Barrel Contour vs Accuracy

Discussion in 'Main Message Board' started by Phil3, Jan 10, 2019.

  1. Phil3

    Phil3

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    I am building a 6.5 x 47 rifle for non-competition paper punching. I am unsure on barrel contour (vs accuracy). Some say a heavier barrel is more accurate due to less whip or less effect from heat. I also hear other factors are far more influential. Barrel length will be 24" or 26".

    The stock I am using has a 1" wide barrel channel at the front of the forend (11" from action face), which is limiting, and may require opening up, but maybe I don't need to (depending on contour).

    Shooting setup is either mechanical front rest/heavy rear bag or bipod (F-Class or Harris), with a rear bag). I am not concerned about heavy weight.

    Phil
     
  2. savagedasher

    savagedasher

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    You can’t have your cake and eat it
    Many of barrels shoot good with a .780 diameter at the front
     
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  3. msinc

    msinc

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    There is a lot that can be said regarding barrel contour and accuracy, most of which is relevant to something else or some other factor to consider. There's really no short answer to this question. Generally, the contour, by and of itself, doesn't have much to do with the barrels ability to put one bullet next to or in the same hole as the last one. I have #1 contour "mountain rifle" barrels that will shoot very small impressive groups. Groups that are just as small as my AMU contour heavy barrels. What I cannot do is keep on getting it with the lighter barrels as long as I can accurately with a heavy barrel. That said, when the #1 is cooled off and ready to go again I am still waiting for the AMU to cool down so I can shoot it again.
    All this don't answer your question of "what contour??". I think for a serious accurate rifle to shoot and have fun with a Remington Varmint contour is a good all around size to try. Heavier has some advantages...if you don't care about the weight. It's generally a little easier to hold one still when shooting and cleaning. Most makers offer an AMU contour or something very similar if you want one heavy. I like as long as reasonable for the free velocity, so most of mine are 28". I find with a bipod the heavier the better. Best of luck.
     
  4. Phil3

    Phil3

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    Thanks. It appears the barrel channel will need to be opened up, since the biggest diameter it can handle is 1" at the forend, and since the front of the forend is just 11" away from the action face, most any heavy varmint barrel is that size or bigger at that point. Now, to figure out how to enlarge the barrel channel.

    Phil
     
  5. Bart B.

    Bart B.

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    Wrap coarse sandpaper around something round that just fits the barrel channel. Sand out what's needed. Repeat with fine sandpaper. Seal and finish as desired.

    Minimum 1/16" minimum clearance to the fore end barrel channel.
     
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  6. varget204

    varget204

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    If you are looking for accuracy and do not like Heavy barrel,i'd go w/# 5 bull Sporter .700 at muzzle of 26" barrel or Lt Varmint .750-.775 at 26" muzzle.They are lighter and can compete w the Heavy varmit barrels that are .812 or bigger.They cool off quicker will fit your stock w/ no modification.
     
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  7. John from MN

    John from MN

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    I like a #5 or a Rem Varmint on guns that endure long strings of fire, but still need to be light enough to carry while hunting.

    A #6 or a light varmint would probably work for you without a lot of sanding.
     
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  8. Phil3

    Phil3

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    I think I may be in for a lot of material removal since the barrel channel is 1.00" at the front of the forend (11" from action face). I calculated barrel diameter for a multitude of barrel varmint/match contours and all exceed 1" at the front of the forend. Add in about 0.050" on either side of the barrel for clearance, and each side of the barrel channel will likely need about 0.100" removed.

    Phil
     
  9. djporter

    djporter Silver $$ Contributor

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    80 or 100 grit sand paper can take off a lot of material in a short time.
     
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  10. Phil3

    Phil3

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    Just curious, what is typically done to refinish the sanded area. I know it will be difficult to see down in the channel, but some of it will be visible, especially against a stainless barrel. My Bell & Carlson stock is olive green with black spider webbing which obviously I cannot match, so is this a Krylon job in my color of choice?
     
  11. Steve Ladino

    Steve Ladino

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    A good custom cut barrel ( Krieger ) which is of a straight taper ( none ) and possibly with a tuner and not front heavy when all done would be my choice, 26" x 1.200
     
  12. Shawnba67

    Shawnba67 Silver $$ Contributor

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    David Tubb has his own barrel contour on his rifles and claims that it is just big enough that any bigger wont shoot any better. D. Tubb is probly qualified to make that claim. I think his is close to a med palma. Just food for thought.

    If you have any lathe access i made a brownells type channel rasp out off allthread and washers with o rings for spacers. I turned a stack of washers on lathe to have a sharp edge it really moved alot of material quickly and stayed semi circular too
     
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  13. Kurz

    Kurz

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    If you look at the contour charts, they ususally list a distance from the breech end to a point on the barrel combined with a diameter at that point. No guessing:

    upload_2019-1-11_8-39-28.png

    "C" is the distance while "D" is the diameter at that distance. The #13 Bartlein above is 0.950" at the 4.350" distance so you will be smaller than the 1.000" you suggest at 11" in your stock.

    Enjoy!
     
  14. msinc

    msinc

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    Suggest you wrap sandpaper around something round and have at it. Sounds simpler than it is....use something round that is as long or close to the length of a sheet of sandpaper. It will be easier to keep the barrel channel straight. An old broom handle cut to length works pretty good sometimes.
    Many guys just use a deep socket and that is convenient because you can quickly pick out the right diameter. It will do it, but even a deep socket is not really long enough to easily keep the channel straight. Also, whatever you choose, it's a good idea to frequently check straightness and also being on center with the barreled action. Lay it in place and make sure you are not sanding more to one side than the other....this is very easy to do when you are not checking. The last thing you want is for it to be off to one side or crooked to the barrel.
    The surest way to sand bevels that look terrible is to get it close and finish by putting the barreled action in place and running a long strip of sandpaper under the barrel and sanding it out by working it like you are polishing a shoe {so to speak}....do it all with the broom handle or something similar.

    If the open cell "filler" of the stock is exposed and it probably will be you should at least seal from water. This can be as simple as masking off the rest of the stock and painting the channel with a good {or several} coats of spray paint. I like to use flat black. Some guys like to get a better seal, like a thin coat of body filler sanded nice and smooth then painted. You can go "whole hog" and coat it with epoxy also. I mean, it's not like water can rot a synthetic stock, you just don't want it to get soaked.
     
    Last edited: Jan 11, 2019
  15. Bart B.

    Bart B.

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    I don't think there's any difference in accuracy across barrel contours. Each one vibrates, whips and wiggles at its unique resonant and harmonic frequencies. How much varies with the cartridge and load. But for each combination, they're 100% repeatable. Fact is, they're the most repeatable part of the system. Except if they have a tuning weight near their muzzle, but once ser, it is repeatable at different amounts and frequencies.

    Adjust everything else to benefit from the barrel's consistent behavior.
     
  16. LA50SHOOTER

    LA50SHOOTER Silver $$ Contributor

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    Then Why do Benchrest shooters use different contours ? - If what you stated was true we would all just use the smallest contour at the cheapest price obtainable and wouldn't care about barrel contour.
     
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  17. dkhunt14

    dkhunt14

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    The thinner the barrel, the less shots before the shots start wondering. Matt
     
  18. Phil3

    Phil3

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    Stock 1.jpg

    Thank you. You said, "The last thing you want is for it to be off to one side or crooked to the barrel". It already is, from the factory. A barreled action does not sit straight in the barrel channel. And the stock wall thickness at the forend barrel channel is thicker on the right vs left (from shooter's perspective). See photo...looks more obvious in person. Enlarging the channel will require removing more from the right vs the left while also making sure barrel sits straight. As an aside, if it looks like the bipod stud holes are also off to the right a bit, they are (mostly rear one). They are not directly in line with the stock centerline (slightly crooked). The entire front end of the stock all seems slightly "off" somewhat in how things line up. I have reservations about trying to work with an already misaligned barrel channel and enlarging at same time.
     
    Last edited: Jan 11, 2019
  19. Evlshnngns

    Evlshnngns

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    For a fun target gun, go as heavy as the stock will open. I have two 26" varmint barrel(.8-.83") 6.5's, I will go heavier next time. I have other options if I'm going for a hike.
     
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  20. Bart B.

    Bart B.

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    Not if the receiver face and barrel shoulder are square to the chamber axis. As the barrel heats up it will put more pressure at one point around that juncture as it expands. Stress increases at that point and shots string in that direction.

    People have put 20 to 30 shots 15 to 20 seconds apart from long, skinny barrels without shots wandering away from point of aim.

    Poor stress relieved barrels of any profile will start shooting away from point of aim as they heat up.
     

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