Headspace Question

[SOTAR]

Thank you for the information. I understand forensic examination after the failure is difficult.

With all due respect, you are introducing additional variables, particularly throat and chamber dimensions. Neither is checked with a head space gauge.

You are certainly not directing your post at me, the first thing I typed was that headspace should always be checked. That's hardly parroting "good enough".

Andy

Andy,

I should have worded my chamber gauging better. My apologies. I know they are generally separate gauges and processes. It can be done with one gauge but that's not optimal. I own a gauge that does throat, neck, chamber, and headspace in one gauge.

I use those various gauges daily and in my classes. Most people don't think think an AR needs to have headspace checked at all.

[SOTAR]

Click on it.
For some reason;
The go is a--- 1.4636 instead of 1.4646
The No go is- 1.4696 instead of 1.4736

The 1.4636 is a .223 GO.

1.4736 is 5.56 Field.

[AndyLate]

Andy,

I should have worded my chamber gauging better. My apologies. I know they are generally separate gauges and processes. It can be done with one gauge but that's not optimal. I own a gauge that does throat, neck, chamber, and headspace in one gauge.

I use those various gauges daily and in my classes. Most people don't think think an AR needs to have headspace checked at all.

I honestly appreciate your input. Knowing that headspace can cause problems is worlds away from an explanation of the problems you have witnessed. I learned a lot from your post.

Andy

[T2C]

I'm having trouble picturing how a headspace gauge can get wrecked when used on a fully assembled rifle - can you explain further? Thanks!

If the charging handle slips out of your hand or you intentionally release the bolt and allow it to quickly go into full battery, it pounds the headspace gauge. A headspace gauge is a precision ground measuring instrument and slamming it between two metal surfaces can cause undue changes to the gauge. Change the dimensions of the gauge between the base that engages the bolt face and the datum line .002" and you may as well toss it in the trash.

If the gauge is not damaged, you may damage the chamber in the barrel.

[Pressingonward]

Yup, that would definitely have the potential to damage the gauge (or the rifle for that matter). Didn't even consider that someone might try to close the bolt with the buffer spring - when I checked headspace on mine I left the bolt fully assembled, but had the upper released from the rear pin and pivoted open so I could actuate the bolt by hand.

My gauges have a notch cut out for the extractor, but I like the idea of also grinding out a recess for the ejector pin...not that I'll be building enough ARs to justify the time it would take to do it.

[T2C]

Here is my 2 cents.

Debris from the manufacturing process may not be completely removed before assembly at the factory and there may be a small piece of milling somewhere in the bolt assembly. There could be storage grease, oil, etc. somewhere in a slot, nook or cranny on the bolt. Before I assemble a rifle out of new components or install a new component on a rifle already in service, I thoroughly clean it. If I take a new BCG out of a package, I take it completely apart and clean it thoroughly before installation, checking headspace, etc. I've seen low round count rifles fail to eject spent brass and got them up and running by removing the ejector and clearing debris from the bolt where the ejector lives.

Headspace is not a daily check, so I don't mind taking a little extra time when building or rebuilding a firearm. If you just drove from Oregon to Camp Perry and a piece of debris in the BCG fouled the weapon during competition, you are not going to be happy. If you are using the rifle or carbine for self defense, it is even more important you don't have a malfunction.

If I worked in a factory and built 50 rifles per day, I understand that I would not have time to completely disassemble the BCG and clean/inspect it before assembling the firearm. If I am only building or repairing a few rifles per day, I don't mind taking extra steps to reduce the chances of a malfunction during an important moment for the user.