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Thread: How much bullet bearing surface in the case mouth is needed?

  1. #1
    RHOTWING
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    How much bullet bearing surface in the case mouth is needed?


    I have just started loading for one of my rifles in 6.5x284. It is a Savage 116 FHVSS with a 24" BBl. I wanted to use some Berger VLD bullets, so I loaded some of their VLD Long Range BT Target bullets PN#26409, as I want to get out to 1000 yards. I used the Stoney Point OAL gauge to measure to the lands. I used Berger’s recommendation to find the best seating depth. They recommend starting at .010 off the lands, then .050 off, and .090 off and finally .130 off.

    Well with these bullets seating at .010 off I had approximately 1/32" of bullet bearing surface in the mouth of the case, even with .130 off that made it approximately 5/32" of bullet bearing surface in the mouth of the case. Out of the 72 rounds there were 24 three round groups. My chrony quit working after the fourth round so we were unable to record velocities.

    The accuracy was not what I was hoping for, I can shoot 1-MOA 75% of the time and my brother whom was helping shoot can get 1-MOA and better almost 100%, but he was having a bad day. We had approximately 80% of the groups under 1 MOA, but what I'm shooting for like most others is one ragged hole!

    Anyway we had very inconsistent grouping, so I couldn't get a read on what seating depth might be favorable. I did notice though that on the cases of the 18 rounds seated at .010 off the lands, there was carbon/smoke stains on the cases, so I think they need to be seated deeper.

    Has anyone else run into this issue with their Savage rifles in seating bullets .010 off or closer, and not having proper bearing surface of the bullet seated in the case mouth?
    It would be impossible with these bullets for me to seat a bullet jammed into the lands as there wouldn't be enough bullet bearing surface to work with.

    I guess with this gun I am going to have to find a load that will be happy with a considerable jump.

  2. #2
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    The carbon/smoke stains on the cases is usually a sign of low pressure. The case doesn't expand enough to provide a tight seal against the headspace point. Also, do you have a twist rate on the barrel that is acceptable for the VLD's? Most Savage factory rifles also have generous amounts of throat which in most cases makes it near impossible to seat near the lands. Sierra MK's do very well jumping to the lands normally.

  3. #3
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    I am not an expert on this, but the general rule of thumb is to have one bullet diameter of bearing surface in the case neck. In your case-.264". I have loaded cases with less, but the main thing is, you need enough bearing surface in the neck to provide adequate seal and ensure against excessive run out.

    With as much jump to the lands as you mentioned, I don't think you will be chasing the lands with that bullet, in that barrel;-((

    Good Luck-Good Shooting

  4. #4
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    Should've bought a creedmoor to shoot vlds. They are engineered to avoid that issue.

    Ideally you want the bullet diameter in seating depth. I would work at the saami length and see what you can come up with then tune from there.

  5. #5
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    I haven't been reloading for very long at all, but did you find a charge that the rifle likes prior to playing with seating depth? 72 rounds is a lot of components for determining a load. If you haven't determined a charge that provides the best accuracy yet try doing that first. Best to play with one item at a time to avoid trying to figure out which item it is that is causing the accuracy issue.

    Also as always make sure you have a solid shooting position with front and rear bags. Make sure you aren't using muscle support to get the rifle on target. As well as make sure the scope is mounted properly and all the other items that can be an issue with a rifle just from the factory.

  6. #6
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    Seat the bullets where they need to be and shoot it. If they dont shoot try different bullets. The world dosent really revolve around Berger.
    What options are there other than setting the barrel back and having it rechambered.

  7. #7
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    Amax would probably be a better option in this case.

  8. #8
    Basic Member Dennis's Avatar
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    I have had the best luck with VLD's .010 in the lands or a few thousandths more. I have shot several .001 4 shot groups with the Bergers. Also have the best luck with RL17!

    Dennis

  9. #9
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    You might try the 140grn Nosler Accubonds. They have a lot of copper in them, so they are longer than other bullets of the same weight. Also, they have a very blunt Ogive, relative to the Bergers, keeping them from going as far up into the throat. These two things together may help you get closer to the lands and have more bullet in the case neck.

    But, as mentioned above, you can't chase the lands with a particular bullet if the barrel won't allow it. But that's OK. I have a 30/06 that shoots very good groups with a .160" jump tp the lands. As already suggested, load those Bergers .264" into the case neck, and see how they shoot. You can always fine tune the load with the powder. Then you will at least know the best you can get out of the Bergers.

    Good Luck-Good Shooting.........Jim

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