Write-up on managing headspace for semi-autos

[ocabj]

I wrote a short article detailing headspace management when resizing for semi-auto rifles.

http://www.inlandshooters.net/index.php?contentid=99

I was inspired to write something on this subject due to the increased amount of case head separations that I have witnessed. Amazingly enough, I have witnessed quite a few in Black Hills blue box remanufactured ammo.

This past weekend, I saw a few different shooters using BH blue and I was able to measure their ammunition and found varying headspace measurements from 1.438" up to 1.450" from box to box (using calipers and Hornady headspace gauge). One shooter had two separate boxes of BH blue, one moly and one naked, and mentioned to me after I got permission to gauge his ammo that the moly box was more difficult to chamber (lots of resistance closing the bolt - Tikka T3 Tactical). That box had ammo had headspace measureing 1.450".

Anyway, hopefully this gives insight on FL resizing for the novice reloaders.

[Prc329]

Very nice write-up. This also can pertain to bolt guns correct?

[wildcard]

That was a good read. Thanks for the write up.

Since I didn't have a tool.. I just came up with my own trial and error method. After noticing that my bolt action had some unwanted resistance when closing, I took the brass and incrementally adjusted the sizing die until the resistance was gone/ minimized. Problem solved. Of course your sizing die has to be under sizing/ buming in the first place. I still think I should just get that tool though..

[ocabj]

Very nice write-up. This also can pertain to bolt guns correct?

Actually, yes, the same concepts would apply if you wanted to set up an FL die for a bolt gun with minimal shoulder bump.

[blacklisted]

Excellent article, now I need to buy more stuff.

[westcoastr]

great article....clean and simple.

1) what about checking/adjusting the rifle's headspace. is there optimum where the brass in not overly worked, but the rounds will still chamber?

2) any thoughts on the RCBS Precision Mic vs the Honady LNL?

[ocabj]

1. Not that I know of. Perhaps someone with professional gunsmithing experience could give more insight into this concept.

2. I've heard the RCBS Precision Mic is a good tool. It can measure headspace as well as overall length of a cartridge based on the ogive. If you want a dedicated tool for a specific cartridge without having to adapt your caliper, then the Precision Mic will work for you. I have separate gauges for headspace and overall length (ogive), both of which will work for several calibers, and both require the use of a caliper. Since I reload for several different cartridges, having the Hornady Headspace Gauge Kit along with my other COL gauges is a better choice and cheaper than buying a Precision Mic for all of the cartridges I load for (i.e. .223 Remington, .308 Winchester, .30-06 Springfield, 7.5x55 Swiss, 6.5x55 Swede, etc.).

[ar15barrels]

2. I've heard the RCBS Precision Mic is a good tool. It can measure headspace as well as overall length of a cartridge based on the ogive. If you want a dedicated tool for a specific cartridge without having to adapt your caliper, then the Precision Mic will work for you.

I have a few RCBS precision mics.
They are good repeatable tools.
I believe them to be more accurate than using a set of calipers and some sort of bushing tool.
They are more expensive though so you have to decide if the potential difference in accuracy is worth it or not.

Most people will only need a couple, say a 223 and a 308 so they would be a wise investment.

[dw1784]

good read, J.

it's also good to have a headspace gage if you reload for seperate guns with the same caliber. I have 3 308's, and all 3 have different headspace and case length measurements. I do it because I want to prolong brass life and keep records of everything. In reality, I'm not experienced enough to appreciate the amount of work involved. FYI, the largest of 3, with measurable run-out on neck and body concentricity of a fireformed case is also the tightest shooting of the three.

[xrMike]

Thanks Jon. I think I understand the whole "headspace" thing now.

Since I only plan to reload for .223, I'm thinking about buying this tool instead (mentioned above) instead of the Hornady tool you used in your article:

http://www.midwayusa.com/eproductpage.exe/showproduct?saleitemid=477756&t=11082005

Can somebody confirm that the above tool will let me to do ALL of the following things:

1) measure the headspace of my existing once-fired brass
2) adjust my full-length resizing die for a .002" shoulder bump from the value determined in #1
3) measure the distance from the breach face to the lands in my rifle
4) adjust my bullet-seating depth to give a .001" setback from the lands (or any other value I want)
5) Will it also measure overall length of finished rounds? If this tool won't do that, will my calipers do it, or do I need another tool?

Thanks.

[ar15barrels]

Can somebody confirm that the above tool will let me to do ALL of the following things:

1) measure the headspace of my existing once-fired brass
2) adjust my full-length resizing die for a .002" shoulder bump from the value determined in #1
3) measure the distance from the breach face to the lands in my rifle
4) adjust my bullet-seating depth to give a .001" setback from the lands (or any other value I want)
5) Will it also measure overall length of finished rounds? If this tool won't do that, will my calipers do it, or do I need another tool?

Thanks.

1 Yes
2 Yes
3 Yes, with limitations as the tool comes with a measuring tool for this, but does not account for different ogive angles.
Perhaps you could change out the arbor in the tool for the actual bullets you will be using to get a more accurate reading.
4 Yes, with within the limitations of the measurements you aquire above.
5 No, this type of tool, or the one in Jon's article will not measure OAL.
You can do that with just calipers.
No other tools required.