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POI change between different ammo types

Discussion in 'General Gun Discussions' started by xwray, Mar 13, 2012.

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  1. xwray

    xwray Member

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    I realize there is no answer to this open ended question but I'm hoping for sort of a ballpark guess from experienced shooters.

    The question is for handguns only.

    Within 25 yards, how much does changing a cartridge with one bullet weight/design to another weight design would typically change its POI; ie, if I shoot a magazine full of one cartridge and get, say a 6 inch spread on the center of a target, what's the liklihood of the bullets from a different magazine loaded with cartdidges of a different type striking in the same general target area. Are the ballistics so sensitive to cartridge type that you might not even hit the target or might the POI be just a bit off.

    I'm just curious whether or not, after a handgun has been zeroed with a given cartridge, if you could expect most any cartridge type to have the same "general" POI as any other through the same handgun at a 25 yard range.

    Obviously I don't have much to do today and when this thought bubbled up I realized I had never seen it addressed anywhere. Maybe nobody else was dumb enough to ask such a question...
     
  2. tightgroup tiger

    tightgroup tiger Member

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    Any time you change bullet weight your point of aim will change. If you use heavier bullets you will probably find your pistol will be shooting high if sighted for lighter ones.
    If you use lighter bullets it will shoot low if sighted for heavier one.

    In my 357mag. if it is sighted in for 125 gr bullets and I change to 158 gr bullets it will generally shoot as much as 4" high at 15 yds. And that is with both loaded to max.

    Changing from one brand to another will also change things because you have no idea how much powder either company is using.

    Send for one of Midways big catalogs and look at the difference in the fps between the different manufactures. Some of them run about the same fps according to their published data and some are faster or slower.

    Everything, including weather temp will affect ballistics. In cold weather the same load will react differently than in warm weather.

    If you change bullet weight you will be changing your sight elevation if you are fortunate enough to have elevated sights on your handgun

    Hope this helps
     
  3. Stevie-Ray

    Stevie-Ray Member

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    Whenever I shoot my EDC, I shoot it with my own prescribed defensive load only, for this very reason.
     
  4. xwray

    xwray Member

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    I thought that might be the case but was hoping the relatively short range of 25 yards would mitigate the effects.

    thanks
     
  5. A-FIXER

    A-FIXER Member

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  6. 9mmepiphany

    9mmepiphany Moderator

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    If you were shooting a 6" group at 25 yards, I would doubt you'd see much difference..how would you even know you were zeroed?
     
  7. xwray

    xwray Member

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    I wasn't actually shooting such a group...simply a hypothetical to calibrate if the different bullets would group somewhat in the same ballpark or different cities...
     
  8. Keb

    Keb Member

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    Seen it

    Testing a CZ75b with a friend's reloads then with WWB I've seen about 7 inches different.

    Quite a surprise for me.
     
  9. Hk Dan

    Hk Dan Member

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    It won't make much of a difference. I am waiting patiently for the "the sights are made to compensatefor barrel rise" people to chime in...hint--they are not. At 100 yards you might see a difference, with the lighter bullets hitting a bit higher (not lower), but at 25 it's going to be minimal in effect.
     
  10. Saakee

    Saakee Member

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    you roll your own self-defense round?
     
  11. tightgroup tiger

    tightgroup tiger Member

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    It won't make much of a difference
    It will make a lot of difference, bullet weight changes alot of things. barrel rise has nothing to do with it.

    The bullet is usually out of the barrel before the barrel starts to rise from recoil anyways.

    I have been reloading 357Mag for 30 yr plus and every time I change from 125gr to 158 gr I have to change the elevation on my sights to reflect the change.

    That is at 15 yds given the both loads are at maximum which is where I usually load at.

    The minimum difference I have seen is 3-4" height change depending on whether I am changing powder loads. This is with a S&W model 28 with a 6" barrel.

    9mm loads may not be as pronounced because there isn't as much of a difference between minimum and max loads as their is with a 357 mag.

    If you want all your loads to shoot the same point of aim then you will have to start loading your own so you can control this.
     
  12. 9mmepiphany

    9mmepiphany Moderator

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    If you are holding a 2" group @ 25 yards, or better yet 4" @ 50 yards, shooting factory 9mm ammo, you'll see two different groups between 115gr and 147gr slugs.

    My experience has been that the least affected cartridge is the .45ACP when changing between 185gr,200gr and 230gr slugs...these were not +P or mid-range target loads...there is a difference in POI, but it wasn't much
     
  13. Stevie-Ray

    Stevie-Ray Member

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    Negative. My own prescribed defensive load, in this case 230 gr HydraShok. In other words the load that works best in this particular gun out of the many tried.
     
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