280AI Necked to 338 Neck Length Question

Discussion in 'Reloading' started by benchracer, Jun 5, 2013.

  1. benchracer

    benchracer Well-Known Member

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    If I necked Nosler Custom 280 AI brass up to .338, how much would it shorten the case neck?

    I have been thinking about making a variation of the 338-06 based on the 280 AI case. It seems to me that it might be pretty slick to set it up so one could use the Nosler brass necked up with no other changes.

    I have never wildcatted anything before, though, so I don't know much about doing this. Any of you experienced wildcatters have any thoughts on this idea?
     
  2. benchracer

    benchracer Well-Known Member

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    While I am waiting for someone to chime in on my first question, here are some more questions:

    If I wanted to load for a .338 wildcat based on the 280AI case, what dies would I need?

    I am thinking a 280AI body die, a 338-06AI neck sizer die, and a 338-06AI bullet seater. Am I in the ballpark? Is there a better way to do this?

    Should I neck up 280 or 280AI brass in steps? If so, how many steps? I have been thinking that I would neck up in two stages: .284 to .308, then .308 to .338. What dies would I need to do that?
     

  3. elkaholic

    elkaholic Well-Known Member

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    It wouldn't shorten the neck, it would lengthen it approx. .043"; or at least the length of the case to the neck/shoulder junction would be .043" longer. The neck length could change somewhat from the sizing process but .043" longer would be the result if you maintained the same cartridge length. I think this is what you are asking?.....Rich
     
  4. elkaholic

    elkaholic Well-Known Member

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    What you are suggesting will work and you likely could do it in one step since you are only changing the neck. Here is what I would do since you are talking custom anyway. Chamber it to 300 Sherman which is a jump up in performance over the A.I. and uses the same brass. I have the reamer and can get you a TWO die bushing set with micrometer seater from Whidden for a little over $200. My Sherman would reach 3000 fps with 200 grain bullets in a 28" barrel.......Rich
     
  5. benchracer

    benchracer Well-Known Member

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    Yes, that is what I was asking. I was looking at the prints for the SAAMI/Nosler version of the 280AI vs the P.O. Ackley version and was doing some rough COAL calculations with the bullets I want to use based on bullet length, neck length, and desired seating depth.

    I had previously understood that if a case is necked down, the neck lengthens, and if it is necked up, the neck shortens. Because of that, I was expecting a shorter neck length than shown on the prints I was looking at.

    I have to admit that I am surprised to learn that necking up to .338 from .284 would produce a longer neck. Without the benefit of actually having done that, I am having some trouble getting my head around that.
     
  6. Technologist

    Technologist Active Member

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    Well the material that used to be in the shoulder has to go somewhere, I suppose.
     
  7. benchracer

    benchracer Well-Known Member

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    Here is the thinking behind what I want this wildcat to do:

    1. I am looking for approximately the following performance levels from a 26" barrel @ 63k-65k psi:

    3050-3100 fps with a Barnes 185g TTSX

    2800-2850 fps with a CE 225g D62

    2600-2650 fps with a Berger 250g Hunting Hybrid

    2. I want to keep the case capacity to a level that favors powders in the 4350 burn rate range. I am hoping that if I do that, RL-17 will work well in my wildcat and provide a velocity advantage that cannot be had in a case capacity that favors the 4831/RL-19 burn rate range. I am probably going to need QL to help me get an idea what case capacity I am really after. That will probably be one of the first items on my shopping list as I plan and research this.

    3. I want to retain the option of using Nosler 280AI brass without fireforming. I might still end up going with Norma 280 brass and fireforming, but it would be nice to be able to skip that step, if desired.

    Here are my questions/concerns with the information regarding using the Sherman reamer:

    Would the .300 Sherman reamer simply need to be fitted with a .338 pilot to produce the desired chamber?

    From what I have been able to find out, the 30-06 and .280 case each have a capacity in the neighborhood of 68 grains, the 280AI capacity is around 73 grains, and the Sherman is around 76 grains. By comparison, the .338WM has a capacity of about 86 grains. As mentioned above, I am interested in bumping capacity enough to gain some velocity, but I want to be careful not to bump it so far that I have to use H4831/RL-19 burn rate powders. I believe that would end up costing me performance, rather than enhance it. My problem is that I don't know where the cutoff in case volume is.

    I assume that going with the .300 Sherman would require me to fireform my brass. Is that correct? Would I need to use the false shoulder technique to do this?

    Where the dies are concerned, I have used a micrometer seater die in the past and never felt that it offered much advantage over my standard Redding dies. Where the bushing die is concerned, I have always been leery about using one because I have read that the bushing dies tend to cause a "doughnut to build up in the case neck. Once again, I have always had excellent results with my standard dies and have never felt the need to manipulate neck tension like the benchrest guys do.

    My bottom line, where dies are concerned, is that I would like to stay with standard type Redding dies. What would I need to do to make that happen? If I stayed with the Nosler 280AI case, would that allow me to use off-the-shelf dies like the ones I mentioned previously?
     
  8. Edd

    Edd Well-Known Member

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    The neck will be about .032" longer when necked up to a .338.

    Necks get shorter when the diameter is decreased and longer when it is increased.
     
  9. benchracer

    benchracer Well-Known Member

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    OK, looks like my understanding of the process is bass ackwards. Thanks for the help! Would the neck need to be trimmed to obtain the proper 2.54" case length following being necked up?
     
    Last edited: Jun 7, 2013
  10. TOM H

    TOM H Well-Known Member

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    If you took 280AI neck it up to 338 that case would hold app 71gr/R-17 to the top of the case mouth and if you filled to the start of the neck it be appr 65.5gr/R-17. The 35 WhelenAI to the top of the case mouth it hold appr 72.gr/R-17 and do same to 30x280AI it hold appr 70.5gr/R-17. A new 280AI case filler to case mouth hold appr 70gr/R-17.

    You going to run pretty close to 338-06AI velocity and I would use 338-06 data as start loads.
     
  11. Edd

    Edd Well-Known Member

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    When you decrease the diameter of the neck, the shoulder becomes longer.

    It becomes longer because it is extended farther forward.

    Extending it forward makes the neck shorter.
     
  12. elkaholic

    elkaholic Well-Known Member

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    Benchracer....I think what is confusing you is you have two different things going on. When you increase the neck size on a case from .284 to .338 the the point of the shoulder/neck junction moves back giving you a longer neck by .040 plus thousandths. On the other hand, necking a case up shortens the OAL a little (.005-.010") and it is all in the neck so you have a net gain of .035", plus or minus, in the neck but the oal is slightly less. Does this make sense? You would not have to trim, in fact, the case oal would be slightly shorter......Rich
     
  13. elkaholic

    elkaholic Well-Known Member

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    You should have no problem getting the velocities that you are looking for. The .338 Sherman would probably hold approx. two more grains than a .300 Sherman which would put it near 79 grains. IMR 4831 would work well as would H4350, RL17 and even up to RL22 with the heavier bullets. You would have to fire form the Sherman by using a false shoulder. If you wanted MAXIMUM velocity gain, the Sherman would do it but if the extra hassle is not worth it to you, the gain would not be that much.......Rich
     
  14. benchracer

    benchracer Well-Known Member

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    Thank you. Your explanation clears things up for me!lightbulb I was thinking about neck length in isolation and trying to relate that to case OAL, which was screwing me up. I knew I needed a conceptual adjustment somewhere, I just couldn't figure out where I was going wrong.