Acceptable variance in OAL?

Discussion in 'The Ammo Can' started by vash_241987, Jul 10, 2011.

  1. Jul 10, 2011 #1
    vash_241987

    vash_241987 XDTalk 2K Member

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    Well I just got my 9mm 115gr FMRN bullets in yesterday, and did a dry run on expanding, seating, and crimping with just cases and bullets. I'm trying to get as close to the min OAL recommended in my lees 2nd reloading manual of 1.120 with 5.1gr of unique w/ a 115gr jacked bullet. I notice that I would usually get .122 or .119, now I realize that not all bullets are sized the same as I checked them. Is there an acceptable variance in OAL?

     
  2. Jul 10, 2011 #2
    fredj338

    fredj338 XDTalk 10K Member

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    That is well withing the nose shape variation form bullet to bullet, not an issue. When you get to 0.04" variation, things start to change pressure wise.
     
  3. Jul 10, 2011 #3
    highbury

    highbury XDTalk Newbie

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    I tested a few loads today with Unique. Through my 4" XD I found 5.5grs with a COAL of 1.120 to shoot well. I gave myself a +/- .002" tolerance in COAL. I don't know if I am in the wrong with that assumption, so someone please correct me if so. I am just beginning to reload, but I like the results so far. Recoil is a bit more than Wally World Federal, but very manageable.
     
  4. Jul 10, 2011 #4
    vash_241987

    vash_241987 XDTalk 2K Member

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    I did a test run today with 115 gr with 5 of each unique loads 5.0, 5.1, 5.2, 5.3, 5.4, and 5.5 out of my xdm9 4.5. All fed well and OAL ranged from 1.117-1.124. My accuracy sucked at 10yds, I tried my best to get a good rest with a backpack on the trunk of my car, 5.2 gr gave the best grouping.
     
  5. Jul 11, 2011 #5
    mbquimby

    mbquimby XDTalk 3K Member

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    I can't offer you any hard numbers but I can say that there can be as much as .004 variance in ammo that had been exactly the same just by being loaded/unloaded multiple times. I've never had a problem shooting it with amount of variance. TIFWIT
     
  6. Jul 11, 2011 #6
    fredj338

    fredj338 XDTalk 10K Member

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    I can give hard numbers. A variation of 0.004" is easily within the variation for bullet nose shapes. That is like a sheet of paper in diff. Pressure signs do NOT start showing up until you are pushing 0.040", & in some rounds, like the 45acp, not until you get 0.060". I have run chronograph test, same loads just seating deeper. With all things being the same, pressure = velocity. You'll see a very noticeable vel/pressure increase above 0.040" deeper seating & it is not linear. This is for the 357sig as put out by ATK: http://le.atk.com/pdf/357_SIG_Setback_Length-vs-Pressure.pdf
     
  7. Jul 11, 2011 #7
    mbquimby

    mbquimby XDTalk 3K Member

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    I love this site. There is always someone out there with something smart to say. I might just learn something from you clowns. Good info, thanks. Comparing it to a piece of paper puts it into perspective.
     
  8. Jul 12, 2011 #8
    fredj338

    fredj338 XDTalk 10K Member

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    Hmm, your sig line needs to be changed if you are going to toss around "clown" as a term of indearment.:shock:
    FWIW, rechambering certain calibers can cause setback severe enough to cause an over pressure event. You should always check your carrry ammo against factory fresh & make sure the bullet isn't moving.
     
  9. Jul 12, 2011 #9
    mbquimby

    mbquimby XDTalk 3K Member

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    You'll have to excuse my crude term of endearment. It's something I picked up from a Gunny I had. If he called us clowns, we knew we did something right....strange, I know, but habit forming.
     
  10. Jul 12, 2011 #10
    fredj338

    fredj338 XDTalk 10K Member

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    I am only poking fun. You wouldn't add a thanks if you were being condescending, I don't think so anyway.;)
     

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