close

Privacy guaranteed - Your email is not shared with anyone.

Welcome to Glock Talk

Why should YOU join our Glock forum?

  • Converse with other Glock Enthusiasts
  • Learn about the latest hunting products
  • Becoming a member is FREE and EASY

If you consider yourself a beginner or an avid shooter, the Glock Talk community is your place to discuss self defense, concealed carry, reloading, target shooting, and all things Glock.

55g vs Heavier Bullets...POA-POI Differences?

Discussion in 'Black Rifle Forum' started by Agent6-3/8, Dec 20, 2010.

  1. While my AR is not, my primary HD weapon, I'd still like to keep a mag or two on hand of good defensive ammo on hand. (may also end up using it on coyotes at some point) The general consensus seems to be that the heavier bullets are the most effective fight stoppers.

    At this point I'm shooting 55g loads because its what is most readily available in my area. My question is how large of a POI varaition is there once one start stepping up to the heavier bullet weights? I'm sure at nominal SD ranges, its not s concern, but I'm OCD about things...;)
     
  2. Travclem

    Travclem Badass Member Lifetime Member

    6,775
    8
    Aug 4, 2008
    Lubbock, TX
    in my experience you can count on about 1.5" more drop at 100yds with 75gr than with 55gr. I have a 700p and at 100yds the federal TRU 55gr, Hornady 75gr TAP and Winchester ranger 64grsp all grouped within a 2" circle. I shot 5rds of each with the same poa. My AR tested similar to this but I added xm193 to the equation with it.

    For all intensive purposes, there's negligible difference in poi for these rounds. (inside of 100yds that is)
     


  3. TimP

    TimP 1 Proud Infidel

    2,154
    0
    Jan 17, 2003
    NC
    like anything, it will depend on the barrel and ammo combo.

    If the heavier bullets produce the same barrel harmonics as the 55gr, then you should only have to deal with a slight elevation difference as the heavier bullets wont rise as quickly.

    If the harmonics are vastly different, you may toss rounds as far as 2-4 inches off target a 100.

    Simple answer.... you just have to try it and see.


    Here is an example of mine. In the target below you will see three groups. Top left is Blackhills 6.5 Grendel 123gr lapua scenar, middle group is Alexander Arms 123gr Lapua Scenar, and right group is Wolf 120gr MPT.

    The gun was sighted in with the Alexander Arms ammo. As you can see, even though the black hills ( on the top left ) was the same weight, the groups were horrible at 4.25moa, compared to the Alexander arms that grouped .588 inch for the same weight ammo.

    So it really all depends on what your gun likes.

    [​IMG]
     
    Last edited: Dec 20, 2010
  4. glock22357

    glock22357 Got Ammo???

    3,163
    0
    Mar 1, 2004
    Benton Harbor, MI
    Unless you are shooting you AR for maximum accuracy at ranges past 150M, I would doubt that you would notice a POA/POI difference based on bullet weight. Even if you did, it's simply a matter of sighting in your rifle for the load you choose to use and distance you choose to shoot at.
     
  5. glock22357

    glock22357 Got Ammo???

    3,163
    0
    Mar 1, 2004
    Benton Harbor, MI
    Bullets never rise, it's a matter of physics laws.
     
  6. TimP

    TimP 1 Proud Infidel

    2,154
    0
    Jan 17, 2003
    NC
    they have to rise to the line of sight on an optic or iron sights. Whether you want to call it "rising", or moving towards the intersection point for the point of impact and aiming point with the sights.

    it is true, a bullet will never gain altitude if it is shot horizontally from the ground, although if you are shooting at extended distances, you will actually have to shoot "up" causing the bullet to gain elevation, but not on its on.
     
    Last edited: Dec 20, 2010
  7. Boxerglocker

    Boxerglocker Jacks #1 Fan

    6,147
    26
    Mar 6, 2003
    Lynnwood, WA

    :popcorn: Tagged this thread, Newbie wanting to hear and learn.

    One question though, what distance should one zero thier new rifle with a red dot for typical urban combat distances? From what I have read so far, 25 yards then out to 100 for both iron sights and the optic, is what I'm thinking :dunno:
     
  8. TimP

    TimP 1 Proud Infidel

    2,154
    0
    Jan 17, 2003
    NC
    It depends on what optics you are using.

    If you are using something like a Burris XTR, or ACOG, it is designed for a 100 yard zero in order for the reticles bullet drop features to work correctly.

    If you are using a red dot like an Aimpoint, Eotech, another optic without a calibrated reticle or iron sights, I prefer a 50/200 yard zero. It keeps you within 1.5 inches high or low out to 200 yards, and only 7.25 inch low at 300.

    In my opinion the 25 yard zero is a very poor choice. Zeroed at 25yards, you are roughly 4.5 inches high at 100, 6.25-inch high at 150, 6.67-inch high at 200, 5.5inch high at 250, 2.8-inch high at 300, and finally back at point of aim at around 335 yards.
     
  9. plasticslap

    plasticslap

    303
    0
    Oct 16, 2006
    Cary,NC
    Where do I start?....

    Bullets never rise. This is a common misconception due to the large population of people that don't fully understand how their rifle sighting system works. When you look down the irons or through a scope, you are looking along a straight path. The barrel however, is angled in your hands in such a way that the bullet will leave the bore headed skywards at an angle that allows it to fall on the intended target at the end of the scope line of sight.

    If the barrel were held at exactly 0 degrees (horizontal) the round would leave and show the effects of the only two forces acting on it, Gravity and horizontal acceleration. Neither of these acts on a bullet to elevate it against gravity, which is independent of the object's motion along the flight path. Newton explained this by proving that forces acting on an object have no effects on the object's motion that are perpendicular to the force.

    [​IMG]



    Hope that helps.
     
    Last edited: Dec 20, 2010
  10. Bushflyr

    Bushflyr ʇno uıƃuɐɥ ʇsnɾ Millennium Member

    3,524
    0
    Mar 17, 1999
    Western WA
    So let me guess, you flunked both physics and law?
     
  11. NeverMore1701

    NeverMore1701 Fear no Evil Platinum Member

    38,390
    3,714
    Jun 25, 2004
    Amarillo, Tx
  12. plasticslap

    plasticslap

    303
    0
    Oct 16, 2006
    Cary,NC
    Probably not, but I'm guessing you did
     
  13. Bushflyr

    Bushflyr ʇno uıƃuɐɥ ʇsnɾ Millennium Member

    3,524
    0
    Mar 17, 1999
    Western WA
    At no point in the previous discussion was that stated. In fact the only time you would have the barrel at 0 degrees would be if you were shooting downhill. If you are shooting level the barrel is elevated. Therefore the bullet leaves the barrel in an upward trajectory. Upward trajectory = increasing altitude with respect to the datum = rise. :tongueout:
     
  14. MisterPX

    MisterPX Guest

    With 62 gr out of a 14.5 barrel, the 50M zero will have you hitting 300M keeping your dot on target.
     
  15. plasticslap

    plasticslap

    303
    0
    Oct 16, 2006
    Cary,NC
    You just proved my point. Both of them.

    1. If the bore were at 0 degrees, the bullet would go down, as IT ALWAYS DOES. And I know it wasn't stated, it was to provide reference so that the picture would make sense. The bullet is not rising, it is in fact falling. The fact that you change the inclination of its trajectory initially does not magically give it the ability to oppose gravity and rise. You are simply exploiting what is already known as Newtonian physics of projectile motion.

    2. You did fail physics.
    :tongueout:
     
  16. cowboy1964

    cowboy1964

    19,696
    2,133
    Sep 4, 2009
    U.S.A.
    If you have to use 25 yards to zero for 50/200, how low should the POI be?
     
  17. faawrenchbndr

    faawrenchbndr DirtyThirty fan CLM

    36,077
    443
    Nov 24, 2005
    Troy
    I guess your laws are wrong! :dunno:
     
  18. MisterPX

    MisterPX Guest

    1/2 hte distance from your sight plane, to tehmuzzle plane. ON a typical AR, this is about 1.25 inches.
     
  19. MisterPX

    MisterPX Guest

    OK knuckleheads, if your sight plane on a zeroed rifle is level, your bore is pointing UPWARDS. IN order to have your bore level, your sight plane would be aiming DOWNWARDS. YOu guys are dickin around back and forth in somebnody elses thread trying to convince each other the SAME THING.

    ETA: dammit, though bush's quote would be requoted too.
     
    Last edited by a moderator: Dec 20, 2010
  20. MrOldLude

    MrOldLude

    287
    0
    Jan 18, 2010
    This is what happens when someone who has taken highschool physics and tries to apply the most fundamental and generalized case with bad results.