I recently built a bull barrel ar with a 556 chamber. I would like to get that reamed to 223 AI. My question is will I still have to option to shoot mil sirp ammo? The reamer would only affect the chamber not the throat correct? So in theory it should be ok for mil surp? Also is this even a good idea the rifle shoots great just looking for more speed. The ideal way to go would be just get a new barrel chambered in 223 AI and build another one. Thanks in advance for your input.
Gunsmithing Reaming 556 NATO chamber to 223 AI
- Thread starter mecher50
- Start date
You would have to set the barrel back one thread and rechamber. It can be done, but it isn't the easy way to do things.
You can't set an AR barrel back. One thread would not do it ether if it were a bolt gun because the straight section is longer than one thread.
Yes you can do an AI reamer into a NATO chamber. It will just have a less than optimum throat in it for accuracy work. The measurement to datum line is the same for 223 SAAMI, 556 NATO, and 223 Match chambers.
Just make sure it is not a chrome lined barrel or you'll ruin the reamer.
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A true 40 degree shoulder AI chamber is .004" to .006" shorter than the standard chamber at the neck/shoulder junction, This is to better hold the case when shooting standard .223 ammunition when fire forming. Which make rechambering an AR barrel already chambered a little problematic. Now you can run a reamer in a little deeper into your barrel insuring the shoulder area is cleaned up, and end up with a custom chamber, which will end up perhaps over stretching the brass when fireforming. A standard AI die set will work, you just have to back the sizing die out just a bit.
One side note, 40 degree AI does not always feed well in an AR.
One side note, 40 degree AI does not always feed well in an AR.
