AR15 Measurements – Viking Armory

AR-15 Lower Receiver Diagrams – Working Document

Working Document for the Lower measurements. References Below

Receiver Extension Drawing with pin gauging

AR15 Receiver Extension Technical Diagram

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All Documents posted on this site are for informational use only. If you make ANY modifications to your Weapons based on this site, you do at your own risk! If done incorrectly, you can render you weapon unsafe and / or unusable.

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BCG to Buffer Space Gauge aka 2 Quarter Tool

I think School of the American Rifle started the 2 quarter spacing from the AR15 gas key and the receiver extension. I can not find an exact minimum spacing in the Army TM 9-1005-249-23&P Nov 2008. It makes too much sense for it not to be in there. If someone knows let me know and I will put it in the references.

I never have quarters in my pocket when I am working and if I do I will only have 2, what if I need it to fix a spacing issue? So I came up with this little gem.

It measures 2 quarters / 3.5mm thick and has a few stops to help hold it in place while you are cramming your BCG back trying to get the gauge.

BCG to Buffer Space Gauge aka 2 Quarter Tool with quarters

Stops to help hold it:

Opening to let the BCG slide in:

Showing the gap:

BCG to Buffer Space Gauge aka 2 Quarter Tool in use

Ref:

https://www.usmint.gov/learn/coin-and-medal-programs/coin-specifications

Posted on Thiniverse

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AR-15 Upper Receiver Diagrams – Working Document

I am using this as a working documents to be used as I inspect a rifle.

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iGauging Plug for Firing Pin Protrusion Measurements

I was watching this video from School of the American Rifle: 5 Colt BCG Physicals (Video link starts at 16:06) and noticed that he had to modify one of the included extension shafts of the iGaging Digital Depth Indicator Set so the firing pin would not go into the threaded hole. That got me thinking about printing something up. This is what I came up with.

iGauging Firing Pin Plug01 — iGauging Firing Pin Plug 01

The threaded plugs on the bottom don’t have the ejector notch the the top two have. I like the notched one better. I don’t have to remove the ejector to use. Both are sized to fit snug in the bolt face without getting stuck by the extractor. The plugs also help hold the bolt in place while testing.

The bottom is very smooth and will be able to help you get accurate and constant readings. AR-15 firing pin protrusion should be 0.028 to 0.036 Check out the reference page for more info.

It is difficult for me to hold everything in place to get an accurate reading. I think I will start working on a holder. More to follow.

You can download the 3D printer files HERE.