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Case overall length "COL" 223 75 grn Hornady A-Max - Dangerous Pressure?

Discussion in 'Ammunition & Reloading' started by Remadl700, Dec 3, 2011.

  1. Remadl700

    Remadl700 Oregon Member

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    I am using Ramshot TAC powder and loading to starting spec load in the Ramshot book for a 75 grn HPBT because that is the closest I could come to in load spec for the A-Max bullet. The printed COL is 2.260 which allows it to be loaded in a standard AR15 mag. The Hornady manual states a COL of 2.390 for the 75 A-Max bullet and 2.260 for the 75 HPBT. The A-max is a longer bullet and would require it to be seated very deep and crimped very high up the Ogive of the bullet in order to achieve a COL of 2.26.

    Question: Won't this cause the pressure to spike? Is it safe to crimp that far up the Ogive?

    The Ramshot response was that it is fine to load that deep in order to obtain a COL of 2.260.

    I have some years of reloading experience that consists of success's and some "Boo Boo's". I have also learned to follow my gut on some things and to double and triple check my work and information.

    So I am throwing this out to the forum while waiting for a more precise response from Ramshot.
     
  2. the4thshake

    the4thshake Portland Active Member

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    The A-max is too long to be seated mag length. If you want to shoot them in an AR they need to be single fed. Seating the bullet out close to the lands tends to be more accurate as well.

    I found ,when using TAC with 75-77 gr bullets, it took a bit more then what is publishied to achive the velocity claimed. Pressure signs were nonexistant even at the higher then recomended charges of powder. TAC meters like water but is a bit temp sensitive. I have had better accuracy with stick powders. Try RL-15, Varget or H4895.
     
  3. deadshot2

    deadshot2 NW Quadrant WA State Well-Known Member

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    Ogive-

    "In ballistics or aerodynamics, an ogive is a pointed, curved surface mainly used to form the approximately streamlined nose of a bullet or other projectile."

    First, I don't think you are crimping on the "Ogive". More likely than not, on the bearing surface or the part of the bullet where the sides are parallel.

    Other than that the4thshake has pretty much covered it.

    You didn't mention what twist rate your AR barrel has. If too low, the issue of the 75 gr. bullet may be moot. Even with a safe load/length it might not shoot worth a darn. If a 1:12 twist you'd be better off with a lighter bullet such as the 55gr or 62 gr. I
     
  4. mjbskwim

    mjbskwim Salmon,Idaho Well-Known Member

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    If the 75ers aren't on the "ogive" then you can't measure the difference.They sure look like they are past the parallelagraham (yeah I know it isn't a word)
    I was also wondering this,but I was just gunna try it in the heavy AR.I don't think I seated them short enough to fit the mag. May need to single load.

    Mine is a 1-8 and has done well with most bullet weights so far.Looking forward to trying these.

    Hey 700 could you hurry up and try those....and get back to us? I mean if you don't we'll under stand (and I'll be pulling some bullets ;)
     
  5. Remadl700

    Remadl700 Oregon Member

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    I haven't had enough coffee to get into a semantics discussion on this. I am referring to the curved surface "Ogive" that leads to the tip. The question is that will crimping on the curved surface that close to the tip create a pressure spike that is past the limits of safety for this round?

    I will try a series tonight off consecutive rounds with the bullet seated deeper each time and get back to everyone.
     
  6. Remadl700

    Remadl700 Oregon Member

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    I am using a Dillion 550 and need a powder like TAC. Your right it meters great! The rounds I am putting together right now are for training and 3 gun use, so I am not going for perfection on the rounds but more towards 100% operational and volume. So far they have done well. The one issue I ran into a couple of times was one round stove piping on top of another round that was being stripped from the mag. As if the extractor wasn't letting go of the case 100% and carrying it forward while picking up another round and then obviously jamming as the round pushes up the feed ramps.

    Full auto there have been no problems! These are used assorted NATO brass rounds. I did not pull the rounds that stove piped which I should have done to start my investigation into this and that is where I will start from tonight to see if it's a case issue before moving to the extractor unless someone has a better idea of what's going on.
     
  7. Remadl700

    Remadl700 Oregon Member

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    I just got my email answered from Ramshot.

    The Ballistician for Ramshot, Johan Loubser replied back on the question about seating depth of the A-Max 75 grain round in a 223.

    He stated that it will work seating it to a depth of 2.260 with the TAC powder.

    So, head to the range and we will see how they work and accuracy.
     
    mjbskwim and (deleted member) like this.
  8. deadshot2

    deadshot2 NW Quadrant WA State Well-Known Member

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    Doing so would probably only be seen by the powder charge as a heavier than normal crimp. According to Richard Lee in his 2nd Edition, rounds he tested with and without heavy crimps didn't vary in pressure by more than a couple hundred pounds. That brass isn't really going to slow down the bullet much and cause dangerous pressures unless you are not only over the published max and have used up all the available safety margin.
     
  9. mortre

    mortre Yelm, WA Active Member

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    How did this work out for you? Those bullets didn't work at all for me in the 1/9" barrel of my LTR. They weren't keyholing, but accuracy just wasn't there. 2-3" groups at 100 yards with both H-4895 and 748 I think was the other powder I tried. The only thing I have with a faster twist is an AR, but never felt comfortable loading them to mag length. Did you check if there was any bullet setback when chambering a round?