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Posted: 12/9/2009 11:52:30 AM EDT
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I've recently started setting up my dillon 550 for 223 loading and ran into a strange issue. Before resizing and decapping the brass fired in my rifle, I decided to use some range pickup FC brass for trimming adjustments in case I set it too short etc. Not waste my good brass. With my dillon 223 case gauge (before resizing) the base would read high (case sticking out too far, not between the upper and lower marks) So I setup my resizer/decapper die per the instructions, screw it down all the way and back it out half a turn. Lube and resize/decap the case and the case guage would still read the same as before. I tried moving the die up and down a turn either way with the same results. Shouldn't resizing restore the brass to 'spec' dimensions?
Blackops_1. |
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Sounds like you simply don't have the die screwed down far enough. I have also seen a set of dies that were reamed too deep and would not screw down far enough to size the brass.
Try raising the ram all the way up and adjust the die down until it touches the shell plate then back it off a 1/4 turn and size a case and see what happens. ETA: Not knowing the brand dies you are using I cant say for sure but its possible on some dies to have the de-capping rod extended to far and it will prevent the brass from moving far enough into the die to be re-sized. You normally end up bending the de-capping rod in this case. Further ETA: I went and looked at the gap between my shell plate and the die, I dont think you could slip a playing card in the gap. Granted this is on Hornady Projector press with RCBS dies so you setup is going to be different I have to agree a 1/2 turn seems excessive. |
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Yep. Not far enough. Backing my die off a half a turn would definitely leave my brass out of spec.
Run a factory round in your case guage to check it as well. If that checks out, crank the die down. BELIEVE ME! The slightest bit of excess headspace on the brass will choke your rifle up. |
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Ok when I get home I'm definately gona crank the die all the way down to the shellplate and see if that helps. I had
it pretty much there last night and it wasn't helping so maybe the FC brass is too outa whack, like whatever gun fired it had the headspacing way off? I dunno, but it wasn't fired in my rifle. The interesting thing is MY once fired PMC brass, case guages perfect even before resizing!?? I've got some learning to do w/the bottleneck cases 
Blackops_1. eta- Just realized per above I may have the decapper rod set too low also
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As mentioned above the die really needed to be all the way down (hence full length sizing =that ) So
did that and backed the decapper rod out a hair and all's well 
I'm still not sure why my once fired pmc brass is perfect on the case gauge before resizing? Maybe brass needs to be fired a couple times to really grow? I've chrono'd the pmc and its avg.vel is 2817fps out of my AR. Upon closer inspection the pmc is just the slightest sliver high outside the case gauge's boundaries, can only detect it with a fingernail and not the eye.. Blackops_1. |
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Quoted:
Glad you got it worked out....Not a clue on the PMC brass...fired in a really tight chamber is the only thing I can think of... Thats what I was thinking also, its a cmmg middy upper U-1605L7 which is supposed to have a 5.56 nato chamber, guess she's on the tight side 
Blackops_1. |
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Ok I've now discovered the brass working range for my resizing operation using my dillon 550b and hornady custom grade new-dimension FL sizer die. With the die practically on the shellplate and with no further adjustments made, I resize/decap the brass and measuring from the case head to the shoulder using my rcbs precision mic the range is 1.4646 to 1.4686. Which falls under the headspace range listed in the rcbs p.m. instructions 1.4636 to 1.4736. I Really wish I could have each piece of brass come out closer to the same but apparently the slop in the toolhead, varying amounts of lube/friction and tolerances of the brass itself creates the difference? Some of the same pmc brass stretchs more than others during the resizing op! It was driving me nuts that some of the brass was that much shorter than the others till I used the precision mic on factory ammo and found it was the same way, actually shorter than the min listed 1.4636! At least if I've understood everything above correctly, feel free to correct me if anyone sees something I don't.
Blackops_1. |
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Quoted:
I would say you just went up a steep learning curve and you're on the right track. But, I didn't notice any measurements of cases sized to function in your rifle. Thanks, I'm slowly learning Some other things I've learned
Don't Crowd Cartridge Case Trim Length My rifle's Cmmg 5.56 nato chamber average distance from the cartridge case neck relief step to the closed bolt face is 1.7800. Average of 10 measurements. Cases are supposed to be trimmed when they grow to 1.760 down to 1.750, maybe I could wait a little over 1.760? Probably not a good idea thou would cut into reliability and this is my home defense rifle.
My dillon RT1200 trimmer consistently trims to within 2 thousandths of 1.750. After resizing/decapping with the aforementioned hornady die, the shoulder is bumped back .001 to .005 thousandths more than before resizing, so the distance from the case head to the shoulder is between 1.4646 to 1.4686. Any other measurements needed? I wish the rcbs precision mic had a provision to measure the distance from the bolt face to where the shoulder contacts the chamber! That would be the cat's meow because then I could determine precisely how far back to bump the shoulder if I knew the ideal amount? What is recommended 3-5 thousandths? I feel there is something eluding me on determining how far back to bump the shoulder? Even though the brass falls within the guidelines the dillon .223 case gauge dictates. I still want to setup my dies etc.. perfect the first time and leave them so they will extend case life. Not trying to set any records in how often I reload the same case, but minimizing case stretch also maximizes safety as you know
Blackops_1. eta- post 1.470 also falls within guidelines 
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I'ts been my experience that different brands of cases will resize differently. If you set the die up to correctly resize Federal brass it may need minor adjustments to correctly resize Lake City. Usually these differences are in the neighborhood of .003" to .004". Double check the resizing process when changing case brands before running a large batch. It has to do with the brass' composition, hardness and thickness. Some cases resize easily, some resist the process. Only measuring will tell.
I resize all my brass to .004" shorter than fired length. I use the tightest chambered rifle that I own, this allows the brass to be used across the board. Ideally brass should be sepereated and used for just one rifle. Unless you are shooting 600+ yard tournaments this is a pain to keep straight. |
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Good points BP, thanks! Always good to sort brass and use in the same gun as much as possible. And 4 thousandths sounds good to me to.
Thinking a little more about the ability to gauge the distance from the bolt face to the shoulder...we really don't need a gauge for that since we measure the brass w/the rcbs precision mic, and the brass stops when it hits the chamber 
Blackops_1. |
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