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I was shooting my 7RM M77 tang safety yesterday and got a single flyer every time when the barrel cooled down and from the initial cold bore shot. What the group basically looks like is a flyer about 1" to the left then a seven shot group that is about .8" outside to outside. After letting the barrel cool down for an hour and a half I fired another round and it went into the same hole 1" left where the first cold bore shot hit the target. Next shot went into the 7 shot group again. Same thing happend again with the next cold bore shot.
The barrel is 100% floated and action bedded. I am not an expert and would appreciate any info, as some might be more familiar with this issue?
Thanks
Pieter
Last edited by m77; 03/29/15.
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I had a ruger 30-06 that did this as well. Since you already have the barrel free floated, and the action bedded, you can likely eliminate those issues, provided the bedding was done correctly. I am not an expert, but it sounds like you have a harmonics problem with the barrel. The harmonics on the cold barrel are diffenrent than when it has been shot and is warm. A couple of suggestions: if you reload, and are not at a max load, try going up .5 or 1.0 grains of powder. Also, if possible try and extend the bullet out in the case about .001. This may give you enough change in harmonics to "fix" the problem. I have a custom bartlein barrel and after 250 rds I developed a slight impact change on my first round. (about .5inches at 200yds.) I did both of the above, and eliminated the problem.Not sure why it took that many rnds to develop. I have also heard of people using those rubber dampners that fit over the barrel to change the harmonics. It may be a gimmick, but then again it may work. If your barrel is long enough, say 24-26" you could also have a gunsmith cut off 1" and recrown. This may fix the harmonics issue as well. On my ruger, I tried everything but cutting the barrel, and never did fix the problem. I sold the rifle. If these things don't work, either sell the rifle, or rebarrel it,because you will never have confidence in the thing. Good luck!
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I have also heard of people using those rubber dampners that fit over the barrel to change the harmonics. It may be a gimmick, They work !
"Only Christ is the fullness of God's revelation." Everyday Hunter
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limbsaver makes the dampners. I have an old one I used a few years ago just to try it,but the rifle I used it on already shot well, so I didn't see a big improvement. On the 30-06 ruger I described above, it helped it, but the first shot was still off.
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Luck....is the residue of design...
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Have you cleaned the barrel? I have not experienced it but have heard of copper building up in the barrel which deforms the bullet until it is heated and softened by one or two shots.
I have also read of people either fixing or at least reducing how much the bullet is out by using the Tubbs bore lapping kit.
Dave.
Those who are always shooting off at the mouth usually aren't shooting straight. Build a man a fire and he’ll be warm for a day. Set a man on fire and he’ll be warm for the rest of his life. www.wvcdl.org
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Thanks for the info guys. I have read that shot out barrels are prone to this problem but this barrel does not have many shots through it. I am going to clean the rifle to bare metal and see if it makes a difference. I hope I can get a solution without a dampener as they do spoil the looks of a rifle a bit :), but I will check if that might be the solution.
I am hoping that I can get away without replacing the barrel!
Thanks again.
Pieter
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One easy thing you can try is putting some upward pressure on the barrel. Some Rugers like this I guess, I've only got one but I floated the barrel and had to reinstall a pressure point in the fore end. Loosen the action screws and slip in a piece of plastic like a chunk of credit card and slide in under the end of your barrel so it fits firmly between barrel and stock when you tighten the action screws back down. This might improve things and is easy to do, and undo.
"I was born in the log cabin I helped my grandfather build"
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I have also heard of people using those rubber dampners that fit over the barrel to change the harmonics. It may be a gimmick, They work ! They might work fine. But, I'd re-barrel or re-rifle before I'd pack a gun around with one of those things on it.
"I never thought I'd live to see the day that a U.S. president would raise an army to invade his own country." Robert E. Lee
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Campfire Kahuna
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folks get to worried about cosmetics, when they should be worried about accuracy.
the rifle or gun is simply a tool to get a job done. Don't much care what it takes to get em to shoot or how they look, as long as they do the job.
We can keep Larry Root and all his idiotic blabber and user names on here, but we can't get Ralph back..... Whiskey Tango Foxtrot, over....
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Originally Posted By Ringman Quote: I have also heard of people using those rubber dampners that fit over the barrel to change the harmonics. It may be a gimmick,
They work!
They might work fine. But, I'd re-barrel or re-rifle before I'd pack a gun around with one of those things on it. I enjoy testing things. I tried it on at least three rifles. Like I said, they work.
"Only Christ is the fullness of God's revelation." Everyday Hunter
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So does silicone in the barrel channel, and you dont have to look at the cock ring hanging on the barrel.
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Though I'm not sure I would resort to one, my pard in ID has one on his go-to rifle. Not many here would scoff at his, mostly, DIY trophies. He's far from a rifle loony, but about as loony as it gets for putting critters down. That said, everytime I hunt with him I giggle inside thinking what the folks here would think of his setup, then I get tired helping him pack something out...
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Just an update. I tightened the rear action screw a little extra and the first shot was a little closer to the following shots when I fired the rifle over the weekend. It also impacted slightly lower. I am thinking that the bedding might not be 100% stress free. It still shoots just around 1" at 100m with the cold bore shot, but I would prefer that first shot to be closer to the 'main' group to the right. I also removed quite a bit of carbon from the barrel (more than I expected and it is still not 100% clean), but I do not know whether too much carbon would have an impact on a cold bore shot?
I think I will check the stress on the action and maybe target the carbon with some iosso paste and see if it settles down.
I will look at dampening the barrel but first I want to eliminate all other possible problems.
I must say, I am amazed that this rifle (apart from the cold bore shot) can shoot a 10 shot group at around .8" even when the barrel starts getting pretty hot.
Thanks again for the info.
Pieter
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