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Old September 11, 2012, 07:58 PM   #1
freebird53597
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Join Date: July 23, 2012
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FL Sizing for AR15

Hi Guys, great forum, first post. (First of many I assume) Anyway I am new to reloading, I have loaded about 400 rounds of .223 for my rem 700 sps tac, and they have performed excellently. I have been neck sizing and bumping back 1 tho when needed. I am going to start loading some brass for my AR tonight. I have 200 rounds of Hornady brass fired once from my AR. In regards to bumping the shoulder back when I measure the fired cases I am getting headspace readings of 1.454-1.460.(Using Hornady Guage) I know I need to bump the shoulder back around 4 tho but since the averages are so far off I am wondering how I should set up my die. Should I set up to bump back 4 tho off 1.460? If I set up that way will it leave the 1.454's alone or will it bump them back even farther? I am worried about too much headspace on the shorter rounds. Also is that much deviation with fired cases normal? If it makes a difference I will be working up a load on a single stage and then going to progressive once I find one that works.

Thanks in advance!!!!
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Old September 11, 2012, 08:55 PM   #2
mehavey
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Quote:
I am going to start loading some brass for my AR tonight.... regards to bumping the shoulder back
when I measure the fired cases I am getting headspace readings of 1.454-1.460.(Using Hornady Gauge)
...wondering how I should set up my die.
1. The AR unlocks/opens under considerable residual pressure. Any/all fired cases are therefore unlikely to give you true headspace readings.

2. FULL LENGTH RESIZE for the AR (and all gas guns) as a matter of discipline. You are not about to wind up with "excess headspace" since the sizing die is designed to produce SAAMI spec dimensions. If you want target dimensions, measure a commercial/military unfired round and standardize on that.

3. Others might suggest fiddling with things to bump the cases to just clear bolt closure, but not at this stage of the game.


~~~~~~~~~
As point of reference, here's the SAAMI diagram:


Civilian GO 1.4640" (min headspace)
Civilian NOGO 1.4670" (max headspace) -- Note: military NOGO is somewhat longer (FIELD gauge can be 1.4730

If you want to be totally blown away, take a look at how things vary for max:
http://ar15barrels.com/data/headspace.pdf

But remember, your Hornady is a comparator gauge, not an actual true-blue headspace gauge. Take a reading off a commercial round for baseline.

Last edited by mehavey; September 11, 2012 at 09:23 PM.
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Old September 11, 2012, 09:25 PM   #3
freebird53597
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Join Date: July 23, 2012
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Hi Mehavey, Thanks for the great information, and detailed response. I really appeciate it!!!

Most of the commercial stuff I have around measures 1.456 so I will shoot for that.

Thanks again!!

Chris
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