[bobnfl]

I"ve ask a few people with AR's if they headspace when replacing a bolt. I am talking about the entire bolt and carrier. Getting mixed answers. So I am asking, do you or do you just replace the bolt? I have always just rebuilt the bolt.

 

[rogn]

Always a good idea to check headspace. There is an element of danger with excessive headspace. And under the wrong circumstances short headspace could result in firing out of battery.

 

[DirectDrive]

I"ve ask a few people with AR's if they headspace when replacing a bolt. I am talking about the entire bolt and carrier. Getting mixed answers. So I am asking, do you or do you just replace the bolt? I have always just rebuilt the bolt.

On an AR the headspace is set by the barrelmaker when the barrel extension is installed.
That's the "socket" that your bolt locks into.
You can get different values within the safe zone by swapping in various bolts.
Some precision builders will do this.

Many builders don't check headspace on an AR and just use a bolt and barrel from a reputable shop.
You can also buy a matched bolt/barrel set from a reputable shop.

If you're a careful type, like me, you'll want to check headspace for peace of mind.
For that you'll need to get a headspace gauge and carefully follow the procedure.
Here is a link to more AR headspace info that you will find anywhere on the Web :
https://www.ar15.com/forums/ar-15/Headspace__Torque_values__and_Barrel_Break_in/4-315921/?

I use the M16 Field Gauge II from Brownell's
This gauge confirms whether or not a rifle is safe to shoot.

Those building a precision rifle will use a different gauge as outlined in the link above.

 

[RPK Clone]

Nah, I trust Mil-spec.
Wait, what am I saying??

 

[Samuel_Hoggson]

Don't. Dozen M-16 uppers. And a .50 ammo can full of new and used complete bolts/BCGs. No idea what originated where now. But.......stuff's all Colt, except for a handful of FN bolts (they're just as good).

Field gauge is the one. And remember to pull the ejector. Without launching it into outer space. Sounds like fun, launch and subsequent need to replace, both.

 

[jrs93accord]

I will say this. I have built nearly 10 ARs in the past 15 years. I have never checked the headspace. That even includes using newer bolts with nearly 50 year old barrels and older bolts with some newer barrels. That said, I have only had one that would not headspace due to an out-of-spec barrel extension. I replaced the barrel and it works fine.

 

[familyman357]

Here's the thing: you can probably get away without checking headspace. But that's no guarantee and if your rifle should suddenly disassemble with high energy that's on you if you didn't check the headspace.

I would check the headspace. Gauges are cheaper than a barrel... or potentially your eye.

 

[wanderson]

I don’t, not with ARs. I’ve swapped bolts between builds on 5.56, 7.62x39 & 9mm builds.

on any other platform, yea, I’d check headspace.

 

[MD357]

I would. Cheap insurance IMO.

Highly recommend visiting the Youtube channel... "School of the American Rifle."

 

[faawrenchbndr]

I"ve ask a few people with AR's if they headspace when replacing a bolt. I am talking about the entire bolt and carrier. Getting mixed answers. So I am asking, do you or do you just replace the bolt? I have always just rebuilt the bolt.

New bolt with a new barrel.
Use quality parts and there isn’t an issue

 

[Nutty Professor 188]

When I went to Colt armorers school we were taught how to check headspace with go, no-go, and field gauges.
When we asked what to do if one was out of spec the instructor told us to grab another bolt from the armory, install, and check.

I guess they just assumed you have an armory full of bolts.

 

[Big Bird]

The numbers are in your favor NOT to check it. Until they aren't. People win the lottery all the time... Can't win unless you play. Of course its only 58,000 PSI 5 inches from your face and eyes separated by a thin aluminum receiver...what could possibly go wrong?

 

[George Kaplan]

I would. Cheap insurance IMO.

Highly recommend visiting the Youtube channel... "School of the American Rifle."

They lost me on "How to fix a scratch on an AR". Easy. Create another and you'll forget about the first.

 

[MD357]

They lost me on "How to fix a scratch on an AR". Easy. Create another and you'll forget about the first.

Not sure if you're just being obtuse or what, I've never seen a video on scratches? However, there's a metric ton of knowledge on how to spec out an AR.

 

[varget]

always been a kind of grey area IMHO. it works until it doesn't.

 

[cciman]

Getting away with it or doing it properly...depends on which side of those you care to sit on.

There are plenty of internet ninjas who will swear by their preference as the way to do it.

Go and No-go are confusing terms -- use the "Field" gauge.

 

[Khufu]

Getting away with it or doing it properly...depends on which side of those you care to sit on.

There are plenty of internet ninjas who will swear by their preference as the way to do it.

Go and No-go are confusing terms -- use the "Field" gauge.

How is go / no-go confusing.

You are checking min and max.

If you want to know exactly how much headspace you have (or if building to tight chamber spec..and by building I dont mean taking a pre-chambered barrel and extension and attaching to an upper) you need the set of gauges with much smaller increments (the sets with 0.001" increments)

 

[Khufu]

However, there's a metric ton of knowledge on how to spec out an AR.

So 10% more than just a ton of knowledge?

 

[Big Bird]

How is go / no-go confusing.

You are checking min and max.

If you want to know exactly how much headspace you have (or if building to tight chamber spec..and by building I dont mean taking a pre-chambered barrel and extension and attaching to an upper) you need the set of gauges with much smaller increments (the sets with 0.001" increments)

A no go is a superfluous gauge for an AR. The field is the max gauge that matters on an AR and its bigger than a no-go. For that matter a go gauge is not really needed. Because the gun will either chamber a round or it won't. If it won't its obvious its too small.... You really only need a field gauge.

 

[Khufu]

A (civilian) field gauge should be 1.4700. No go should be 1.4670.

The no-go give 0.003 more "allowable error" than the field (or if someone is measuring with a dirty chamber).

A chamber between 1.4640 and 1.4670 has more accuracy potential than 1.4640 to 1.4700 (or military 1.4730). The down side is a tight chamber doesnt have as much tolerance for being dirty.