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Help...Rifle won't group!!

11,385 Views | 73 Replies | Last: 4 yr ago by cupofjoe04
agingcowboy
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AG
Cooper Firearms
300 Win Mag
200 gr ELD-X

Avg velocity is 2945 FPS

I have shot this rifle at 1000 yds and more in the past and it's been consistent. Have killed elk in the 400 yard range.

I haven't changed anything on the rifle, but I haven't shot it much since moving back to TX. The last time I shot was about a year ago at the 1000 yd range at Best of the West, but they've been shut down so I've been trying to find a new longer range place to shoot.

I finally got out today at a new place in Marble Falls. Great place. To "qualify" for the longer range (up to 600 yds) you have to shoot a 1" 3 shot group at 100 yds. This rifle is zeroed at 200 and I've never actually shot it at 100 but I figured it wouldn't matter since they only care about the group. Long story short, I could not get this thing to group within an inch. The RSO said that this problem isn't uncommon in magnum cartridges because they're built to perform at long distances. Is this true? Surely this rifle should shoot 1" groups at 100 yds. I'm not a great shot or anything but I was shooting from a bench rest with bags and whatnot. Felt good and plenty steady. Anyone have thoughts/experience with this? I couldn't shoot it at longer distances to confirm since I failed the qualification (so humiliating!)

Please someone talk some sense to me before I start tearing this rifle apart and remounting my scope and stuff.

I guess the upside is I found a nice place to shoot. I have a membership now too which is good since I clearly need the practice. I guess I can just take my 6.5 cm out there and get qualified then shoot my 300 and double check it.
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BCStalk
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I would start with a different box of ammo and check the muzzle for any damage. Also any chance that your scope is loose?
agingcowboy
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AG
There's a chance. That actually happened once before, right after I first got it. I'll re-torque everything tonight and make sure.
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AggiePetro07
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Actions Screws
Rings/Base Screws
Damage to crown of muzzle
Scope went tits up

That's where I'd start. Most likely rings/base screws coming loose.

GSS
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What groups were you previously getting at the various other distances?
NRA Life
TSRA Life
BCStalk
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I've started using purple loctite on most screws. Don't know if that's frowned on though.
agingcowboy
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I haven't shot a lot of paper, but I found a few groups that I took pics of on my phone. One at 200 and one at 500 yds. 200 yd group was right at 2" and the 500 yard group sub MOA. That was 4-5 years ago though.
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Trigger06
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Groups can open up when the bore gets dirty. Give it a good cleaning.
slammerag
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Check crown, bases and rings. Cleaning is very subjective - Kreiger and bartlein barrels have interesting reads on cleaning
agingcowboy
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The scope is a NightForce so hopefully it's not that. I'll check the rest as you mentioned.
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CharlieBrown17
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Trigger06 said:

Groups can open up when the bore gets dirty. Give it a good cleaning.


Or conversely, if too clean go ahead and get it dirty
agingcowboy
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Well...shoot. I re-torqued everything. Action, base, rings. Nothing was loose though. I was hoping it was this. The muzzle looks normal. I have a brake on it but that's always been there. No damage or anything that I can see. Cleaned it but it wasn't particularly dirty. Guess I'll try to get it out again next week and see if anything has changed with what I've done so far. My elk hunt isn't until November so I have time to get it sorted. Hope i don't have to take it somewhere to get looked at but that's probably my next step.
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cupofjoe04
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+1 on the cleaning and then 2 fouling shots. Been though this with a .300 Win Mag before. After years of faithful service and meticulous care (so I thought), it inexplicably opened up. I drove myself crazy diagnosing everything possible.

Finally took it to the guy who made it- he said it had a bad buildup of copper fouling. He cleaned it, then I shot it back in and it's grouping just like it always has. A lot to learn about properly cleaning guns, and removing all the buildup periodically.
agingcowboy
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Ugh...just googled up a couple of articles about copper fouling and how to clean it. Sounds like a pain, but I may have to try.
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cupofjoe04
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agingcowboy said:

Ugh...just googled up a couple of articles about copper fouling and how to clean it. Sounds like a pain, but I may have to try.


It's worth trying now. This all happened to me 2 weeks before my antelope hunt last year. I ended up having to borrow a gun from my Dad for the hunt.

Your story just sounds so much like mine. But- the good news is noting was wrong. Just got it cleaned out, fired 2-3 fouling shots, and now it's back to turning dimes into donuts again.
Oso96
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AG
How many rounds have you put through that barrel? Is there a chance you have "shot out the barrel"?
agingcowboy
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200 grains at 2950 is fairly hot, but I think I've only got 300-400 rounds through it. I would think it would take more than that to wear the barrel out...?
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Oso96
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You should be good then on the barrel. When you talked about shooting at long range, I didn't know if you shot more than 3000 rounds through that barrel.
Log
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See if they'll let you try a 200 yd group. Sometimes bullets are erratic at 100 but have stabilized at 200.
C Loves L
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Trigger06 said:

Groups can open up when the bore gets dirty. Give it a good cleaning.


I was going to ask how dirty is this rifle?

I also suggest zeroing all of your rifles at 100 yards regardless
C Loves L
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agingcowboy said:

200 grains at 2950 is fairly hot, but I think I've only got 300-400 rounds through it. I would think it would take more than that to wear the barrel out...?


You're correct. That barrel theoretically should be just fine
C Loves L
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agingcowboy said:

Ugh...just googled up a couple of articles about copper fouling and how to clean it. Sounds like a pain, but I may have to try.


Give the barrel, bolt, chamber, and firing pin a good cleaning. I top mine off with Spartan accuracy oil after I've cleaned them up.

Good luck
dr_boogs
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What copper solvent did you use? I don't spend enough time rifle shooting to get copper build up frequently. I used a liquid based solvent last time. Put it in, let it soak per instructions, cleaned as directed.

Worked well but then I recently saw a paste product that claimed to work better. But I have also heard you have to be careful w copper solvents or you'll damage the barrel. Would appreciate your thoughts or anyone else w copper solvent experience.
91AggieLawyer
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giddings_ag_06
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Buy a new gun.
Old Sarge
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Make sure of proper stock to mechanism/chamber screw torque. It plagued me until I found this issue, unbeknownst.

Once corrected, no more issues.
daryl gersch
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I have a 1976 Sako 300 mag with a longer barrel than most. It's killed just about everything it was shoot at. From elk to deer to hogs to coyote. At long range. But after 30 plus years I couldn't zero my shots. Now I have shot a lot of rounds thru it, and someone told me to really clean the barrel. And I found out as long as barrel is clean I started getting great groups. But I had to clean the barrel after every shooting session. But it is now shooting like it always had. That is what helped me. Even if I shot one time, I would clean it for the next time. My 300 is the best rifle I have had or shot and doesn't kick for some reason. Compared to other 300 mags. Just my 2 cents.
cupofjoe04
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dr_boogs said:

What copper solvent did you use? I don't spend enough time rifle shooting to get copper build up frequently. I used a liquid based solvent last time. Put it in, let it soak per instructions, cleaned as directed.

Worked well but then I recently saw a paste product that claimed to work better. But I have also heard you have to be careful w copper solvents or you'll damage the barrel. Would appreciate your thoughts or anyone else w copper solvent experience.

***I am by no means an expert. There are FAR more qualified people on this board, and you should take their advice over mine. I just offer what little I have learned***

I had always used whatever solvent the local store carried- such as Hoppe's #9. I just thought I was getting that gun clean. After taking it back to the custom shop (after 22 years of use, but not many rounds per year) I learned differently.

They used Montana Extreme Copper Killer and showed me what was really in the barrel. I have since used it on 2 other rifles I have, and it works well. Just follow their directions closely. I certainly don't do this all the time, as it is hard on barrels.

I now use Butch's Bore Shine as my normal solvent. It seems to be better for day to day cleaning, and also helps remove a copper as you go (thus preventing the accuracy robbing build up). Im sure there are better options out there, but this seems to be working better than what I was using.

I will also add- I notice a significant difference in rifles that I have broken in the barrel properly vs ones not. A meticulous break in gives a proper surface that helps a barrel not build up.
sunchaser
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I like to use a caliber specific bore guide. "I believe" this guide is a one man shop or was when I bought what I needed years ago....very simple and helpful.

I think every one should break in a new rifle barrel at least once. Clean, fire, clean, fire etc and then all of a sudden feel how the push rod resistance is gone.

https://www.6mmbr.com/catalog/item/1433308/954882.htm
skelso
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Sounds like you are headed down the right path. When folks bring me guns that all of the sudden have precision issues, I first check for loose screws, check the crown, then go straight to cleaning. Especially if the gun has sat for an extended time.

Gun powder residue is corrosive. If you dont get it all out and let a gun sit a while, it will cause micro pitting that is guaranteed to give you precision issues. I clean with a quality copper solvent, then follow with a bore polish, then cleaning solvent. It's a slow boring process, but it generally tightens them up.

As Dr. Boogs said, be careful with copper solvent. Dont let it sit in a barrel too long because it can start eating molecules in the metal. Always follow copper solvent with a regular solvent or oil to flush the barrel.
Ark03
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It could also be the scope. You may try swapping it out with another to see what happens.
agingcowboy
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Thanks for all the advice. I didn't really know much about the copper build up issue. I've always just ran a patch through with solvent until it's clean. I've ordered some stronger bore cleaner and will give that a try. If that doesn't improve the issue I'll probably have to turn my attention to the scope itself. After that I'll have to take it to a professional. After that I'll try to sell it on here and hope this thread is buried far enough down that no one remembers it.
No material on this site is intended to be a substitute for professional medical advice, diagnosis or treatment. See full Medical Disclaimer.
Gunny456
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I have read your post and many of the replies. Lots of good advice given from all for sure. Most importantly checking all mounts and action screws for proper torque of tightness. Second would be the thorough cleaning to remove possibility of copper fouling.
Did you ever group your rifle at 100 yards or try to find the best grouping factory load for it?
Factory ammo can be very inconsistent from lot to lot. Cartridge Overall Length (COAL) is often changed per SAMI specs lot to lot because it has to work in all rifles under SAMI standards. The other culprit is bullet concentricity in any factory round and is oftentimes very inconsistent.
Don't worry about velocity and concentrate on finding an accurate factory round that fits your rifle or handload for it.
Accurate shot placement is much more important than bullet velocity/ weight.
Thirdly try a different scope if you eliminated all the other culprits.
Typically loose mounts or a bad scope will group a couple of rounds then throw one out.
agingcowboy
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Thanks Gunny. Some good advice here. I bought this rig with the intent to shoot far. I zeroed it at 200 and based everything off of that zero. Never shot at 100 yards prior to yesterday. I went through several factory loads and felt the best about his one as far as consistency. I'll try working through the list of likely culprits. I still hope it's not the optic but I am worried because the pattern you describe of 2 shots grouping and the 3rd a flyer is what was happening. Maybe my re-torquing did some good, although i didn't notice anything that seemed loose when I did it. I'll try it out at the range again next week.
No material on this site is intended to be a substitute for professional medical advice, diagnosis or treatment. See full Medical Disclaimer.
schmellba99
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agingcowboy said:

200 grains at 2950 is fairly hot, but I think I've only got 300-400 rounds through it. I would think it would take more than that to wear the barrel out...?
Your barrel isn't shot out by any stretch.

But at that number, you can start getting some changes in the throat via throat erosion in a .300 win mag - that can definitely change how a gun shoots because the distance from the ogive to the lands is increasing. Some bullets like a jump, some like almost no jump. May be worth looking into in addition to copper fouling.
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