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Thread: What’s With My Grouping Here

  1. #41
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    Quote Originally Posted by MistWolf View Post
    Inconsistent pressure on the non-free float forearm. My guess is you're a r/h shooter. Putting pressure on the rifle while resting the forearm on a sandbag will push the barrel up and right, causing the group to string down & left
    I am not following what you are saying here; are you saying that pressure on the barrel when rested, pushing the barrel up and to the right, will cause POI shift down and to the left?

    Or are you saying that a group shot with pressure on non-freefloat forearm will result in shots impacting high and to the right of POA?
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  2. #42
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    Actually, I was thinking of how moving the front sight changes point of impact. Move the front sight to the right and point of impact will move left. Move the front sight up and it will move the point of impact down
    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"

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  3. #43
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    If you mechanically adjust front sight, yes, because you will adjust your line of sight accordingly, thus altering the angle of the bore axis in relation to the LOS. If the bore axis is altered, but the LOS stays the same, you will have POI shift to the same direction the bore axis is altered.
    Last edited by Arctic1; 07-20-13 at 19:38.
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  4. #44
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    Flexing the barrel up raises the front sight. The barrel, due to leverage, will flex closer to the receiver. Now, the shooter will have to angle the rifle downward to realign the rear sight with the front. As the barrel remains fairly straight at the muzzle and the bullet departs inline with the bore, this will result in the shots striking low.

    If the shooter were using an optic mounted close to the eye, flexing the barrel upward would send the shots high because the optic only aligns with the target on one plane, not two as is the case with iron sights
    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
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  5. #45
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    Maybe it's me, but I cannot get that to make any sense.
    Flexing the barrel will alter the bore axis, yes? If the barrel shifts at the receiver, it needs to shift at the muzzle as well. If it has any effect on the front sight it must affect the muzzle and bore axis as well.

    The LOS change cannot be as radical as you are claiming. Also, an upwards adjustment of the front sight, and increased angle of the bore axis, and a downward tilt of the weapon to align sights should cancel each other out, no?
    Last edited by Arctic1; 07-20-13 at 20:28.
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  6. #46
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    Quote Originally Posted by Arctic1 View Post
    Maybe it's me, but I cannot get that to make any sense.
    Flexing the barrel will alter the bore axis, yes? If the barrel shifts at the receiver, it needs to shift at the muzzle as well. If it has any effect on the front sight it must affect the muzzle and bore axis as well.

    The LOS change cannot be as radical as you are claiming. Also, an upwards adjustment of the front sight, and a downward tilt of the weapon to align sights should cancel each other out, no?
    No. The flexing is contained between the weight of the shooter and the rest. There may be some flex at the upper, but it is minimal in relationship to the rear sight. Most of the flexing of the barrel will be between the chamber and the rest. Ahead of the rest will remain straight. Even so, the bend would be a parabola, not a straight curve and the barrel will be straight at the muzzle. Also, the bullet will depart at an angle inline with the bore at the muzzle.

    The shooter aligns his sights with the target, then leans their weight on the rifle. This bends the barrel, deflecting the barrel upward. Left in this position, the bullet will fly high. However, when looking through the rear sight, the shooter sees the front sight is high and angles the muzzle downward to bring the sights back on target. This angles the bore downward, causing the bullet to fly low. It has the same affect as either a) raising the front sight, or b) lowering the rear sight to drop the point of impact.

    Take a piece of PVC pipe and fix it with something to act as sights at either end and line it up without flexing the tube and look at the angle at the "muzzle". Then without changing your position, bend the pipe with the curve pointing towards the floor and again align the sights with your eye on the same target. You will see with it bent so, the "muzzle" end of your pipe is angled downward in compared to when it was straight
    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

  7. #47
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    Quote Originally Posted by MistWolf View Post
    Again I ask, how did you rest the carbine? If it has a non-free float barrel, it can shift the point of impact according to how much pressure was placed on the forearm- and where that pressure was placed.
    This has really been addressed in at least 3 posts. But, since you missed them, my left arm was resting Under the gun. Gun resting on sand bags.
    Last edited by wingspar; 07-21-13 at 01:22.
    Gary
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  8. #48
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    Quote Originally Posted by Iraqgunz View Post
    This thread is actually getting to be ridiculous.
    I would tend to agree. I’d like to be able to come back to this thread later once I’ve had time to digest the info and get back to the range, but in the meantime, it’s kind of gone off subject.

    Quote Originally Posted by Iraqgunz View Post
    Until you actually reset the mechanical zero and use the small aperture and go out and shoot you're just pissing in the wind without any results.

    I would also find an experienced shooter to go with you to help diagnose the issue and rule out any other issues.
    I’m kind of rationing ammo right now as I imagine many of us are forced to do due to the panic buying and lack of ammo available. I live hours from any decent size town or city where instruction is available, and that comes down to ammo and cost. I’m certainly not new to shooting, and my 30-06 group in my original post says I must be able to shoot, but in all honesty, I’ve never been that accurate with my AR. Some days yes, some days no.

    I’ll get back to the range when I can and start all over at 25 yards with the small aperture then move back out to 50 yards, and post back with the results.
    Gary
    Will Fly for Food... and more Ammo

    Alcohol, Tobacco, & Firearms should be the name of a convenience store, not a government agency.

  9. #49
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    Quote Originally Posted by dash1 View Post
    When going from one to the other aperture it usually causes a small windage adjustment. (Look at the sight as it spins on the screw when you flip it). Having zeroed with the large and then going to the small aperture could account for the misses. Use a larger target to see where the rounds are going. My guess is that you will find them grouping to the right. Although, the windage adjustment shouldn't be that noticeable at 50 yards.
    The other peep is offset slightly to compensate for this.

    What is is likely doing is moving his POA ABOVE the target as the large is a 200M and the small apeture is a 300M zero.
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  10. #50
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    I have to make a correction on my assertions on the shift of the point of impact caused by the pressure on the barrel when the rifle is placed on a rest. Arctic1 was indeed correct for questioning my claims. For further clarification please see this thread- https://www.m4carbine.net/showthread...=1#post1702309

    I'm blaming it on dyslexia!
    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

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