Gunsmithing Too LITTLE Headspace?

[Phil3]

I tested the headspace on my newly built my AR15 upper and it may be too little. I would welcome some guidance on what I found.

I am using a Young Manufacturing National Match chrome bolt and Krieger barrel chambered in 223 Remington. I removed the ejector from the bolt, and then reassembled. I used a Forster headspace gauge which is labeled .223 Remington and a dimension of 1.4636". Using this gauge, moderate finger pressure on the bolt results in 40 - 50% lockup. Using two fingers instead of one, and pressing fairly firmly, it does achieve 100% lockup, but it is tight. I can get it unlocked without much trouble.

This is my first AR15 and first time trying to measure headspace, so not sure if it is OK or not. The rifle has never been fired. PMC Bronze 55 grain FMJ ammo chambers more easily than the headspace gauge. The bolt lugs are lubed, barrel chamber clean, as is he gauge and bolt face.

Am I OK, or the headspace really too tight?

- Phil

 

[USMCj]

Re: Too LITTLE Headspace?

Its fine, just shoot the damn thing.

 

[chris112]

Re: Too LITTLE Headspace?

How's it do with the rifle fully assembled?
The problem with your method is does it put the same ammount of pressure on the bolt as the buffer spring does? If not, it won't necessarily close as tight as the assembled rifle.

 

[Phil3]

Re: Too LITTLE Headspace?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: chris112</div><div class="ubbcode-body">How's it do with the rifle fully assembled?
The problem with your method is does it put the same ammount of pressure on the bolt as the buffer spring does? If not, it won't necessarily close as tight as the assembled rifle. </div></div>

From what I have read, the bolt should "easily" close on the GO gauge, without undue pressure, when using the gauges. I didn't try mashing the bolt shut, but it was not closing "easily" either.

- Phil

 

[USMCj]

Re: Too LITTLE Headspace?

Phil, if your headspace guage is not made by the same company as the reamer used to chamber the barrel, chances are it will not give you an accurate measurement of the headspace.

Next time, for your peace of mind, when having a custom barrel chambered for a AR, send the smith the bolt you plan on using so he can set the headspace with that bolt.

 

[Phil3]

Re: Too LITTLE Headspace?

Makes total sense. Will definitely do that next time...and there is a next time coming up (AR-10).

I appreciate your help...first time building an AR, and obviously, a lot to learn.

- Phil

 

[wnroscoe]

Re: Too LITTLE Headspace?

If the bolt closes on a go gauge run it. New unfired brass will be slightly shorter than the Go. Use a small base die when sizing the fired brass and you'll be set.

 

[Outsydlooknin75]

Re: Too LITTLE Headspace?

Like said before ... shoot the damn thing.

 

[Greg Langelius *]

Re: Too LITTLE Headspace?

Questions like this are high among the reasons why I prefer to go with SAAMI chamber specs.

Mainly, it's a matter of having everybody singing from the same page of the hymn book. Misunderstandings become significantly fewer.

By adhering to an accepted universal standard, matters like ammunition compatibility and handloading safety become moot points.

My crystal ball is cloudy, and I find it difficult to anticipate whose hands any particular one of my firearms is going to find its way into, and under what circumstances. I flatly refuse to be a party to creating any potential for an injury that might result from assumptions and misunderstandings.

For example, let's assume that I were to die unexpectedly, and my firearms found their way into the hands of a descendant. Not at all unlikely. I would like to rest easy knowing that I didn't create any time bombs that might hurt that individual. I could never forgive myself if I had.

Greg

 

[Phil3]

Re: Too LITTLE Headspace?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Greg Langelius *</div><div class="ubbcode-body">Questions like this are high among the reasons why I prefer to go with SAAMI chamber specs.

Mainly, it's a matter of having everybody singing from the same page of the hymn book. Misunderstandings become significantly fewer.

By adhering to an accepted universal standard, matters like ammunition compatibility and handloading safety become moot points.

My crystal ball is cloudy, and I find it difficult to anticipate whose hands any particular one of my firearms is going to find its way into, and under what circumstances. I flatly refuse to be a party to creating any potential for an injury that might result from assumptions and misunderstandings.

For example, let's assume that I were to die unexpectedly, and my firearms found their way into the hands of a descendant. Not at all unlikely. I would like to rest easy knowing that I didn't create any time bombs that might hurt that individual. I could never forgive myself if I had.

Greg </div></div>

The chamber, according to Krieger (barrel maker) is .223 Remington SAAMI specs. - Phil

 

[Clark]

Re: Too LITTLE Headspace?

On my lathes, I generally headspace to the brass from the die I will use, but when dealing with my brother and his lathe, I buy the headspace gauge.
I loan him the gauge, and tell him to headspace so the bolt just closes, and we do alright.
Waving my hands and talking does not get through to him.

Bart Bobbit headspaces to just close and then sizes the bass to have .001 or .002" clearance.
http://www.thehighroad.org/showthread.php?t=471703&page=2

 

[Phil3]

Re: Too LITTLE Headspace?

I pulled the extractor (and ejector) and tried this test again. To my surprise, it now closes easily on the GO gauge, but absolutely will not on the NO-GO gauge. Excellent! The extractor certainly DOES make a difference. Another firearms lesson learned.

- Phil

 

[jimurphy]

Re: Too LITTLE Headspace?

If it is a new build, I wouldn't worry. The lugs on the bolt and the barrel extension will lap each other and wear in quickly. I built an AR 10 upper with standard clearance, a year later the headspace was greater than I liked, I set the barrel back one thread to correct it.

 

[BLAWTON]

Re: Too LITTLE Headspace?

LOL like my father always said "Your not shooting the headspace gauge."