polygonal vs traditional riflling

Discussion in 'Gunsmithing Forum' started by kuntreebouy, Oct 19, 2013.

  1. kuntreebouy

    kuntreebouy New Member

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    ok, I know from what ive read that polygonal barrels have higher vel. readings due to less gas escaping and they last longer, but I couldn't find a str8 forward answer on which is more accurate in a rifle, I figured some seasoned guys on here can probly give me the str8 forward answer im lookin for,, which barrel would make a rifle more accurate??????????
     
  2. DrumJunkie

    DrumJunkie New Member

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    The only thing I have found that polygonal rifled barrels have that the others do not is the lack of ability of using lead slugs. I've seen no added accuracy. In fact the biggest user of such rifeling is used in Combat handguns that are not known to be tack drivers.
     

  3. danf_fl

    danf_fl Retired Supporter

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  4. Mercator

    Mercator Active Member

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    I have not encountered a long gun with polygonal rifling, only handguns. I don't think accuracy is the main point of PR. A PR bore is easier to maintain. There are no grooves to hide the dirt, or to wear off and shorten the barrel life. Companies play with long gun rifling every now and then. I don't think Marlin has been able to prove that its micro rifling beats others. Back to PR, it is a nice feature but for most of us not a game changer.
     
  5. hiwall

    hiwall Well-Known Member

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    It is like saying Chevy motors are better than Ford or Dodge. They are just different.
    Marlin is kinda funny, they made their reputation with Ballard rifling then switched to 'micro groove'.
    Just like anything else you can likely find those that swear by it and those that swear at it.
     
  6. JonM

    JonM Moderator

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    I find it hilarious people jump all over themselves fighting to get a pre remington marlin with the microgroove. The ballard style works muuuuuch better with the 405 bullets and is the same as a microgroove with the 300-350 bullets.

    Marlin switched to microgroove as a cost saver which led to decreased sales due to poor accuracy with most 45-70 loads. When freeeom got em they retooled to ballard style in the old old marlin way producing superior barrels...

    The new marlin 45-70 is what i consider a sleeper gun that a lottttt of folks are cutting off their nose to avoid.

    The problem with polygon rifling is it creates very very high pressures in a normally safe cartridge. Thats why glocks go kaboom more often than other handguns when a oopsie cartridge makes it through inspection. Glocks that convert to standard rifling dont have a kaboom issue.

    When you step up the pressures to rifle cartridges you start turning firearms into grenades. Thats why you dont see much poly rifling.
     
  7. Mercator

    Mercator Active Member

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    I think it is overstated. If the Kahrs and the HK's went kaboom because of their polygonal rifling, I've never heard of it.
     
  8. KG7IL

    KG7IL Well-Known Member

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  9. JonM

    JonM Moderator

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    they dont have unsupported chambers coupled with the poly rifling. mot handguns can take a lot of pressure with proper design. my point is poly rifling increases pressure and isnt normally a issue in handgun rounds
     
  10. kbd512

    kbd512 Well-Known Member Lifetime Supporter

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    HK's have gone kB!, but polygonal rifling didn't have anything to do with it.

    If you have a gun with a high pressure cartridge and an unsupported case head, sooner or later it's gonna cause problems, even with underloaded factory ammo.

    Most kB! are improperly loaded hand loads and a lot of them are way over pressure specs, which is why hand loading requires a lot more effort than most people put into it for it to be as consistent and reliable as factory ammo.

    Yes, because the engraving process produces more force in polygonally rifled bores, the pressure is a little higher. It's still not that high. As for increased velocity, any velocity increase, like the pressure increase, will be marginal at best.

    The quality of the barrel, and most importantly its heat treatment, has a lot more to do with the longevity of a rifled bore than anything else. The best barrel steel in the world is relatively easy to ruin with a poor quality heat treatment.

    There's no significant difference in bore erosion between polygonal and land/groove rifled barrels. Almost all barrels that are worn out will have worn out throats and muzzles before erosion of the bore is a significant factor in the accuracy of the gun.

    Basically, either is just fine for general purpose shooting. Most competitive target shooters I know or have encountered use conventionally rifled pistols and rifles. There's no reason why either form of rifling could not produce superb accuracy, but the cost of polygonal rifling generally prohibits all but the largest manufacturers from using it and it is mostly used for applications where cost is a major factor, like production of military/law enforcement pistols and rifles is concerned. They produce a lot of barrels, so the cold hammer forging machines are the way to go.
     
  11. kuntreebouy

    kuntreebouy New Member

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    i was just curious about it, I had never really thought about it until a guy I know built a AR and put a noveske polygonal barrel on it and was talking about how great it was for basically life expectancy of the barrel, after he went on and on and on,,,,, and did I mention he went on about the barrel and how great it was, I started wondering what the real truth behind it was and if it would make the accuracy better or worse, why the cost was so high, etc. after looking on the innerweb about it I couldn't really find anything about the accuracy of them, just that high dolla manufactures used them on there guns and the production of the barrels themselves were more costly due to million dolla hammer forging machines,, and personally I prefer accuracy over anything myself, hopefully ill be able to answer questions in the gunsmithing forum with you guys before to terribly long, I have always loved tearing guns down and tinkering with them and plan on taking a gunsmithing course after I get xmas done and paid for and the new year kicks in, thnx for all the comments on the question guys
     
  12. kbd512

    kbd512 Well-Known Member Lifetime Supporter

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    The real truth behind barrels is that heat and/or cryo treatments are critical, 4150 may make a difference for full auto but means nothing to a target shooter.

    The ammunition, chamber, muzzle, and plumb face of the bolt have more to do with accuracy than any type of rifling ever will.

    ALL barrels, whether land/groove or polygonal wear out faster in the throat and muzzle faster than the rifling does, the throat because of the miniature explosion that the barrel contains (very hot) and the muzzle because of gas cutting and damage from careless use.

    Yes, the engraving process wears out the rifling with use and higher pressure, higher velocity cartridges wear out the rifling faster.

    The types of things you'd do to an AR to make it more accurate are pretty much the same things you'd do to any other rifle. Make sure the mating faces between the parts are perfectly plumb, decrease tolerances between those components, make the barrel more rigid by adding mass to it (contrary to all popular belief you can't make something more rigid by removing material from it in a "special" way but you can increase its surface area for slightly faster cooling), make sure the muzzle crown is as close to perfect as it can be, decrease lock time, and make the trigger as smooth and crisp as it can be. Oddly enough, in semi-auto rifles recoil spring quality makes a difference (not night and day, but there is a difference), too.

    Basically, build quality and ammunition quality have a lot more to do with accuracy than special rifling. It may be that Noveske build quality and barrel tolerances are exceptional, which would indicate why it is more accurate and/or consistent than other rifles with general production quality components, machining, and fitment of parts.

    In short, there's nothing special about the rifling but if your shooter friend wants to believe that, then :).
     
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