Shrink group size...some advice or help.

Discussion in 'Long Range Hunting & Shooting' started by shooters, Oct 17, 2019.


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  1. shooters

    shooters Well-Known Member

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    Feb 28, 2007
    Some info that may help....
    Looking for advice on where to go from here. This is where I get lost. Powder type? Bullet Depth? Powder Grain change? Etc? Need some help on what to do next to tighten this group up.

    Clean Bore. Been bore scoped by pro
    Barrel only has 38 rounds through it.

    300 RUM
    1/10 twist
    26” Proof Barrel
    Defiance GA Hunter Action.
    MCMillian Stock
    Trigger Tech set at 1.5lbs

    208 ELDM
    215M Primer
    Reloaded 33 Powder
    Nosler Custom brass
    Loaded round 339 at neck
    Redding FL 337 Bushing
    3.091 at Ogive
    .003 off lands

    96g Reloader 33 looked like I was shooting a scatter gun. Horrible. Don’t see how 1
    Grain of powder made that big of difference.
    95g instantly shrunk to about an inch group.
    94.5g was a about same. No change. So based off this pic, I’m not sure what to do next or where to go with seating or charge and so on. I’m basically at mag length too.
    That’s a 5 shot group.
     

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    Last edited: Oct 20, 2019
  2. dfanonymous

    dfanonymous Well-Known Member

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    With ELDs in general you’ll want to play with seating depth. I don’t have a RUM anymore but with my other 30 cals I’ve gotten a better groups with mag length depths or sometimes simulating factory ammo seating depths. I’m sure others experience will vary.
    Next, I think annealing brass and getting a consistent neck tension is more important then a lot of the other complicating things people do like sorting brass and what not.
     
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  3. Wolf76

    Wolf76 Well-Known Member

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    A little of topic, but shooting a 215-230 Berger has always shrunk my group size. Put the 215 about 25-40 thousands off and see what happens to your groups. I won't use eldx bullets because of terrible BTO and weight variances. No experience with the M line.
    Your experience its also why I determine seating depth first.
     
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  4. L.Sherm

    L.Sherm Well-Known Member LRH Team Member

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    Try a CCI 250 it's amazing what just a primer change will do. Looks like to me you have some vertical going on.
    If that doesnt work I would switch powders, 33 is temp sensitive I have found.
     
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  5. Orange Dust

    Orange Dust Well-Known Member

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    I have always had the best luck with retumbo in my rum. 215m primers. Hard to find right now though. Mine will shoot under an inch with every bullet ive tried im mine with this powder. Try some ADG brass. I swear it is good as Lapua. The RUM is one of the easier big cartridges to find a load for.
     
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  6. Creedmoor shooter

    Creedmoor shooter Well-Known Member

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    I would start working your seating depth if you haven't already. My rifles have never been very picky where the eld is seated but yours might. If I'm reading it right your .003 off the lands. I'd start working back in .010-.020 increments until you find where it seems to like it then fine tune by going .005 on either side of the depth you found to work best and see if that tightens it up any.

    If that doesn't work and it still shoots like that then I'd look into a different bullet. No sense in banging your head off the wall over bullet that your barrel just doesnt like.
     
  7. Orange Dust

    Orange Dust Well-Known Member

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    Also, try a 215 hybrid. Ill bet it will shoot with Retumbo. I tried Re33 in my 28 nosler and hate everything about it. Ended up with 8133 and its ok but not great. Everyone says use 570 but, like Retumbo, about impossible to find. Havent tried 8133 in my rum but would if i couldnt find retumbo.
     
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  8. yoteslayer

    yoteslayer Well-Known Member

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    Are you using Vergin brass or fired you will get better groups with fire formed brass and do you know how much you are bumping shoulder back if you’re target shooting 1-2 thousands from fired case if hunting probably like 2-3 thou and when seating the bullet do they all feel the same if some feel tighter then set them aside when you reload good luck
     
  9. Orange Dust

    Orange Dust Well-Known Member

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    One orher thing. I've bought some nosler brass that i swear the necks were harder than the heads. Anneal the necks and skim turn them. The necks are very inconsistent in this stuff. I quit buying it.
     
  10. yobuck

    yobuck Well-Known Member

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    I’d shoot it at 400 yds and see how it performs there.
    I’d also install a break if it doesn’t already have one.
    100 YD groups for long range hunting guns don’t mean much.
     
    Mram10us, L.Sherm and shooters like this.
  11. shooters

    shooters Well-Known Member

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    It has a break and I’ll shoot out to a 700 today just to see.

    I’ve loaded....
    6 rounds of exact same load that I’ve already shot (.003 off lands with 94.5 Reloder 33. The picture I posted.

    6 rounds of same load but now .0010 deeper so .0013 off lands

    6 rounds of same load but now with 91.5g retumbo at .003 off lands

    6 rounds of same load 92.5g retumbo at 92.5g.

    This is my 6th 300 Rum built. I’ve never had an issue with any of them when shooting Retumbo and have only used Reloader 33 in the last two with excellent results. I’ve also only ever shot 200 Accubonds and 200 ELDX and all have been 1/2” group. I’m just really wanting these 208’s to work. I’ll post up pics of each group today. Thanks!
     
  12. LongBomber

    LongBomber Well-Known Member

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    #1 I would sort bullets by bearing surface length, any of the eld’s I have had were not very consistent and giving me results that were tough to duplicate.
    Then I would take that 95gr powder charge and run a seating depth test. Normally I would do it in .010” steps but you could do it berger style with larger steps.
     
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  13. SealTeam4

    SealTeam4 Well-Known Member

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    Did the rifle shoot well at first and then degrade? Or is this how it has shot since the first round?

    Joe S.
     
  14. Canhunter35

    Canhunter35 Well-Known Member

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    I’ve had exceptional accuracy out of 208s, but my proof will not shoot 180eldms. Ive done everything. It’ll shoot smk and Berger’s decently