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Posted: 5/2/2010 9:10:20 AM EDT
M855 25 yard zero 
M855 25 meter zero 
M855 36 yard vs 100 yard zero 
M855 and M193 25 meter zero 
M855 and M193 50 yard zero from 16” barrel 
M193 25 meter, 50 yard and 100 yard zeros from 16" barrel 
100 yard zero 
25 meter vs 50 yard zero, M855 from 16” barrel 
M855 300 meter zero 
M855 200 meter vs 300 meter zeros 
M855 36 yard vs 50 yard zeros 
Except where noted, all barrel lengths are 20 inches. Updated: 05/05/10 |
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My head is full of ... mud.
Could someone explain the starting of the trajectory at a negative number? My bullets leave my barrel and go forward almost straight (though it may seem like they go up due to the way my rifle's sights are aimed) though gravity starts pulling on them immediately after leaving the barrel. |
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My head is full of ... mud. Could someone explain the starting of the trajectory at a negative number? My bullets leave my barrel and go forward almost straight (though it may seem like they go up due to the way my rifle's sights are aimed) though gravity starts pulling on them immediately after leaving the barrel. The bullet starts out below the line of sight, since the sights are set up 2.6" or so over the bore. Twist rate won't make any appreciable difference whatsoever. |
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I always sight mine to shoot 1.25" low at 25 yards, with M193, with the SMALL aperture. Most of mine have BUIS (Troy, ARMS #40, #40L) rather than standard carry handle.
What say you about this practice Molon? Bad habit or OK? Range I normally frequent is 100 yards max. |
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Cool charts, but what is the twist rate for the barrel used and how much would it change for a different rate. Twist rate doesn't mean shit as far as ballistic trajectory. Twist rate is to stabilize longer or shorter bullets. Faster twist rates are needed to stabilize longer (generally heavier) bullets, but can cause issues with lighter bullets, increasing the effects of imperfect bullet construction. |
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I always sight mine to shoot 1.25" low at 25 yards, with M193, with the SMALL aperture. Most of mine have BUIS (Troy, ARMS #40, #40L) rather than standard carry handle. What say you about this practice Molon? Bad habit or OK? Range I normally frequent is 100 yards max. Depending upon variables, that's a very good approximation of a 50/200 yard zero. 
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Should I continue to use the small aperture or the large? - don't recall whether or not Troy is same plane.
I guess it doesn't matter too much though since I would never use the large one outside of 25 yards or so. These days I hardly ever use the larger aperture. Other thing is around here there's not too many long shots - close enough inside 200 yards is close enough. Thanks Molon - always enjoy a moment to pick your brain! |
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Where did the data come from? The OP: Molon What was the barrel length of the rifle used? One of the charts shows 16" and IIRC thats what the others use as well (from previous posts from him regarding zeros) What kind of ammo was used? Labels show, M855, M193, Hornady 55, and 75g TAP What was the initial muzzle velocity? Thats the info we need to really make thoes charts repeatable and relevant. |
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Where did the data come from? The OP: Molon What was the barrel length of the rifle used? One of the charts shows 16" and IIRC thats what the others use as well (from previous posts from him regarding zeros) What kind of ammo was used? Labels show, M855, M193, Hornady 55, and 75g TAP What was the initial muzzle velocity? Thats the info we need to really make thoes charts repeatable and relevant. RIF, I suck at it. 
Thanks. 
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Criitical information missing on 8 of the 10 ballistic graphs is the barrel length that goes with the ballistic data in the chart (e.g., the first chart). Only one person posted that particular question later in the post ––-makes me wonder how many people who viewed this really understand what they are looking at.  The ballistic graph of a 10.5", 16", 20" and a 24" barrel AR are not going to look the same –– even if they are firing the same M855, M193 round (or any round for that matter). Does the OP have an answer to this question? Thanks, vr dsg
–– *EDIT* Apparently while I was posting my question someone else answered (not OP) and said this was repost of 16" barrel. Would be good for OP (who's data it is) to affirm for the group, particular those who have not seen the original older posts. Any similar graphs for military issue M855, M193 for the AR 20" version like this posted previously? .
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Should I continue to use the small aperture or the large? - don't recall whether or not Troy is same plane. I guess it doesn't matter too much though since I would never use the large one outside of 25 yards or so. These days I hardly ever use the larger aperture. Other thing is around here there's not too many long shots - close enough inside 200 yards is close enough. Thanks Molon - always enjoy a moment to pick your brain! Use the small aperture when target shooting and the large for combat. |
| I like that 36-yd zero because it's still a 300-yd zero. This keeps the ranges on the rear elevation drum relevant. For those not using a rear sight with elevation drum, it really doesn't matter. With a red-dot and BUIS, you have to ask yourself if you're even going to take a shot over 300 yds. If the answer is yes, you can learn the hold-overs for ranges out to 500. I think I'm going to try the 36 yd zero and check the height at 100 - looks like it should be about 3" which would be perfect. |
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My head is full of ... mud. Could someone explain the starting of the trajectory at a negative number? My bullets leave my barrel and go forward almost straight (though it may seem like they go up due to the way my rifle's sights are aimed) though gravity starts pulling on them immediately after leaving the barrel. The Russians and some other European countries use (or have used) a 'level barrel' drop chart that does not include anything about the line of sight. This is strictly a technical chart showing the absolute trajectory of the round. You must learn to visualize the line of sight as the constant in shooting. With iron sights, you try to first line up the sights perfectly with that invisible line, then adjust the sights so the bullet hits the target. We always use the line of sight method, which produces two 'zeroes' - the 'near' zero and the 'far' zero*. Because the barrel is tilted up relative to the line of sight, the projectile will cross the line of sight close to the gun (near zero), like at 25 yds, rise above the line of sight, then fall back across it at the far zero point, say 300 yds. This is exactly why the standard military targeting is the 25M zero, and why the rear elevation knob starts at 300M. * there are exceptions where a zero can be selected that has the projectile touching the line of sight at only one place, usually around 100 yards. |
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Where did the data come from? The OP: Molon What was the barrel length of the rifle used? One of the charts shows 16" and IIRC thats what the others use as well (from previous posts from him regarding zeros) What kind of ammo was used? Labels show, M855, M193, Hornady 55, and 75g TAP What was the initial muzzle velocity? Thats the info we need to really make thoes charts repeatable and relevant. The ballistic trajectory on graph # 1 posted by the OP does not look like a 16" (or M4 14.5") trajectory to me if this is from a 25 meter zero. With a 25 meter zero at 175 meters the peak is about 6 inches on his graph (i.e., looks more like a 20" A4 or A2 and not carbine) . IIRC for M4 (14.5" barrel) firing M855 with a 25 meter zero that peak is about 7 inches. There's 2.5" hash marks on the vertical axis of the graphs and the peak is definitely at or just below 6". The zero is not specified on graph but looks to be 25 meters. This doesn't look like the trajectory of a carbine as was suggested. BTW, ballistics between 14.5 and 16 are very close. Would be interesting to find out if these is first hand raw data gathered by the OP, or from aquired from another source. |
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great explanation. iu don't know how many arguments i got in over this. ––––––––––––- so what is the recommended zero? mine's zeroed at 50 yards w/ m193 and has a 16in bbl. 
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| Molon, so somewhere between 25-75 yards lies the "zero distance" for any given barrel length and bullet weight, by which you minimize the max/min deviations in trajectory? I wonder if one could model the bullet's trajectory in terms of a parabola (http://en.wikipedia.org/wiki/Parabola). You could then solve for the equation to obtain the exact distance (for any given bullet length and barrel length [or hence, bullet velocity]) by which the bullet's trajectory deviations would be minimized. |
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Molon, so somewhere between 25-75 yards lies the "zero distance" for any given barrel length and bullet weight, by which you minimize the max/min deviations in trajectory? I wonder if one could model the bullet's trajectory in terms of a parabola (http://en.wikipedia.org/wiki/Parabola). You could then solve for the equation to obtain the exact distance (for any given bullet length and barrel length [or hence, bullet velocity]) by which the bullet's trajectory deviations would be minimized. The concept that you are referring to is the proper definition of "point blank range" and is easily calculated using Oehler's Ballistic Explorer. |
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courtesy of zrxc77.
Thank you, thank you, thank you for posting this chart. It perfectly illustrates the bullet arc. I have argued until my ears bled that bullets don't "rise" after they leave the barrel, and some people simply can't grasp the concept. I'll bet 50% of the people on AR15.com still think bullets magically fly upwards after leaving the muzzle of a gun. Pictures worth a thousand words and all that. . . |
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Just curious.. maybe I missed it,
Molon, What software are you using that shows trajectory like that? I know it is kind of off topic but I am looking to start gettin into shooting with a scope out to longer distances and am trying to find something better than whatever googles comes up with when I type in "ballistics calculator" lol Thanks |
| Ok follow me here for a second. I have an Ampoint Comp ml3 On a Larue 150 high mount. How does having the center of the optic another 1/3 above the irons lower the point of impact at 25 Yards. I ask because its what i have on my rilfe and it always seams to hit about 3 inches low to point of aim at 25. |
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Ok follow me here for a second. I have an Ampoint Comp ml3 On a Larue 150 high mount. How does having the center of the optic another 1/3 above the irons lower the point of impact at 25 Yards. I ask because its what i have on my rilfe and it always seams to hit about 3 inches low to point of aim at 25. The Larue "lower 1/3" cowitness places the center-line of the Aimpoint approximately 2.925" above the center-line of the bore. Where your round strikes at 25 yards, will depend upon your particular zero. For example, a 100 yard zero would give you a point of impact that is approximately 1.8" low at 25 yards. |
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Ok follow me here for a second. I have an Ampoint Comp ml3 On a Larue 150 high mount. How does having the center of the optic another 1/3 above the irons lower the point of impact at 25 Yards. I ask because its what i have on my rilfe and it always seams to hit about 3 inches low to point of aim at 25. The Larue "lower 1/3" cowitness places the center-line of the Aimpoint approximately 2.925" above the center-line of the bore. Where your round strikes at 25 yards, will depend upon your particular zero. For example, a 100 yard zero would give you a point of impact that is approximately 1.8" low at 25 yards. Well i usually give it a zero of 50 yards so about 3 inches low would be about right then. Thanks Molon 
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Ok follow me here for a second. I have an Ampoint Comp ml3 On a Larue 150 high mount. How does having the center of the optic another 1/3 above the irons lower the point of impact at 25 Yards. I ask because its what i have on my rilfe and it always seams to hit about 3 inches low to point of aim at 25. The Larue "lower 1/3" cowitness places the center-line of the Aimpoint approximately 2.925" above the center-line of the bore. Where your round strikes at 25 yards, will depend upon your particular zero. For example, a 100 yard zero would give you a point of impact that is approximately 1.8" low at 25 yards. Well i usually give it a zero of 50 yards so about 3 inches low would be about right then. Thanks Molon In that case, your point of impact at 25 yards should be apprximately 1.3" low. |
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