Too much jump?

Discussion in 'Reloading' started by Iclimb, Aug 4, 2013.

  1. Iclimb

    Iclimb Well-Known Member

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    How much jump is too much jump? I'm shooting a savage 111 long-range hunter in 7 mm. I measured my total overall length and I can run 3.421 COAL. When I load to bergers specifications, i'm coming up with the jump of .136 in my rifle

    I've shot some handloads that are to berger specs lengthwise they seem to shoot really nice conversely I've shot HSM which puts the bullet closer to the LANs, can't remember the specific dimensions they didn't group so well.

    Anyways I know there's more to consider than just the jump between these two, accuracy wise. I plan to do the test recommended in the berger manual, but if this gun likes jump, where is the limit?

    Also if anybody has any load data for this gun I would love to compare some notes.

    Just started into reloading and as I thought I'm falling deep down the rabbit hole, I can never do anything in moderation.
     
    Last edited: Aug 4, 2013
  2. wild_musk

    wild_musk Member

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    I'm right with you on figuring this out, but I think you have to consider that the more jump you have, the less case capacity you have. Less case capacity = higher pressure for a given amount of powder, equals wasted potential. Check your Berger manual for another article by Litz that talks about taking advantage of longer throat lengths - the longer you can load your bullet before hitting the lands, the more case volume - larger volume allows increased powder charge (and velocity) without increasing pressure as much. The lower you seat the bullet into the case, the more you reduce the theoretical maximum velocity for the components you select. Ideally, I *think* you'd like a powder that fills the case 100% and burns 100% as the bullet travels down your bore, yields maximum velocity over all other powders with an acceptable pressure, AND that such a recipe yields a bullet velocity that miraculously equates to your barrel's natural harmonic "node." If I could get those variables to line up for all my rifles, I think I'd be cooking with grease...I suppose you could offset the lower case capacity with a faster burning powder? I'm over my head though...

    On the other hand, when you go the opposite direction and seat a bullet into the lands, you can create a pressure spike, or so my reloading manuals tell me (including the Berger). Wilderness Means suggests always developing max loads with bullets seated .01" into the lands for this reason - good info on his web page, just Google.

    Bottom line, if your case neck goes beyond your bullet's ogive, I'd say you went too far:) If anyone sees anything "crazy" in my spiel, please advise and correct! Good luck!
     

  3. varmintH8R

    varmintH8R Well-Known Member

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    I follow the lead of the rifle. If it shoots best at loading manual OALs, that's where I'd run her. My practical experience is that usually 10 to 50 thou is the range I end up in. I do have a rifle that only likes Bergers at 0.145". That's where I load it!
     
  4. Mikecr

    Mikecr Well-Known Member

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    The answer to "How much jump is too much jump?" is the same as for "how much jam is too much jam?". 'Too much' of any setting is that which produces worst accuracy than just right.

    For long range hunting your focus should be on accuracy, and not maximum velocity or book values(which are meaningless).
     
  5. Iclimb

    Iclimb Well-Known Member

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    I agree I could care less about speed as of the moment looking for consistenct and accuracy I'll adjust for whatever velocity the combo yields. I guess I was mostly concerned if too much jump, seating the bullet too far back would create a dangerous situation in the gun besides pressures of course.
     
  6. Mikecr

    Mikecr Well-Known Member

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    Is your setting putting bullet bearing into neck-shoulder junction?
     
  7. SidecarFlip

    SidecarFlip Well-Known Member

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    Interesting subject. IMO, whatever the rifle likes up to the point where you can't load them in your magazine anymore. My Savage 308 likes the standard COAL whereas my 338 likes them long, to the point where they just fit the magazine. There are guys on here that load their 338's to the lands but that eliminates the magazine and makes the rifle a single feed. Myself, I like the option of 5 in the magazine and one in the chamber.

    My rule of thuimb is load ladder a test group and seat at different lengths to see what your particular weapon likes.
     
  8. Iclimb

    Iclimb Well-Known Member

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    Forgive my ignorance but I don't quite understand that question. I'm a noob to reloading. I understand the neck-shoulder junction, not positive on the bullet bearing; is that where the lands first contact the bullet?

    I just measured my overall length that my gun could handle, 3.441 bullet in the lands. The recommended overall length in the berger manual, 3.290 is yielding a jump of .151 already. Now as I understand it I need to set the bullet in the lands and work back per the berger manual, which suggests anything from touching to .150 off the lands.
    if my groups keep getting better further back at what point do you stop? Is there such a thing as too much jump IE never go more than .XXX off the lands?

    I am contemplating taking the HSM ammo and pulling the bullets, then re-seating them from on the lands to the recommended COAL in the berger manual. Would I have any problems with this method? I would think seating the bullet longer than the HSM coal would be fine i.e. no pressure problems. Now seating the bullet deeper from the HSM Coal; would that create more pressure and not be advised? It would look like this.

    HSM AMMO 66.0gr (?) not sure what they use for powder primer.
    3.291 (-.060) ---berger recommended coal
    3.311 (-.040)
    3.351 (0.000)---HSM stock coal
    3.391 (+.040)
    3.431 (+.080)
    3.441 (+.090)--- rifle max coal

    I'm shooting a handload at 3.290 and it shoots very nice. The only data I'm trying to gather from the above test is to see if the HSM ammo, which is mediocre in my rifle, gains any accuracy that is consistent with the coal that I'm seeing with the handloads. This should give me an idea of where my gun likes the berger bullets. So that when I begin handloading I will know where to start with seating depth. Plus I had two boxes of HSM ammo I need to shoot up.

    The COAL of the HSM ammo happens to fall in line with the seating depth test that burger recommends performing in the rifle.

    I hope this is not too confusing and I can get an answer. I hope I'm not showing my ignorance.

    Thanks, Jake
     
  9. SidecarFlip

    SidecarFlip Well-Known Member

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    If you pull them you have to resize the neck, bullet tension will be lost.
     
  10. Iclimb

    Iclimb Well-Known Member

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    Stock HSM neck diameter .309
    HSM pulled and reseated dia .309
    Fired brass neck dia .313

    With neck diameters being equal would I still have lots of neck tension?