300 rum accuracy questions

Discussion in 'Reloading' started by Donavonc2000, Sep 18, 2011.

  1. Donavonc2000

    Donavonc2000 Member

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    Sep 18, 2011
    Hello, looking for any advice regarding my christensen arms 300rum. I have a consistent accuracy issue that is driving me nuts. Through out load development I have been experiencing a group pattern where 2 are sub 1/2 moa and the third is 1moa or more. I sent the the gun back and had a select match barrel installed and have experienced the same pattern. The best load in the old barrel was 210 vld 92.5 h1000 3.685 o.a.l. The new barrel likes 92.5 retumbo and a 200 gr accubond or 210 vld 3.665 and 3.685. I have achieved .490 .450 respectively but it will only shoot one out four groups. The others display the same old pattern of basically touching and a third randomly positioned somewhere out at MOA or more. There is no consistency what shot or where out side it will be. The velocity spread is low (15fps). I guess I am left scratchig my head and am quite frustrated at this point. If any one has had similar issues or I am missing something please feel free to put in 2 cents. Thanks so much for any help.
     
  2. Footsore

    Footsore Well-Known Member

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    Sep 28, 2010
    That barrel may be getting hot and causing the third shot to shoot off a bit. How long are you waiting between shots? Is it a carbon wrapped barrel?
    The is quite a bit of heat generated with that cartridge.
     

  3. Donavonc2000

    Donavonc2000 Member

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    Sep 18, 2011
    Hello, Yes it is a carbon wrap barrel, And it will do it hot and cold bore with ample cool down. In fact the times it actually grouped the gun was quite warm. What drives me nuts is that two shot are touching or almost touching consistently. It displays same pattern at 200 yards and It will do this with basically any bullet. 220smks 200 accubonds 210 vlds 180 accubonds 185 VLDs. The barrel is floated but there is no pillars in the carbon fiber stock. I am wondering if that has any thing to do with it. Any ways, thanks in advance for the input. This gun may be heading back the maker permanently.
     
  4. BlackStreak

    BlackStreak Active Member

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    Apr 11, 2011
    I just got done with such a problem. All the powders I expected to do well such as Re 25, Retumbo, H 1000 didn't give me good groups at all. I played with bullet seating in each load also along with working my loads up till I seen pressure signs on my primers and case head. Found my reload in both H 4831 and IMR 4831. I shoot 5 shot groups however, I put the gun back in the truck in the airconditioning to cool the barrel off after the 3rd shot at 200 yards my gun in shooting 1.2 inch groups. Virtualy 1/2 MOA and both brands of powder did this with 5 shot groups. None of the other powders would do this through my rifle which kinda stunned me. I shoot 210 VLDs with them pushed pretty far into the lands. Back off the lands and the VLDs typicaly open up.
    Could be internaly in your scope. Shoot 5 shot groups. If u get a cluster of 3 and a cluster of two then ur scope might not be up to pare. There are different ways to trouble shoot this. Also, be sure u have the paralax adjusted out of the scope. I'm sure u have a steady rest to eliminate as much human mistake as possible during load development. Also durring bullet seating u want to make sure your not putting so much pressure onto the bullet when seating it that ur not compressing the case neck so hard onto the bullet that your squizing the bullet to hard. Good luck to you!
     
  5. knc1105

    knc1105 Well-Known Member

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    Feb 22, 2010
    Mine liked Retumbo and 200 gr Accubonds. I had my bullets Boran Nitride coated by Superior Systems Systems.com I was worried about barrel heat and wear and throat erosion. The Boran on my other rifles has extended barrel life a bunch. In fact I have not replaced a barrel since I started shooting Boran on all my rifle bullets. It does keep barrel temp way down. My 300 RUM is a 700 Police which is a heavy (.920) barrel but my custom 338 RUM is a #5 profile Lilji barrel. I need to take a infrared temp gun, but to the touch my 338 is approx. the same same temp after 5-slow fire shoots with Boran than it is after 2-naked bullets. Superior is so busy moly coating bullets for Sierra that they have quit coating for the public but they offer a complete kit with their propritary Boran mix and you can do it yourself in a large tumbler. It's more convienent and is alot cheaper, you don't have to wait for service, and you save shipping bothways.
     
  6. Donavonc2000

    Donavonc2000 Member

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    Sep 18, 2011
    Hello Thanks for the input fellas. I have not tried 4831 in any of the loads. That may be next, what charge is an appropriate starting point. I have changed the glass and mounts for the third time today and made absolutely sure there was no parrallax in the scope and shot a cold 3 shot group with the same load that achived the .450 group and it shot 1.3. I shot a warm group with 185 vlds and it shot 1'' with two touching and a third randomly out. I have studied all of the groups and the overwhelmingly obvious connection is the 2 shots with a third out. I shot a five shot at 300 with 1.3 moa results. So I guess I am back to sqaure one. One thing I have noticed is that the necks of the spent round have alot of carbon on the them all the way back the the shoulder. I am wondering if that indicates anything. I guess I should try to just get refund and get a Bettin or a Jense or some other custom packable 1/2 MOA .308. Thanks again for the help
     
  7. pdawg.shooter

    pdawg.shooter Member

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    Feb 10, 2009
    My 300 is an old cheep Savage 116. Stainless, laminate stock, and pillar bedding from the factory....but... the recoil lug did not contact the stock. A bit of accraglass cured this problem. Reloader 25 and 200gr. TSXs will shoot into 1.25 @ 200.