Page 6 of 17 FirstFirst ... 4567816 ... LastLast
Results 51 to 60 of 170

Thread: Why not 1/8 twist?

  1. #51
    Join Date
    Dec 2009
    Location
    Utah
    Posts
    8,421
    Feedback Score
    3 (100%)
    What it actually says is-

    .22 Caliber (.224) High Velocity 52 gr. HPBT Match

    For rifles, the 52 grain #1410 bullet offers the shooter all the advantages of a boat tail design for 200 to 300 yard competition. The #1410 is appropriate for rifles with 1x12" or 1x14" twist rates
    Emphasis mine
    INSIDE PLAN OF BOX
    1. ROAD-RUNNER LIFTS GLASS OF WATER- PULLING UP MATCH
    2. MATCH SCRATCHES ON MATCH-BOX
    3. MATCH LIGHTS FUSE TO TNT
    4. BOOM!
    5. HA-HA!!

    -WILE E. COYOTE, AUTHOR OF "EVERYTHING I NEEDED TO KNOW IN LIFE, I LEARNED FROM GOLDBERG & MURPHY"

    http://i115.photobucket.com/albums/n289/SgtSongDog/AR%20Carbine/DSC_0114.jpg
    I am American

  2. #52
    Join Date
    Sep 2007
    Posts
    2,954
    Feedback Score
    22 (100%)
    Quote Originally Posted by Obscenejesster View Post
    Yup, interms of barrel quality being far more important than twist rate, that's what I said a couple posts up.

    Getting onto the fact you think 1/8 twist can barely stabilize a 70gr pill. I have nothing else to say except that this information is false and nobody should be listening to it.

    I've never come across a 1/8 barrel that can't stabilize a 77gr pill let alone one that weighs 70gr. In fact, I'm looking at a box of 77gr Sierra Match Kings and right on the box, it says "1/7 or 1/8 twist only". Most of the precision guys are using 1/8 barrels and shooting either 77gr Sierra's or 77gr Noslers.

    If you look around, you will actually find, most match and SS barrels are only offered in 1/8 twist.

    Maybe you got confused and instead of typing 1/9 you types 1/8. If you didn't get confused then please stop spreading false information. Bottom line....1/8 is plenty fast to stabilize 77gr pills. Hell, some 1/9 barrels can stabilize a 77gr pill.
    You failed to grasp that the 70gr TSX is an ALL COPPER bullet, thus longer but lighter than a 77gr SMK. My information is NOT false.

    The 70 grain TSX has a specific gravity much lower than a copper jacketed/lead core bullet due to its sold copper construction. For example, the Hornady 75 grain BTHP has a specific gravity of approximately 10.3, while the Barnes 70 grain TSX has a specific gravity of only 8.9.

    Quote Originally Posted by MistWolf View Post
    Notice that Barnes lists the 1:8 as the slowest twist. That means 1:8 is the slowest twist they claim will stabilize that bullet. That can mean that it's barely stabilizing the bullet at an acceptable level and the 1:9 will not
    Correct

    The Barnes 70 grain TSX will be unstable from a 1:9” twist barrel with a gyroscopic stability factor of less than 1 at all velocities. The 70 grain TSX will only be marginally stable in a 1:8” twist barrel with a G.S.F. of 1.05 at 2500 fps. A 1:7” twist barrel will produce acceptable stability with the 70 grain TSX with a G.S.F. of 1.37 at 2500 fps.



    credit to Molon for doing the work.
    Last edited by vicious_cb; 02-16-14 at 14:25.

  3. #53
    Join Date
    May 2006
    Location
    VA/OH
    Posts
    29,630
    Feedback Score
    33 (100%)
    Quote Originally Posted by tylerw02 View Post
    Theron lies the problem. Many, if not the majority of stainless match barrels in medium contour come in 1:8". Why does BCM do this if 1:7" is the universal answer? If so, why?


    Sent from my iPhone using Tapatalk
    The BCM 410SS barrels are 1/8 twist because I asked Paul to make them that way. Why did I do that? Because I was realistic in how most shooters would use these barrels (which is varmint hunting). With that said, the bulk amount of .223/5.56 ammo is in the 55gr weight. The 1/8 is going to shoot the 55gr a little better.

    C4

  4. #54
    Join Date
    Dec 2009
    Location
    Utah
    Posts
    8,421
    Feedback Score
    3 (100%)
    Quote Originally Posted by tylerw02 View Post
    I've never heard that bullets have less drag when spun faster...
    Actually, the data shows the more stable the bullet is, the less drag it has because it reduces precession. Sierra found, in the case of their 22 caliber 69 gr SMK that the bullet was more stable with a 1:7 twist than it was with anything slower, including the 1:8.

    Nobody said that spinning the bullet faster means less drag. Over spinning the bullet means it won't nose over and let the nose follow the trajectory which results in increased drag and less stability in flight. That means too much spin results in more drag
    Last edited by MistWolf; 02-16-14 at 14:50.
    INSIDE PLAN OF BOX
    1. ROAD-RUNNER LIFTS GLASS OF WATER- PULLING UP MATCH
    2. MATCH SCRATCHES ON MATCH-BOX
    3. MATCH LIGHTS FUSE TO TNT
    4. BOOM!
    5. HA-HA!!

    -WILE E. COYOTE, AUTHOR OF "EVERYTHING I NEEDED TO KNOW IN LIFE, I LEARNED FROM GOLDBERG & MURPHY"

    http://i115.photobucket.com/albums/n289/SgtSongDog/AR%20Carbine/DSC_0114.jpg
    I am American

  5. #55
    Join Date
    Mar 2013
    Posts
    616
    Feedback Score
    0
    Quote Originally Posted by MistWolf View Post
    Actually, the data shows the more stable the bullet is, the less drag it has because it reduces precession. Sierra found, in the case of their 22 caliber 69 gr SMK that the bullet was more stable with a 1:7 twist than it was with anything slower, including the 1:8.

    Nobody said that spinning the bullet faster means less drag. Over spinning the bullet means it won't nose over and let the nose follow the trajectory which results in increased drag and less stability in flight. That means too much spin results in more drag
    Could you post the data? I'm curious to see what it says.

    Sent from my SGH-T999 using Tapatalk

  6. #56
    Join Date
    Jan 2008
    Posts
    3,714
    Feedback Score
    4 (100%)
    Quote Originally Posted by MistWolf View Post
    Sierra used a doppler radar to show that their 69 gr Matchking bullet was indeed more stable when launched from a barrel with a 1:7 twist vs a 1:8 or 1:9.
    got a link? I'd like to see that info...

    eta: LOL, me too ^
    Last edited by ra2bach; 02-16-14 at 15:30.
    never push a wrench...

  7. #57
    Join Date
    Dec 2009
    Location
    Utah
    Posts
    8,421
    Feedback Score
    3 (100%)
    Sierra printed part of their findings in the Sierra Reloading Manual. I don't know if it's available online or not.

    One place the information about over spinning a projectile can be found in a dissertation written by a U.S. military officer school candidate. I don't recall which branch. There are also other sources explaining the phenomena. It pertains to long range artillery. One case cited an incident where some naval shells were over spun and launched at a high arc. When they came down, they hit the target sideways
    Last edited by MistWolf; 02-16-14 at 15:35.
    INSIDE PLAN OF BOX
    1. ROAD-RUNNER LIFTS GLASS OF WATER- PULLING UP MATCH
    2. MATCH SCRATCHES ON MATCH-BOX
    3. MATCH LIGHTS FUSE TO TNT
    4. BOOM!
    5. HA-HA!!

    -WILE E. COYOTE, AUTHOR OF "EVERYTHING I NEEDED TO KNOW IN LIFE, I LEARNED FROM GOLDBERG & MURPHY"

    http://i115.photobucket.com/albums/n289/SgtSongDog/AR%20Carbine/DSC_0114.jpg
    I am American

  8. #58
    Join Date
    Mar 2013
    Posts
    616
    Feedback Score
    0
    I don't know how this thread turned into a discussion about a couple individual rounds and what twist rates they like better.

    As a general rule of thumb, 1/8 barrels will stabilize most rounds under 62gr better than a 1/7 all things being equal. It will also stabilize all rounds up to 77gr. Some rounds in the high 60's up to the mid 70's well stabilize better coming out of a 1/8 and others will do better coming out of a 1/7.

    Bottom line. Both twist rates will be battle accurate over a wide range of weights.

    I personally own more 1/7 because that is what's widely available in hammer forged chrome lined barrels. I own a couple 1/8's because that is what's widely available in SS match barrels.

    Sent from my SGH-T999 using Tapatalk

  9. #59
    Join Date
    Dec 2009
    Location
    Utah
    Posts
    8,421
    Feedback Score
    3 (100%)
    Here's a post I made concerning tractability (the ballistics of using too much RPM). I edited it because when I posted it, I was being an obnoxious smart ass. I hope the links in this post are still good. You can use the quote to go to the thread and see what others had to say as well as see what a jerk I was being
    Quote Originally Posted by MistWolf View Post
    ...Lungbuster asked about a 1:7 twist, surprised to see barrels listed that tight. Other folks on other sites worry that it's too much for lighter bullets, some citing problems with bullet tractability. I brought it up to show that it's of no concern to the AR shooter.

    Ballisticians say it exists-

    http://www.nennstiel-ruprecht.de/bullfly/tractf.htm
    http://www.nennstiel-ruprecht.de/bullfly/fig15.htm

    From another site dealing with naval weapons fired at high angles: "If the projectile is spinning too rapidly, then the bullet is said to be "overspun" or overstabilized, and in such cases one does indeed find that the so-called 'summital yaw' -- i.e., the cant at the top of the trajectory (where air resistance is least) is too large. It can be -- in extreme cases -- too large for the projectile to 'turn over' at the summit, and it will then fall base down."
    http://www.navweaps.com/index_tech/tech-043.htm

    From a naval academy thesis paper: "A round’s tractability describes the rounds ability to let its longitudinal axis follow a bending trajectory. A round may cease to be tractable if it is over-stabilized. A round becoming over-stabilized is more common with high-angle shooting. Over-stabilized occurs when that the round is rotating too fast and becomes unable to follow a bending trajectory (see Figure 2.1) [Ref. 4].

    http://www.dtic.mil/cgi-bin/GetTRDoc...f&AD=ADA435653
    INSIDE PLAN OF BOX
    1. ROAD-RUNNER LIFTS GLASS OF WATER- PULLING UP MATCH
    2. MATCH SCRATCHES ON MATCH-BOX
    3. MATCH LIGHTS FUSE TO TNT
    4. BOOM!
    5. HA-HA!!

    -WILE E. COYOTE, AUTHOR OF "EVERYTHING I NEEDED TO KNOW IN LIFE, I LEARNED FROM GOLDBERG & MURPHY"

    http://i115.photobucket.com/albums/n289/SgtSongDog/AR%20Carbine/DSC_0114.jpg
    I am American

  10. #60
    Join Date
    Sep 2009
    Location
    South La.
    Posts
    1,892
    Feedback Score
    9 (100%)
    .


    FWIW...
    ... being surrounded in the chemical industry with large gas & steam turbines and seeing the acronym "RPM" being used on this thread, I always found it impressionable that out of a 1-7" barrel an SS109 (62 gr) muzzle velocity RPM is over 300,000 RPM.

    300,000 RPM will generate a doubting dumb look out of an "engineer" as he switches his cellphone over to calculator mode to prove you wrong.

    Again, …FWIW…

    .

Page 6 of 17 FirstFirst ... 4567816 ... LastLast

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •