How come the barrel is this way?

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by hatfield954, Mar 31, 2011.

  1. hatfield954

    hatfield954 Well-Known Member

    Messages:
    125
    Joined:
    Feb 7, 2011
    I have a savage model 12 with a 26 inch barrel in.308 caliber. The twist rate for the barrel is 1 in 10. After cleaning the rifle the other day, I looked through the barrel just to see what it looks like. I wanted to see if it was clean. I noticed the rifling is the full length of the barrel. How is the twist a short distance and the rifling the whole length of the barrel? Seems to me, the rifling would only be 10 inches, since that's the twist rate. Who knows about this one?
     
    Last edited: Mar 31, 2011
  2. onzah

    onzah Well-Known Member

    Messages:
    53
    Joined:
    Oct 10, 2006
    The twist rate only indicates how many inches it takes for the rifling to make one full revolution.
     

  3. gr8whyt

    gr8whyt Well-Known Member

    Messages:
    96
    Joined:
    Nov 26, 2010
    onzah is right. The rifling in the barrel is cut, swaged, or some other method the full length of the barrel at a rate of 1 full turn in 10 inches. Faster twist rates would be 1 in 9 or one in 8. Slower rates would be 1 in 12 or 1 in 14, for example. The chamber is reamed and a very small area in front of the chamber is reamed straight at the groove diameter. That area is called freebore or leade and for your .308 it's about 0.11 inch tapering for about another 0.25 inch until lands are full height. The rest of the barrel retains the original rifling all the way to the muzzle.

    -- gr8whyt
     
  4. Moman

    Moman Well-Known Member

    Messages:
    827
    Joined:
    Feb 7, 2008
    gr8whyt, that's interesting with the leade tapering .011 for .025: Is there a formula for this? How do you figure the taper and length of taper?
     
  5. hatfield954

    hatfield954 Well-Known Member

    Messages:
    125
    Joined:
    Feb 7, 2011
    So, in redthroat terms. You are telling me that the first 10 inches past the chamber has a tighter diameter than the rest of the length of the barrel. Am I correct on that gr8whyt?
     
  6. backwoods83

    backwoods83 Well-Known Member

    Messages:
    2,206
    Joined:
    Jan 8, 2011
    You have a 26" 10 twist, 3"s of your barrel is chamber, so you have 2.3 complete twist and from the start of the rifling to the end of it at the muzzle there should be no more than .0005" difference in the lands and grooves.
     
  7. LouBoyd

    LouBoyd Well-Known Member

    Messages:
    770
    Joined:
    Oct 15, 2007
    Have any of you guys noticed that it's April 1?
    You've been had ;-)
     
  8. noneck180

    noneck180 Well-Known Member

    Messages:
    159
    Joined:
    Sep 16, 2009
    I sure hope thats the case..
     
  9. gr8whyt

    gr8whyt Well-Known Member

    Messages:
    96
    Joined:
    Nov 26, 2010
    No, the leade is straight (no taper) from 2.0488 inch to 2.1388 then begins a taper to 2.3025 inch. This is from the SAAMI drawing here

    -- gr8whyt
     
  10. backwoods83

    backwoods83 Well-Known Member

    Messages:
    2,206
    Joined:
    Jan 8, 2011
    What a jackass! :rolleyes:
     
  11. hatfield954

    hatfield954 Well-Known Member

    Messages:
    125
    Joined:
    Feb 7, 2011
    No backwoods, it wasn't a set up for april fools. I simply wanted to know why. I am not new to guns, I have always been able to shoot good. Even in the military. I am now paying more attention to function instead of my being able to make a gun function. I am doing all my shooting by myself now and paying more attention to getting as accurate as possible.
     
  12. rscott5028

    rscott5028 Well-Known Member

    Messages:
    2,608
    Joined:
    Apr 18, 2010
    If the rifling stops before the end of the barrel, the bullets would be shreaded.

    If I'm not mistaken, this was an actual problem that Savage had with a few early model 12's that didn't get rifled properly. People had to send their rifles back to get rebarrelled.

    For some reason, the millitary glosses over a few details when training some of our people. I knew a Marine that thought that the M16 223 was more leathal because the bullets tumble in flight. (i.e. intentionally designed to do so)

    -- richard
     
  13. 1984nitro

    1984nitro Well-Known Member

    Messages:
    145
    Joined:
    Mar 21, 2010
    I hear what you are saying they try to make it simple to get more people through. I can tell you though that the some marines are teaching the 5.56 nato is out of Concentric on purpose to make it tumble on impact. I have heard it somewhere down the line when in the marines and my wife tried to tell me the same because they told her that at the rifle range. I would have to say this is wrong simply for the fact they use the same round for Designated Marksmen in the squads.

    As for the question its not a bad one, If you don't understand just ask we all had to do the same but forget sometimes that we also had to learn.