686 accuracy - shoots left with certain .38 spcls loads???

This is a discussion on 686 accuracy - shoots left with certain .38 spcls loads??? within the Defensive Ammunition & Ballistics forums, part of the Defensive Carry Discussions category; I noticed something odd at the range tonight, and I've seen this before. Tonight I had a box of Magtech SJSP 158 Gr .357s, and ...

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Thread: 686 accuracy - shoots left with certain .38 spcls loads???

  1. #1
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    686 accuracy - shoots left with certain .38 spcls loads???

    I noticed something odd at the range tonight, and I've seen this before. Tonight I had a box of Magtech SJSP 158 Gr .357s, and a box of PMC 132 Gr. FMJ .38 SPCL. My 686 was dead on with the .357's, but shot to the right with the .38's. Probably about 3" to the right at 25 yards. It's not caused from flinching or any error attributable to me (at least I'm pretty sure it's not).

    This does not really concern me, as I figure it's the combination of the load and the gun. My question to those that know ballistics (I'm ignorant with respect to this subject, as I'm a factory ammo guy and I do not reload): How common is it for a gun to exhibit such changes in accuracy from the ammo? I understand slight changes, but 3" to the right at 25 yards?

    Also, I always thought an accuracy difference would not be biased to one side - I thought it might just be a larger overall group - left, right, up, down.

    Edit: Post title should be "shoots right..."
    Last edited by PEF; May 3rd, 2014 at 10:30 PM. Reason: Cain't tell me left from me right..
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    I am unaware of what can cause a bullet to move horizontally. I never came across that in all the years I competed. Twist rate, bullet weight and shape all affected where my bullet went to some degrees but never had a problem with certain ammo shooting left or right. Maybe the ammo was crooked. :)
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    I wonder if its not the ammo, but the effects the ammo produce in you.

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    That's because you're leaning toward the left!




    (I couldn't resist that.)
    glockman10mm likes this.
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    VIP Member Array glockman10mm's Avatar
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    It's not unusual. Different bullets leave the barrel with a different gas seal pushing them. The last place of contact for that bullet is the crown as it exits. A bullet made of different material or shape will allow the force of the gas to affect it different at this point.
    Brand A bullet may not have the same softness as brand B, which may allow gas to blow past it on one side or the other, or even top or bottom or a combination and throw it one way or the other. Brand B may be soft enough and have a powder that gives it a better uniform seal as it's pushed down and out of the barrel.

    Things like soft/ hard and bullet base all have an affect on bullet obturation which has a direct affect on speed, and accuracy, and point of impact.

    In addition, bullet diameter variations will have an effect. Your 38 bullets also have a longer jump from the cylinder to the forcing cone.
    In short, it all factors in.
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    Went back to the range today, took several other brands of ammo - these were either 125 gr .357 or 125 gr .38. All were dead on; the only time the shots land right is with the 132 gr PMC FMJ's. Guess I'll use those for other revolvers.
    Aceoky likes this.
    -PEF, a Framer with a Steelie...
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    1. All guns are always loaded.
    2. Never let the muzzle cover anything you are not willing to destroy.
    3. Keep your finger off the trigger until your sights are on the target.
    4. Be sure of your target and what is beyond it.

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    I learned a long time ago ammo and gun need to be matched.

    My Dad and I had consecutive numbered .357s. I traded for his and used the same target handload I had developed for mine. Couldn't hit the broadside of a barn! Had to develop another target load for that pistol.
    Bad Bob likes this.

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