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300 RUM Sendero very inconsistent!

 
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  #1  
Old 11-07-2011, 10:37 PM
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Location: Vass, NC
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300 RUM Sendero very inconsistent!

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.
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Old 11-07-2011, 11:15 PM
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Re: 300 RUM Sendero very inconsistent!

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
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Old 11-07-2011, 11:32 PM
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Re: 300 RUM Sendero very inconsistent!

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.
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Old 11-08-2011, 12:32 AM
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Re: 300 RUM Sendero very inconsistent!

Quote:
Originally Posted by SAPPER26 View Post
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.
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
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Old 11-08-2011, 08:35 AM
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Re: 300 RUM Sendero very inconsistent!

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.
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  #6  
Old 11-08-2011, 09:43 AM
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Re: 300 RUM Sendero very inconsistent!

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.
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  #7  
Old 11-08-2011, 10:19 AM
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Re: 300 RUM Sendero very inconsistent!

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
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