that they chronically get wrong. But in the case of headspace, which is, well, pretty critical and very easy to screw up, they almost universally get it right. I’m glad about that of course but still find it… surprising.
Headspace does not technically measure distance to the case shoulder, or at least where the shoulder starts and stops, those are dimensions all of their own. The datum, or reference, point for .223 cases is where the shoulder diameter is 0.330 in. It is the distance to this point that headspace measures.
ETA To sum that up for Mac: Headspace is the distance from the bolt face to the datum, or reference point, on the chamber’s shoulder. The datum exists where the shoulder diameter is 0.330in.
Headspace can also refer to the amount the cartridge is able to move back and forth within the chamber. According to the SAAMI drawing, you could say the maximum allowable headspace is 0.014in. This is found by subtracting the dimension for the smallest allowable cartridge from the dimension for the largest allowable chamber. Its interesting to note that the SAAMI drawing also allows for an interference fit between the chamber and the cartridge (Biggest cartridge, smallest chamber).
It is my opinion that it does not matter whether a headspace gage is called out as .223 vs. 5.56 since the difference between the two is in the throat/leade and the headspace gage does not go that far into the chamber. If you want an accurate reading, though, you should look for a true USGI field gage. I say this because I have the Brownells Field gage that is marked 1.4736, the maximum allowable chamber headspace which your bolt should not close on. I measured the gage with the Hornady headspace tool and it measures considerably shorter than 1.4736.
I wouldn’t bother buying a headspace gauge for an AR. You can grab bolts from 5 different makers and there won’t be more than 15 ten thous worth of difference between them.
