Uneven Rifling Wear or Bad Chambering?
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  1. #1
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    Default Uneven Rifling Wear or Bad Chambering?

    Hey all, I recently purchased a used Savage 12 chambered in 260 Remington. I have taken it to the range several times in an effort to get it grouping up. It has however been resisting my best efforts to get groups under 0.750". I suspected that the barrel on this unknown rifle was possibly to blame so I purchased some Cerrosafe and did a chamber cast of the chamber and about an inch of the throat and bore. After looking at the cast I am seeing that it appears as though the rifling is uneven in relation to the end of the chamber. I did my best to measure this with my little caliper and came up with the following measurements.

    0.192"
    0.178"
    0.164"
    0.149"
    0.221"
    0.209"

    It seems at though the rifling was either not cut correctly, the rifling wore unevenly, or I messed up or am misinterpreting the chamber cast. I did clean the bore thoroughly before doing the cast, but maybe some tough carbon or copper is stuck there. Anyone ever see anything like this before?
    20191003_144509.jpg20191003_144526.jpg20191003_144401.jpg20191003_144438.jpg20191003_144548.jpg

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    Nothing new with Savage, I have run into a few like that. Can't figger out how to duplicate it though

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    Looks like an off center cut chamber, and no they won’t shoot worth a damn.
    Mike Belm has a website that shows chamber casts with the same thing on tc encore barrels.
    Tc simply says they are “ in spec” and won’t replace them .
    Savage has a pretty good warranty dept, they may make it right.
    Otherwise your options are to set the barrel back , pre bore, and re cut the chamber or just replace the barrel with a quality prefit.

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    Your method of measuring can be the source of a lot of that discrepancy. I would probably set the casting on a a surface plate and use a height gauge to measure to the rifling. At the very least I would take measurements from the base of the casting up to the start of the rifling. Unfortunately even those methods will have some built in error to them as there is no solid point on the rifling to measure to, you have to eye it. The base of the casting could also be rounded or uneven.

    JMHO

    -Ron

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    This was a standard compliant about remington 700s......its obvious even when viewed with a cheap camera......However return the gun ,and you will get nowhere,if its shooting .75" groups......because this is well within the SAAMI spec for the caliber.......and also Savages guarantee of sub minute groups.....The effect is easy to reproduce,chamber with a single point tool in a CNC machine with the bore slightly off centre......the effect is obvious with as little as 002 runout.

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    two years back i bought a $1200 rem 700 in 300 wsm. first new cf rifle in over 20 years. got my bore cam the same day. never fired the rifle. off center chamber. several months of bs and it was replaced. i sold the new replacement without every looking at the bbl, and went back to building my own rifles.

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    I am puzzled when individuals feel that a lower mid-tier, mass-produced rifle that shoots 3/4 minute of angle is somehow defective.

    That's perfectly acceptable. Want 1/2 minute accuracy, buy an aftermarket barrel that's higher quality.

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    i think he is questioning the quality of the chambering vs wear.
    it is pretty clear it is a poor chambering job as it is not straight,
    in spite of shooting under 1 moa.
    poor quality is poor plain and simple

    Quote Originally Posted by tobnpr View Post
    I am puzzled when individuals feel that a lower mid-tier, mass-produced rifle that shoots 3/4 minute of angle is somehow defective.

    That's perfectly acceptable. Want 1/2 minute accuracy, buy an aftermarket barrel that's higher quality.

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    Could the barrel be the culprit? Maybe.

    When you start trying to get a gun to shoot under .75” there are lots of little things that could be affecting the accuracy. Some of them not entirely the guns fault.

    What is your shooting cadence?
    Is the barrel heating up and throwing shots?





    Check out my website!
    The Ballistic Assistant

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    That is a result of off-center chambering. When that 1.5 degree throat gets cut off-center, the change in freebore length can alter drastically from one side to the other. .75 MOA is reasonable performance if it is consistent. If you're chasing tighter groups and reloading isn't helping, have the action, lug, and bolt head trued and have a nut-less barrel installed.

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    sorry look at the chamber cast
    Quote Originally Posted by JayAndrew View Post
    Could the barrel be the culprit? Maybe.

    When you start trying to get a gun to shoot under .75” there are lots of little things that could be affecting the accuracy. Some of them not entirely the guns fault.

    What is your shooting cadence?
    Is the barrel heating up and throwing shots?





    Check out my website!
    The Ballistic Assistant

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    I did...Looks pretty bad to me and I am not saying that changing it out won’t reduce the group size, it just may not make as big of a difference as the OP is hoping.

    When you’re trying to get a production rifle to shoot from 3/4 to under 1/2 you usually have to do more then just swap a barrel.

    As a previous poster mentioned, blue print the receiver, square up the bolt face, and lap the locking lugs for a start...

    Then you have to look at how your conducting the accuracy test. I have seen shooting rests be responsible for throwing shots.





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    Default Someone once said

    that accuracy is all about bullets and barrels. (and I believe it)

    To have a chance at accuracy the bullet has to enter the bore straight. If the chamber is cut off axis and/or crooked then you are giving up much accuracy potential.
    Rifling cut unevenly will create imbalance in the best of bullets so there too it has limited accuracy potential.
    These conditions are observable and measurable. If present there is no way to compensate for this by changes in reloading or bench manners.

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    Guess that is why Kenny Jarrett rifles cost so much.
    .164 to .209 .. that is a lot of error.
    QT: [ a used Savage 12 chambered in 260 Remington.] who knows who did the job..perhaps made his own reamers and used a not mentionable lathe to run it.

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    Quote Originally Posted by akajun View Post
    Looks like an off center cut chamber, and no they won’t shoot worth a damn.
    Mike Belm has a website that shows chamber casts with the same thing on tc encore barrels.
    Tc simply says they are “ in spec” and won’t replace them .
    Savage has a pretty good warranty dept, they may make it right.
    Otherwise your options are to set the barrel back , pre bore, and re cut the chamber or just replace the barrel with a quality prefit.
    I looked up Mike Bellm and found that article on his website. Looks exactly like the chamber cast I have. It seems that the general consensus is the barrel was chambered off center.

    Quote Originally Posted by MetalCarnage View Post
    Your method of measuring can be the source of a lot of that discrepancy. I would probably set the casting on a a surface plate and use a height gauge to measure to the rifling. At the very least I would take measurements from the base of the casting up to the start of the rifling. Unfortunately even those methods will have some built in error to them as there is no solid point on the rifling to measure to, you have to eye it. The base of the casting could also be rounded or uneven.

    JMHO

    -Ron
    I would agree. Unfortunately I don't really know a better way to get more precise. The base of the cast is a big glob of overcasted material and the rifling start lines are open to interpretation. The inconsistency is visually obvious as you roll the casting on a table and my method of using the calipers was the quickest way to show the difference in pictures for the internet.

    Quote Originally Posted by tobnpr View Post
    I am puzzled when individuals feel that a lower mid-tier, mass-produced rifle that shoots 3/4 minute of angle is somehow defective.

    That's perfectly acceptable. Want 1/2 minute accuracy, buy an aftermarket barrel that's higher quality.
    I wouldn't say defective maybe just disappointing. The model 12 HS is supposed to be their target model. Many others that have these rifles are reporting sub 1/2" centers at 100. Also 3/4" is more on the better end of its performance. It has thrown plenty out in the 1 to 1.5 as well. I think my next step is to change the barrel.

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    Quote Originally Posted by JayAndrew View Post
    Could the barrel be the culprit? Maybe.

    When you start trying to get a gun to shoot under .75” there are lots of little things that could be affecting the accuracy. Some of them not entirely the guns fault.

    What is your shooting cadence?
    Is the barrel heating up and throwing shots?





    Check out my website!
    The Ballistic Assistant
    I would agree. The tests I have been conducting have been all sitting on a bench with a bipod and a bag. I don't claim to be a great shooter, but I have done some classes and have shot other rifles to around 1/4" groups. I do believe there is a problem with the rifle. That's why I have been tinkering with this thing to figure out what could be wrong. I have already gone through the easy stuff which is what led me to casting the chamber. I don't think the barrel is heating up. It seems to shoot poorly consistently.

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    Quote Originally Posted by Anhur View Post
    I wouldn't say defective maybe just disappointing. The model 12 HS is supposed to be their target model. Many others that have these rifles are reporting sub 1/2" centers at 100. Also 3/4" is more on the better end of its performance. It has thrown plenty out in the 1 to 1.5 as well. I think my next step is to change the barrel.
    I'd have to agree that it's not worth futzing with. Easiest way to get something you're confident in would be to change the barrel.

    -Ron

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    Sell it and build a 700 way better triggers available and everything else to build a killer rifle
    Don


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