Head Space
- Thread starter Collieman
- Start date
basically,headspace is the amout of space between the chambered round and the bolt face.
It is measured,usually depending on if it's rimmed or semi rimmed round,by the space between the bolt face and the shoulder of the cartridge.
Chinese m14 bolts usually have a lot of slack or clearance than a usgi bolt.
It is measured,usually depending on if it's rimmed or semi rimmed round,by the space between the bolt face and the shoulder of the cartridge.
Chinese m14 bolts usually have a lot of slack or clearance than a usgi bolt.
Headspace is roughly measured using a set of precisely machined "plugs" or gauges. They are inserted into the chamber of the rifle and the bolt brought into battery (closed). The extractor and op-rod spring are removed from the rifle. There are two types the SAAMI and the NATO. Each have different measurements for the NOGO.
By definition, headspace is the distance between the bolt face and the rear face of the gauge - with the bolt resting firmly against the receiver lugs and the gauge touching the front of the chamber. Basically, it is the wiggle/stretching room inside the chamber for a casing when the round is fired. Too much space could result in damage to the casing or rifle.
Practically speaking, a gauge is inserted into the chamber (no extractor or springs) and the bolt is slowly brought into battery. If it closes, the rifle passes the first test. If it does not close, the chamber is too tight for SAAMI specs. Next a (SAAMI/NATO) NOGO gauge is inserted. Again the bolt should be brought into battery. If the bolt does not close on either guage, relax the chamber is good. If it closes on the SAAMI but not on a NATO - the chamber is NATO spec'd. This is generally ok, but you will have to be cautious of the commercial 308 brass used and you will have to give some consideration to how you reload the casing.
As a footnote, I had an issue with Win SuperX 308 in my Weatherby, it was measurably smaller the other rounds and I had some issues. So it can happen, does not matter if it is a Norky or not.
... then move onto the next stage.
Insert the FIELD gauge. If the bolt does not close on the SAAMI, again use some caution as the chamber is larger than the SAAMI recommendations, but nothing earth shattering. If the bolt closes on either the SAAMI or NATO Field gauge, I would replace the bolt or bring to a 'smith to look at. I would not be shooting too much commercial ammo in it because it is very likely that the oversized chamber could cause a fatigue in the casing (having to stretch too much) causing a rupture or worst.
My Norky bolt closed on a SAAMI NOGO, but not a NATO NOGO. Turned out I was about .002" from the max. The rifle shot like a dream, etc., etc.
By definition, headspace is the distance between the bolt face and the rear face of the gauge - with the bolt resting firmly against the receiver lugs and the gauge touching the front of the chamber. Basically, it is the wiggle/stretching room inside the chamber for a casing when the round is fired. Too much space could result in damage to the casing or rifle.
Practically speaking, a gauge is inserted into the chamber (no extractor or springs) and the bolt is slowly brought into battery. If it closes, the rifle passes the first test. If it does not close, the chamber is too tight for SAAMI specs. Next a (SAAMI/NATO) NOGO gauge is inserted. Again the bolt should be brought into battery. If the bolt does not close on either guage, relax the chamber is good. If it closes on the SAAMI but not on a NATO - the chamber is NATO spec'd. This is generally ok, but you will have to be cautious of the commercial 308 brass used and you will have to give some consideration to how you reload the casing.
As a footnote, I had an issue with Win SuperX 308 in my Weatherby, it was measurably smaller the other rounds and I had some issues. So it can happen, does not matter if it is a Norky or not.
... then move onto the next stage.
Insert the FIELD gauge. If the bolt does not close on the SAAMI, again use some caution as the chamber is larger than the SAAMI recommendations, but nothing earth shattering. If the bolt closes on either the SAAMI or NATO Field gauge, I would replace the bolt or bring to a 'smith to look at. I would not be shooting too much commercial ammo in it because it is very likely that the oversized chamber could cause a fatigue in the casing (having to stretch too much) causing a rupture or worst.
My Norky bolt closed on a SAAMI NOGO, but not a NATO NOGO. Turned out I was about .002" from the max. The rifle shot like a dream, etc., etc.
Oldsmobiler
CGN Regular
- Location
- Coquitlam, BC
To add more info here is the difference between NATO vs Civilian ammo. You can see on the commercial the datum line is in the middle of the shoulder...but on the military (NATO) round the datum line is at the top of the shoulder start of the neck
Quoted for truth
Lol. I forgot about that one. That's the problem with the internet, just like the wife, when you say something silly, it never forgets.
I did look at brownells. I guess I should have said that I was hoping I would be able to source them within Canada.
Discussions on headspace come up once and a while and can confuse a lot of folks.
The reason headspace... Or better put the reason KNOWING the headspace of your particular rifle's chamber is GOOD is so you can make an educated decision on what ammo goes in your gun.
In these rifles it is case expansion vs chamber size we are concerning ourselves with.
Put .308 commercial ammo, which has softer, thinner walled brass than Nato 7.62 ammo , into a chamber with "excess" headspace, say, OVER 1.640, is not adviseable. Reason for this is that the .308 case, being thinner and softer than nato brass, has too much room to expand and case failures have been known to happen.
For the most part, with the 2009 and newer rifles, the average headspace is well under 1.640 and most are 1.636 to 1.638" , which is regarded by most as just fine for nato and commercial ammo.
Tight chambers getting closer to the commercial .308 match of 1.630" do prolong brass life due to not allowing as much expansion, and some believe a tighter chamber leads to added shooting consistancy down range.
For the vast majority of us, knowing your rifle's headspace allows you to choose which ammunitions are and are not safe for use in your particular rifle.
And it kinda goes without saying, knowing your rifle's headspace and being able measure it accurately is also essential for the reloader.
The reason headspace... Or better put the reason KNOWING the headspace of your particular rifle's chamber is GOOD is so you can make an educated decision on what ammo goes in your gun.
In these rifles it is case expansion vs chamber size we are concerning ourselves with.
Put .308 commercial ammo, which has softer, thinner walled brass than Nato 7.62 ammo , into a chamber with "excess" headspace, say, OVER 1.640, is not adviseable. Reason for this is that the .308 case, being thinner and softer than nato brass, has too much room to expand and case failures have been known to happen.
For the most part, with the 2009 and newer rifles, the average headspace is well under 1.640 and most are 1.636 to 1.638" , which is regarded by most as just fine for nato and commercial ammo.
Tight chambers getting closer to the commercial .308 match of 1.630" do prolong brass life due to not allowing as much expansion, and some believe a tighter chamber leads to added shooting consistancy down range.
For the vast majority of us, knowing your rifle's headspace allows you to choose which ammunitions are and are not safe for use in your particular rifle.
And it kinda goes without saying, knowing your rifle's headspace and being able measure it accurately is also essential for the reloader.
I bought my gauges from Forster. I bought the NATO and SAAMI for my 308. The bonus is that the same gauges can be used for the 243, 260, 338 Fed, 358 and 7mm-08. Gave the money on visa and were at my door in about 10 days. Best investment I made because I was able to detect the excessive win case expansion in a very good Weatherby chamber. I was also able to diagnose a chamber issue in my Rem pump.
