.243 AR-10 headspacing

[mljdeckard]

So I am temporarily stuck in a one gunsmith town. I got all the parts together for my AR-10. Nickle BCG by Stoner, barrel and extension by X-Caliber. Local guy puts it in the vise and torques it together. All done.

I ask: "What about headspace and timing?" He says: "You don't really have to worry about that with good parts."

Do I need to worry about it?

 

[BBBBill]

I ask: "What about headspace and timing?" He says: "You don't really have to worry about that with good parts."

Do I need to worry about it?

Timing - not at all. It is not a Browning machine gun or similar.
Headspacing an AR pattern gun is debated by many. While it is true that genuine mil spec parts will probably go together with no issues, verifying correct headspace is always good practice. When you deviate from mil spec it is imperative IMO. And you AR-10 is certainly not mil spec as no mil spec standard has been established for that platform (at least not one that has been released for public use) and the .243 round is not used by the military. Headspace gauges are not expensive to buy and can also be rented or borrowed. Remove the extractor, ejector,and firing pin, insert GO Gauge into chamber, close the bolt GENTLY by hand (no buffer and spring). Repeat with the NO GO gauge. If it checks out you are done and have the peace of mind that it is correct.

 

[Blue68f100]

I've measured several bolts from different mfg, they all vary. I have seen a spread of 0.003" on the bolt face. Take this variation added to a barrel spec and you will have some too short and some too long. By all means check the head space. Now some barrel mfg include a bolt that is matched to the barrel. Some may thing this to be an extra expense but it's the only way to get a precision match chamber if that's what your after, without trying different bolts.

 

[mljdeckard]

I've measured several bolts from different mfg, they all vary. I have seen a spread of 0.003" on the bolt face. Take this variation added to a barrel spec and you will have some too short and some too long. By all means check the head space. Now some barrel mfg include a bolt that is matched to the barrel. Some may thing this to be an extra expense but it's the only way to get a precision match chamber if that's what your after, without trying different bolts.

At the time I ordered it, the matched bolt was unavailable. I will have it looked at.

 

[mljdeckard]

So I posted in one of my local shooting clubs, found a guy who had me drop in and checked it for free, just took a few minutes. Good to have the peace of mind.

 

[Blue68f100]

Good to hear you got it checked and all's good.

 

[fguffey]

New

Good to hear you got it checked and all's good.

This is not a reloading section but a shooter can check the smiths work if they have the ability to measure the length of the case from the datum to the case head. When it comes to measuring the length of the case from the shoulder to the case head the reloader/shooter should be able to use a comparator. When using a comparator the reloader must get into the habit of measuring before and again after. The same goes for sizing; measure before sizing and again after sizing.
F. Guffey

 

[mljdeckard]

That will be a thing. I am away from home right now, but I do plan to run mostly handloads through it when I can.