Trick to jumping bullets???

Discussion in 'Reloading' started by tim jurczak, Jul 15, 2011.

  1. tim jurczak

    tim jurczak Well-Known Member

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    So far loading my 6.5 STW to 3.645 ( mag length) has meant jumping bullets 40 to 70 thousands. Have shot two groups under an inch but all others larger. I am assuming this is because of the jump?? What I find myself wondering is could there be a trick such as more than normal neck tension or maybe a lighter than normal load or just deal with it. Please help my stress! Tim
     
  2. fj40mojo

    fj40mojo Well-Known Member

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    If your action is a push feed you can try single loading and eliminate the need to load to mag length and allowing you to seat out to or near the lands and see if your groups don't tighten up. If this isn't possible and you are shooting a controlled round feed action and must feed out of the magazine I'd suggest neck sizing for starters and checking your loaded ammo for concentricity. Allignment between bore and loaded round in the chamber is critical when jumping the bullet.
     

  3. loosesniper2000

    loosesniper2000 Well-Known Member

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    70 thousandths is a long jump. Your stuck with one of 2 options. Stick with what you have and deal with concentricity issues or do something like installing a Davidson loading ramp. You'll convert it to a single shot but it should improve accuracy. I'd try some loads seated out a little further before installing it and go from there.
    It's either the comfort of having a mag or accuracy.
     
  4. Tikkamike

    Tikkamike Well-Known Member

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    Weatherby's have thaw same problem a lot of times. He's is a solution I would try first. Buy a box of Barnes ttsx or lrx (long range x bullet) load them to fit your magazine and I bet you see an improvement in group size. Barnes reccomends starting .050 off the lans and in my experience shoot very well seated way off them. I have seen them tale a 3/4" gun And turn it into a 1/4 "gun.
     
  5. Gunpoor

    Gunpoor Well-Known Member

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    I don't have a mountain of experience in jumping bullets such as this, but I have loaded a couple of them. What I have found to improve accuracy in them is to change powder. For instance, my Rem 600 chambered in 6mmRem wouldn't shoot better than 2+" with IMR4064 when the bullets were seated to mag length but when I switched to H4895 the groups tightened up to 5/8", which is the same as the 4064 load with the bullets near touching the lands. I don't really understand why the propellent makes a difference but it sure does. I had a 264Win with this same problem but don't recall the details as I don't have the rifle anymore.
     
  6. Long Trang

    Long Trang Active Member

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    Use a process of elimination. If you want to know if it's because of a 40-70 thou jump, roll some rounds longer for a much smaller jump and hand chamber each one to test your theory.
     
  7. BigSkyGP

    BigSkyGP Well-Known Member

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    Sounds like you already have some great advice. pick a couple, and try them. Be sure to let us know how it all turns out!
     
  8. bowhunter42

    bowhunter42 Well-Known Member

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    I usually measure my chamber length and then my mag length to see what kinda jump im looking at. I then load to 5 thousadth's off the mag length and load 6 rounds, then load 6 more 40 thou off that and 6 more 40 thou off that down to around saami coal. I usually get about 4 groups of six rounds. one of these groups always shoot alot better than the others. I then use that as my starting length to develop a load for that rifle. I have found that something as simple as changing a primer can effect the grouping of a load. In my 300 win I found a load that shoot really well but my ES was up in the 50's I changed the primer from cci to federal and my Es dropped into single didgits but my groups opened way up. I changed to win primers with the same result. back to CCI primers and I increased the powder charge by .5 grains and both my group size and ES tighten back up. ES down to 11fps and Groups down to 1/2 inch. I am shooting Berger's out of it and long range performance is outstanding.
     
  9. tim jurczak

    tim jurczak Well-Known Member

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    Here is the latest. I went to the range with some 129 gr interbonds loaded at mag length. I did not even bother to measure jump this time as it has to be at least 50'thou. First I started working up with WC872 and as usual 1 1/2 groups. I brought my chrono along this time and realized I was getting ES around 75fps. Upper loads hovered around 3500 fps. Then I cleaned the bore and tried IMR 7828. First two groups measured 3/8" and 1/2"! Hurrah! Moved up anouther grain pressures were too high and velocity had peaked. Also groups got larger. ES with 7828 were around 40, and top velo was 3455 fps. I guess the moral of the story is what?
    I have been pondering every responds I have received and plan to try some barnes bullets. I have already switched primers and am going to see how it shoots single shot. Thanks, tim