confused about checking headspace on my ar15

[gsc3zny]

I just put together my second ar15, using a PSA upper without BCG and a BCM BCG. Components are marked .223/5.56, however in looking for a headspace gauge, I am finding out there are 2 different gauge sets, one for .223 and one for 5.56. I will be shooting both and need to know what gauge to buy. Or just check it everytime I switch calibers and buy both? I didn't check the first on I built because I bought it as an assembly

 

[Fishbed77]

Check the barrel markings. If it is a PSA barrel (with either PSA or FN markings), it is most likely 5.56mm.

 

[briansmithwins]

Right, match the headspace gauge to the barrel (chamber) which will most likely be 556 NATO.

You only need to check a new rifle, after changing the bolt or barrel. you can also check it yearly if you're paranoid.

Get a USGI style gauge. Those are 556 NATO and are cut so you don't need to pull the ejector to measure headspace. Makes checking headspace a 30 second job.

BSW

 

[gsc3zny]

Both barrels marked 5.56. So I should go for the 5.56 gauge? will I have to check it for .223 also, or will the 5.56 gauge cover that?

 

[HOOfan_1]

Pretty sure the headspace on .223 and 5.56 is the same...difference is in the throat

 

[rcmodel]

Yes it is.

You need a 5.56 NATO/.223 AR-15 headspace gage.

http://www.brownells.com/gunsmith-t...uges/5-56mm-223-headspace-gauge-prod6646.aspx

rc

 

[Canuck-IL]

Reference for dimension differences ...
http://www.ar15barrels.com/data/headspace.pdf

/Bryan

 

[MistWolf]

The important difference between the 223 and the 5.56 is in the leade. Headpsace gauges cannot measure the leade

 

[mtrmn]

To my knowledge, or lack thereof, headspace gages won't tell you the difference between 5.56 and .223. Headspace should be the same for both.

On AR systems, the parts (barrel, barrel extension, and bolt) are all held to a standard spec during manufacturing and headspace is not adjustable by mere mortals. IT DOES NOT HURT FOR EASING YOUR MIND TO CHECK IT AFTER YOU ASSEMBLE A NEW RIFLE, but under anywhere near normal circumstances it is not necessary. I have checked headspace with gages on every AR kit I've put together, (like a dozen or so) and never had one out of spec. But I checked it anyway. Standard headspace gages will work, but the military ones are easier. Last place I saw those listed was at Fulton Armory.

Now if you want to determine whether or not you have a TRUE 5.56-spec chamber/throat, here's a link to a tool to check it.
http://www.m-guns.com/tools.php
Click on the 223/556 gage.
On the same page there is a reamer that will bring your chamber to TRUE 5.56 specs, but if you don't have problems when you fire it then why fix anything. But it will add to your education by simply reading about these tools and you will have that knowledge in case of troubles later on in your AR-building career.

By always sticking with a 5.56 chambered barrel, the worries about what type ammo is safe/unsafe to use will be null and void. The 5.56 marked barrel should handle both with no trouble.

 

[gsc3zny]

So rcmodel, your saying I just need the field gauge, not the go and go/no go gauges?

 

[HOOfan_1]

Field gauge is longer than the no-go. Since as stated above, you can't adjust the headspace, the field gauge is more important thaa no go gauge. Go gauge really isn't necessary for an AR either

 

[briansmithwins]

The Field gauge is the one you want. If the action closes (by hand, without using the recoil spring) on the Field gauge the rifle is unsafe to shoot because of excess headspace. The Go and No-Go gauges are for setting headspace, which is something you are never going to do on a AR.

BSW