Guys building my own AR and now working on upper receiver. My biggest question is with headspacing. I understand what I'm measuring for but I don't get how a headspacing tool works. Does head spacing need to be done no matter what? Even if I'm buying an assembled bolt carrier group? That is the only thing I'm a little confused about and I've tried watching video and reading material but just don't get it.
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Head spacing question
- Thread starter visigoth4
- Start date
GO gauge - made to the minimum headspace
NO-GO gauge - made to beyond the max headspace dimension for a newly chambered gun
When they ream the chamber into the back of a barrel blank, the machinist needs to know how far to go into the back of the barrel. That is what the GO gauge is for. If the GO gauge does not go into the chamber, a cartridge wont fit because the chamber is too shallow.
A NO-GO should not fit into a newly chambered gun. If it does, it means the chamber is too long and the cartridge will not be supported by the chamber enough. If the headspace is too large, you can run into problems with ignition because the firing pin does not stick out far enough from the bolt face to light the primer reliably. Also if the chamber headspace is on the large side, it's not good for your brass (it gets blown out too much to fill the chamber) and it also leaves no margin for wear in the parts. The bolt lugs and barrel extension will wear over time and headspace will increase.
If someone is building this for you, they should check the headspace with your bolt. They don't need the whole carrier, just a stripped bolt. It's a liability/reliability/professionalism thing. The real problem is with a used or out of spec bolt or barrel extension.
B
NO-GO gauge - made to beyond the max headspace dimension for a newly chambered gun
When they ream the chamber into the back of a barrel blank, the machinist needs to know how far to go into the back of the barrel. That is what the GO gauge is for. If the GO gauge does not go into the chamber, a cartridge wont fit because the chamber is too shallow.
A NO-GO should not fit into a newly chambered gun. If it does, it means the chamber is too long and the cartridge will not be supported by the chamber enough. If the headspace is too large, you can run into problems with ignition because the firing pin does not stick out far enough from the bolt face to light the primer reliably. Also if the chamber headspace is on the large side, it's not good for your brass (it gets blown out too much to fill the chamber) and it also leaves no margin for wear in the parts. The bolt lugs and barrel extension will wear over time and headspace will increase.
If someone is building this for you, they should check the headspace with your bolt. They don't need the whole carrier, just a stripped bolt. It's a liability/reliability/professionalism thing. The real problem is with a used or out of spec bolt or barrel extension.
B
That made a lot more sense thank you. I'm the one building this myself. The bolt carrier group I was looking to get is a spikes Nickel Boron Carrier Group. Herd some good things about it. For a barrel I was looking to get a stag mil spec 16 inch barrel. The reason I asked was that Stag website listed The barrel with the following:
With headspaced barrel extension...
What does that mean?
With headspaced barrel extension...
What does that mean?
It's sort of like saying water is wet IMO.
They took a bolt that is in spec and used that to HS the barrel extension. If your bolt is similar to the one they used then you should be fine. New stuff should be fine. However every once and a while your run into problems. I just got a chrome bolt that would not close on a GO gauge, although there is more than one GO gauge. The AR-15Barrels.com tech section has this .pdf of all the different HS dimensions.
You might get a better idea of how these things go together by taking a look at this thread.
B
They took a bolt that is in spec and used that to HS the barrel extension. If your bolt is similar to the one they used then you should be fine. New stuff should be fine. However every once and a while your run into problems. I just got a chrome bolt that would not close on a GO gauge, although there is more than one GO gauge. The AR-15Barrels.com tech section has this .pdf of all the different HS dimensions.
You might get a better idea of how these things go together by taking a look at this thread.
B
