.223 AR Reloading Shoulder Setback

Discussion in 'Reloading' started by iowaelkbum, Oct 19, 2018.

  1. iowaelkbum

    iowaelkbum Well-Known Member

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    Hi everyone. I am reloading for my AR in .223 (it has a 5.56 nato chamber). Using RCBS small base die set. My question is how much should I set my shoulders back? On my 7STW the die is adjusted to basically bump 0-.001 What is the appropriate clearance for the .223, factoring in the difference for the AR platform? All comments appreciated. Thanks
     
  2. bigedp51

    bigedp51 Well-Known Member

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    On a bolt action it is .001 to .002 shoulder bump.
    For a semi-auto it is .003 to .006 shoulder bump.

    The case body should be .003 to .005 smaller in diameter than its fired diameter. This allow the case body to spring back from the chamber walls and extract reliably.

    I only use a small base die when I buy bulk once fired Lake City or range pickup LC brass the first time I size the case. Thereafter I use a standard die, "BUT" chambers and dies vary in size so you should measure the case body diameter before and after sizing. Example, I have a standard Lee .223 full length die that sizes the case more than my RCBS small base die. Meaning smaller in diameter and the amount of shoulder bump with the die adjusted higher.

    [​IMG]
     
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  3. just country

    just country Well-Known Member

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    morning, FL sizing normally will set the shoulder for
    proper chambering. for my ar's I use a competition RCBS
    die set. I FL all of my ar brass, and check for length.
    I use Winchester brass and fed. small match primers.
    justme gbot tum
     
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  4. gohring3006

    gohring3006 Well-Known Member

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    Ive never had a problem with .002” setback for my ARs.
     
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  5. 243winxb

    243winxb Well-Known Member

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    A standard RCBS Fl die will set the correct sizing in a single stage press.

    I have found no need for small base dies loading for many 5.56/223 chambered guns. M16A1 to single shot Contenders.

    Bump .003" But only after getting a correct head to datum measurement. This may take 3 firings of neck sized brass.

    Or set the FL die with a gap of .010" between shell holder and FL die. See if empty sized brass will chamber. Adjust die as needed.

    Don't trust a shell plate on a progressive press to give the same shoulder bump at each station.
    Each station of a progressive press may produce a different head to datum measurement on FL sizing, same die setting. A shell plate deck height problem. .125" is normal
     
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  6. xsn10s

    xsn10s Well-Known Member

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    So far I haven't had any problems just FL resizing with standard RCBS and Hornady dies. But many have found small base dies needed for reliable function. I really like bigedp51's post, sounds good to me.
     
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  7. iowaelkbum

    iowaelkbum Well-Known Member

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    Thanks for all the replies guys! I use a RCBS Rockchucker press. With the shell holder making contact with the die it is giving me a shoulder setback of .007. Should I adjust for .004 as bigedp51 suggested? That seems like the best option. Thanks again guys.
     
  8. xsn10s

    xsn10s Well-Known Member

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    As long as you're using the RBCS shellholder with your RCBS dies your probably fine with the setback. To be honest I never measure the setback on my AR. But as bigedp51 noted I'd check the body diameter by the case head as Ken Waters described in his book. You could do .004" shoulder set back if your body gets sized down also. I generally just do a full size setback and find an accurate load for sagerats.
     
  9. bigedp51

    bigedp51 Well-Known Member

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    I'm using Redding competition shell holders when sizing my "fired" Lake City 5.56 cases in my AR15. I use the plus +.004 shell holder for approximately .003 shoulder bump. If using the standard shell holder with die making hard contact with the shell holder I would have .007 shoulder bump. And remember shoulder bump can vary from die to die, my Lee die can bump the case shoulder back .009 vs .007 for my RCBS small base die.

    As stated above it can take several case firings before the case conforms to actual chamber dimensions. I was surprised this week I took some loaded ammunition sized with a small base die for my AR15 rifle and fired them in my new Ruger .223 Ranch Rifle. The fired cases were .004 to .006 shorter than their sized headspace length after firing. Meaning they ended up shorter with the primer protruding. But the load was a starting load of 24.0 grains of H4895 and a 69 grain Sierra bullet. Meaning the chamber pressure was not high enough to make the case stretch to meet the bolt face.

    Bottom line, cases sized with a small base die will be shorter than cases sized with a standard die. And again the only reason I use a small base die is on bulk once fired Lake City brass I buy fired in a multitude of chambers. And then after firing in my chamber I use a standard .223 full length die

    You can take a new case or a full length resized case and place a fired spent primer in the primer pocket just using your fingers. Then chamber the empty case and let the bolt face seat the primer the rest of the way. Then measure the case length with a comparator gauge and have a very good idea of actual chamber headspace length.

    You can look at item "C" below and see the AR15s chamber is .002 larger than a standard .223 chamber. Meaning the standard .223 sizing die could be considered a small base die due to the larger diameter chamber.

    [​IMG]

    I'm loading for three AR15 rifles, so I use a JP Enterprise chamber gauge that is cut with a finish chamber reamer and smaller in diameter the Wilson or Dillon case gauges. I use this gauge for a plop test to ensure the case diameter has been reduced enough to chamber in any AR15 rifle.

    Below the fired cases when placed in base first will drop in further into the Wilson and Dillon case gauges. Meaning the Wilson and Dillon gauges have a larger body diameter and are primarily checking shoulder location. And the red JP Enterprise is cut smaller in diameter and how I check for case body brass spring back after sizing once fired brass. And yes sometimes once fired brass sized with a standard die will not drop all the way into the JP Enterprise gauge. "BUT" brass sized with a standard die in your chamber should chamber. But you should check the fired case diameter and a sized case diameter because dies do vary in size.

    [​IMG]
     
    Last edited: Oct 20, 2018
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  10. MudRunner2005

    MudRunner2005 Well-Known Member

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  11. bigedp51

    bigedp51 Well-Known Member

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    Mudrunner2005

    My Hornady and RCBS precision Mic case gauges are not calibrated. Meaning if you place a GO gauge in them that are not zeroed.

    If you place a GO gauge in the Whidden case gauge does it actually read zero.

    Example my .223 RCBS Precision Mic reads minus -.004 with a GO gauge in it. And I notice the Whidden gauge below is marked .000 GO and is $5.00 cheaper than the RCBS Precision Mic.

    [​IMG]
     
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  12. xsn10s

    xsn10s Well-Known Member

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    That's good information to know. I just used the Precision Mic to measure shoulder bump. But my AR15's are pretty standard home builds. About 3/8- 1/2 MOA so I just FL resize and shoot. Good information guys. You all must of read "Black Magic".
     
  13. bigedp51

    bigedp51 Well-Known Member

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    Each of my full length .223/5.56 dies below will set the shoulder back different amounts if setup per the dies instructions without adjusting the die for minimum shoulder bump. And three dies are not in the photo because they are never used.

    And again if I set my full length Lee .223 die your way the shoulder would be pushed back .009. And cases fired in a AR15 rifle would be very short lived if sized with that much setback. And this same Lee die will reduce the case diameter "MORE" than my RCBS small base die.

    [​IMG]
     
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  14. MudRunner2005

    MudRunner2005 Well-Known Member

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    I don't have one, so I have no idea. I just knew about the adjustable gauge, and thought it might help.