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Posted: 3/18/2003 7:05:06 PM EDT
| I was at the range trying to achieve my battlesight zero. Which I could do but my windage is now one notch to the left. Not one of the long ones but the first short one so it might be a half. to compensate for my groups all being to the right. Hardly no wind to blame it on. I was just wondering if it was my gun or normal. Or could it very well be me. I considered myself to be a pretty descent marksman. I could hold good grouping on the 50 yrd and 100 yrd. I guess its no big deal. My weapon is a Colt A2 barrel stamping C MP hbar 1/7 20" on a Bushmaster lower. only 250 rds fired through this weapon. not on that day of course. also this barrel is not chrome lined is that a big deal for accuracy and or longevity, but I guess that is a whole other conversation. |
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I'm kind of lost on your question. My basic run down for shooting 100 yard targets is to let the very first round fly off target to foul the clean barrel, then put three on the paper to figure out where the rifle is hitting that day; If the wind, temperature, and conditions stay constant, all is needed is the first sight correction to keep me in the x-ring If your question is if it's normal for you to have to re-adjust your sights day by day, then yes, it's normal. Ammo speed will change due to a few things, temperature being the big factor. As the bullet speed is changed, due to the different burning characteristics of the same gunpowder/ammo with a change in temperature, the barrel harmonics/bullet exit point of the bullet will change. On your rifle, the gun powder burn rate/change in ammo speed due to temperature/environment change could cause the exit point of the muzzle to be in a differant place, all because the standard speed of your rounds has changed due to as little as a 10 degrees temperature change. It's not only wind that can change the windage of the shot down range, but also the amount of time that the bullet travels down the barrel and the exit point of the muzzle when the bullet exits the barrel. ______________________________________________ Barrel harmonics/end whip is best describe as the barrel end moving in a oblong circle with two long end points in the movement as the bullet travels down the barrel(pressure and torque of the bullet on the barrel). As the bullet exits the barrel, the exit point of the muzzle will be in motion. The ideal exit point for the bullet to exit the muzzle is on one of the end flex points of this circle. At either ends of one of these two points (end flex), the muzzle is at a longer semi-stationary point regarding the ability for the bullet to exit the barrel while (the bullet) having deviations of speed from shot to shot. If the ammo is not tuned to exit the barrel at one of these two end points, then the ammo is exiting during the long muzzle travel from one end stroke to the other. Since the muzzle is at it's greatest movements when traveling from end point to end point, the standard deviation of the bullet speed will cause the group to have a spread. If the muzzle whip is from bottom right to upper left, then the group will be strung out the same way. If you can tune the ammo/bullet to exit the barrel during one of these end semi-stall points, then the group will be tight, due to the end of whip/lag/stall of the muzzle in the semi-opposite re-direction. Hope this helped, Dano |
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Looking at fight4yourrights responce, I may have went off the deep end. If your rifle will sight within 13 clicks of the center mark on the rear sight, then the sights are within Mil-Spec. But note, If you change ammo, you will need to re-sight in the rifle due to barrel harmonics to the new ammo type. |
| Thank both of yall(yes I'm from TEXAS). Dano your information was very informative. I counted the clicks and it is 7 clicks of center. so it is normal. I really appreciate this web site I'm new to the wonderful AR world Ive only owned mine a few short months. This is a great site Thanks to all. |
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