300 RUM Sendero very inconsistent!

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by SAPPER26, Nov 7, 2011.

  1. SAPPER26

    SAPPER26 Well-Known Member

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    I have a 300 RUM M700 Sendero I have been having issues with. I have had 4 different bullets with loads that would give me at least .5 moa 3 shot groups.

    208 AMAX, 94 gr Retumo
    225 gr hornady, 87 gr Retumbo
    200 gr Accubond, 93.5 gr Retumbo
    180 gr TTSX, 95 gr Retumbo

    Each load would shoot well, and then for no apparent reason, it would not group any more. I would start load development again. It was originally unbraked and the Amaxs worked well. After finally deciding to quit punishing myself, I had a break installed ( Holland QD) by a local gunsmith. It now has become erratic. One day it will give me a stellar group, then the next, the very same load will open up to 4+ moa. I skim bedded it to see if it would improve accuracy, but it is still giving me inconsistent groups. It would throw down a 1.25" group @ 300yds consistently, and then the next day with the same exact load, gives me 8+ inch groups. Same conditions, same set up. The crown on it is very rough where the gunsmith milled it, but looks good by the rifling. It has approximately 250 rounds through it. I torqued the action, even over torqued when it goes erratic to see if it cures it. No dice.

    I was going to use it on a elk hunt this weekend, but don't feel confident with it after all this. I don't want to go under gunned, but I'll be taking my tried and true 308 that will always give me .5 MOA. I regress. Would it be burned out? The scope is a MK4 4.5-14. Is the scope the issue? I'll swap out with a night force when I get back from my elk hunt, to see if it's the issue. I'm thinking of taking it to G A Precision since Kirby is a few states away, to see if they find anything out of the ordinary.

    I would take the 338 lapua I just received from kirby allen a couple months ago on the elk hunt, but I have more invested in it than the airlines would cover if it got "lost". By the way, it's shooting well under .5 moa, but thats another story. Thanks for any help.
     
  2. elkaholic

    elkaholic Well-Known Member

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    At first glance, it would sound like a problem that occured from the brake being installed i.e. maybe crown? If that were the case, however; It shouldn't group well one day and not the next. It could be a number of different things: Bedding problem....was the stock removed during the time the smith had it or after you got it back? If so, I would start by making sure your magazine is not binding the action. This is a VERY common occurence. Whatever is wrong, it sounds like something is moving. Have you checked your scope mounts on both the base mounts and rings? What kind of scope do you have? After you have checked everything else, you might mount a different scope. It could be internal scope problems. Normally I would ask about shooting conditions or shooter error but it seems like the groups are far to erratic for that. Good luck and let us know what you find.......Rich
     

  3. SAPPER26

    SAPPER26 Well-Known Member

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    Elkaholic,

    The stock was removed but always re torqued. I'm not sure what you mean by the magazine binding the action. Does this mean the box is pressing against the action and bottom metal? Scope is a Leupold MK4 4.5-14. MK4 rings and base. Base was JB welded to receiver since there was air gaps when base was on receiver. Everything is tight. If I don't take it to a gunsmith on my way to the airport Thursday, I'll put a NF on it when I get back to see if that's the issue. Does this sound like a scope issue? the erratic groups are usually 2 low next to each other and one high left, or two next to each other and one far left, same plane. 5 shot groups are spread all about. Thanks for your help.
     
  4. elkaholic

    elkaholic Well-Known Member

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    The box magazines are rather easy to not get fitted correctly into the bottom of the receiver on a 700 Rem. There is a shallow slot in the bottom of the receiver that it "friction fits" into and sometime takes some doing. Be careful when you place the barreled action back into the stock and make sure the box remains completly bottomed in the slot. When it is assembled properly, the bottom metal should not be pressing against the box and the box should not be cocked in the stock cutout. This would be my first check as this can DEFINITELY cause the condition that you describe....Rich
     
  5. ICANHITHIMMAN

    ICANHITHIMMAN Well-Known Member

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    I would cut your losses now send it to Kevin Cram spend your 200 bucks and have him go over it. I didnt read past rough looking crown, that combind with your fustration is enough to tell me you need to start over.

    Could very well be the scope or the way you mounted it. Loose base screws maybe.
     
  6. SAPPER26

    SAPPER26 Well-Known Member

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    Base screws are solid. Scope rings checked out. Could be internals. The magazine box was installed properly. Could a barrel be burned out in 250 rds? I've never loaded it too hot. Contacted GA Precision in Kansas City and they're willing to take a look at it. If they have to do too much to it, I think I'll just bite the bullet and have them true the action and re barrel it since spending more on this rifle with a usable life of around 700 rds wouldn't feel right. Question then would be; stay with the RUM, or something different? Would the bolt face for the RUM work for a plain 300 WM? Thanks for all the help.
     
  7. elkaholic

    elkaholic Well-Known Member

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    Not likely a barrel would burn out in 250 rounds but could be damaged in other ways. A RUM bolt face is too large for a WM. Taking it to a smith is not a bad idea. I've had three RUM's and have now gone with less capacity because I shoot a lot. The RUM's don't last......Rich
     
  8. MTBULLET

    MTBULLET Well-Known Member

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    for what it's worth, my first 300RUM, a rem. 700, had exactly 272 rounds thru it when it toasted the bbl. 2nd. bbl, PAC-NOR, went to 867 rounds before it lost accuracy.
     
  9. MTBULLET

    MTBULLET Well-Known Member

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    also, the 300 rum base dia. is .534, 300WM .532. Ire bbl'd. one of my 300rums to 300 win mag with no problem.
     
  10. elkaholic

    elkaholic Well-Known Member

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    You are correct! I gave him bad info as I forgot that the RUM has a rebated rim. The body is .550" but the rim is .534. My Bad!.........Rich
     
  11. Hired Gun

    Hired Gun Well-Known Member

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    I install a lot of brakes on 300 RUM's and I have seen this before. What size thread did your smith use on the brake? If it's a 5/8" or smaller overtightening the brake will put a constriction in your barrel right under the threads. The verify either loosen the brake or remove it entirely and test. If the accuracy returns then you can hand lap a bit off the back of your brake and reinstall with less torque and still maintain the timing. It also may not be installed concentrically. If it's off center your groups will be all over the place.

    Your barrel should have lots of life left in it. To get max milage don't shoot it hot. 3 at a time is max before you let it cool. I have inspected them with only 60 rounds through them and they had 10 times more wear than my 700 round 300Wby has. When I told him that he said he was shooting 20 shot groups as he was getting frustrated with the accuracy and just kept shooting. With his new brake he has reported sub MOA accuracy and the recoil is down to 243 sporter levels.
     
  12. SAPPER26

    SAPPER26 Well-Known Member

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    Hired Gun,

    Pretty sure it's 5/8". When I got it from the smith, the holes on top of the brake didn't quite align vertically. I got a screw driver and tightened it a little to make it "fit" better. I thought this could be a problem, so when it was grouping poorly, I took the brake off to see. It still grouped poorly. I don't think it was an issue. It's at G A Precision right now. Should get back with me this week with a diagnosis. Thanks.
     
  13. SAPPER26

    SAPPER26 Well-Known Member

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    Got the rifle back. GA Precision said there could be a few issues causing the erratic groups. First was the bedding might be the issue. They saw that it might have a high spot. The other was that the bolt handle was contacting the stock. The smith at the shop said he saw this in many military rifles and it caused the same problem. They corrected that issue, I held off on the new bed job since I'd rather rebarrel it than pay to bed it and not be sure. I'll dremel out the old bedding and Devcon bed it myself this weekend. Hopefully this works. If not, I'll be getting a new barrel and most likely chamber it in 300 WM. Thanks for the help everyone.
     
  14. pyroducksx3

    pyroducksx3 Well-Known Member

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    I have rem 700 in 7 rem mag that does the same thing. So I'm doing the same thing, taking it to a smith having it blueprinted, custom barrel, new stock and bedding it. Smith will guarantee it will shoot 1\2 MOA problem should be over :)