AR tools

hawk18

I didn't want to high jack Uncle Festers thread, but, my question is:  When you guys are building uppers or swapping barrels or swapping bolts, do you use head space gauges?  I'm fixen to swap out the barrel and hand guard on an AR and have never done that before. 

Hawk

Bigslug

Only always.

Headspace gauges confirm several things for you:

1. The bolt and barrel will be compatible with each other.  You're usually OK using a new bolt and barrel from the same manufacturer, but everybody has a bad day from time to time, and if you're pairing an old of one with a new of another, it's anybody's guess.

2. Whoever put the gun together did it right, at several points in the process.

3. The gun will operate safely.  Excessive headspace in an AR can not only lead to the usual problems of case head separation, but also to primers popping out of pockets and rattling around inside the firearm, where they can jam up the works in several ways.

To do it right, you need a set of three - properly from the same manufacturer, and you'll want to know going in if you're dealing with .223 or 5.56 chamber specs:

1. Field.  This is the biggest, "gun is screwed up" gauge.  If your rifle can lock into battery with that, you've got problems.

2. NO-GO .  Rifle ideally should not chamber this one, but not the end of the world if it does - so long as it does not also chamber the Field gauge.  Be aware that beyond here there be dragons  You'll have shorter brass life and have a higher risk of case head separations on multi-use brass.  Better to find a bolt/barrel combo that locks up properly.

3. GO.  Basically a hardened steel dimensional copy of a live cartridge.

tennmike

Yes. GO and NO GO gauges are the tools that keep your handsome mug from being destroyed. And Bigslug covered the 'why' well. Checking headspace is 5 minutes and a few dollars well spent, and peace of mind is priceless on that first shot!

Jay

I can't say it any better the Bigslug did.  I generally only use No-Go and Field.  Once those are checked, if it'll chamber a live round or a dummy made to correct specs, it's good to go.  I have seen several guns that will chamber a No-Go, but not Field.  In that case, I'll go with it and keep an eye on it.  If it ever chambers a Field, that's a definite stop and don't shoot that gun until it's figured out.  Sometimes just swapping bolts will get it where it needs to be.

hawk18

Thanks guys. Info from people you trust seems better than that found on YouTube. 

Next question:  I'm changing from an unfired .223 Rem bolt and barrel to an unfired 6 mm x 45. According to Pacific Tool and Gauge, the.223 Rem set will work for both cartridges. Do you feel this is correct. 

Hawk

JasonMPD

hawk18 said:

Thanks guys. Info from people you trust seems better than that found on YouTube. 

Next question:  I'm changing from an unfired .223 Rem bolt and barrel to an unfired 6 mm x 45. According to Pacific Tool and Gauge, the.223 Rem set will work for both cartridges. Do you feel this is correct. 

Hawk

Someone who knows will say definitively, but if a cartridge regardless of caliber is identical dimensionally from mid-shoulder to base, they usually headspace identically and the parent cartridge gage would be appropriate. 

JasonMPD

And if PTG says it’s good, it is. They aren’t mucking about. 

tennmike

When buying headspace gauges, the manufacturers list all the cartridges that the particular headspace gauge can be used for. One gauge can be used to gauge several different ones using the same cartridge case with unaltered case shoulder.

Bigslug

I don't know the 6x45, but have dealt with PTG on a number of things.  I'd take their word for it.

hawk18

Thank you gentlemen. I see a set of gauges in my future. Funny thing is, PT&G is four or five miles from my house. I will drive by there tomorrow but will order it and have them ship it. The last time I dropped by and purchased a trigger guard, they had trouble dealing with a face to face transaction. 

Hawk