I shot some 68 grain black hills ammo yesterday at 25 yards. If I am zeroed at this range, where will my trajectory be at 50, 100, 200, 300?
If you zero'd at 25 yd, you're going to be shooting low at 50-150 yd IIRC.
What was that shortcut? 50=200?
TO answer this question I need to know what barrel length you're utilizing and then we can guestimate your velocity to determine your on paper ballistics.
Assuming you're on a 20" barrel it should be about:
1/4" high at 50, 1/4" low at 100, 5.25" low at 200, and 16.5" low at 300.
A 16" inch barrel or shorter will be worse.
It's been awhile since my Corps marksmanship training, but if your zero is at 25 you should be zero'd at 300 yards which would put your bullet impact high at everything in between. Someone please correct me if I'm wrong.
If you aim center of mass with a 25 yard zero you'll hit a man out to 300 yards, thats the logic behind that training. However, you will hit 16.5" low at 300 yards.
Not only that, but the training is for bullets that are somewhat lighter and faster than BH 68 grain loads.
For the most part shooting dead on at 25 yards is going to take the bullet high until around 125-150 yards or so then it'll drop below. I don't have my calculator handy.
Would barrel length have any significant effect on bullet drop at those ranges?
It fairly dramatically effects velocity and therefore ballistics, yes - does it change hitting a minute of man at 300? Probably not.
I don't have the military marksmanship manual in front of me, but IIRC I believe it said something like zero your M16 at 32.5 meters (not sure on exact number) and it will give you a battle zero.
Darn, I don't know where some of you learned ballistics - but it sure wasn't in Physics class.
No you would be shooting HIGH (roughly 2" high). The bullet was low PRIOR to 25y, after that it's on a steep trajectory.
With an M4 using M855 - though it's pretty close with M193, 68gr, 75gr with barrel lengths between 14.5" & 16" (not too far off for the 20"ers either).
No, not even close. At 25Y with an AR-15 you will 6"+ at 100y (and the bullet will still be rising).
That was the theory, but you have to remember several things.
1) It was METERS not yards
2) You had to adjust the rear sight (to 8/3 +1 for the M16A2/ 6/3+2 for the M16A4)
3) Even then it didn't work.
That is why the USMC went to zeroing their rifles at 36y because it gave a true 300M zero.
Note the military NEVER zeroed at 25 yards - it's always been 25M for the M16 series (unlile the USMC 36y came out). However, even with a 25y zero yes with a COM aiming point you can hit a full sized (E type) target out to 300y. Note at 250y the round will be 12" high (in the head) so you better not have lots of drift.
At 300y your round will be 11.2" high, at 300M the round is still 10" high, and the round doesn't cross the line of sight till 435yards or so. (assumes a 25y zero with M855 from a 20" barrel - M193 drops a bit quicker but still doesn't cross til 415y or so)
Negative, shooting dead on at 25y with .223 keeps the bullet high to the 400y mark (give or a take a couple dozen yards based on the bullet & barrel).
Back when we had M16A1s we used to zero by shooting at 25M (27.3 yards) with our Long Range Aperture - which gave us a nice 375M long range zero. By flipping back to the unmarked aperture we got a 43M/250M battlesight zero (which is remarkably close to the 50y/200M zero...). The devil is ALWAYS in the details (like fliping apertures or setting the elevation to a higher setting....).
For 99.8% of AR-15 shooters using standard iron sights or optics mounted on the flattop your best zeroing option is to zero at 50 yards. That gives you minute of beer-can from muzzle to 225yards or so with most ammo types. (just re-zero when you change loads). Don't have a 50 yard range? Then there are two other options:
1) At 25yards zero so the bullet strikes roughly 1 1/4" below the point of aim.
2) At 100Y follow Beekeepers note that the bullet should strike roughly 1 3/4" to 2" over the point of aim.
As always it's best to fine tune at 200M (note at 200Y the round should strike roughly 1" high in a perfect environment - dead on is 'good enough' )
Muzzle Velocity: 2850.0 ft/sec
Ballistic Coefficient: 0.355
Drag Function: G1
Bullet Weight: 68 grains
Sight Height: 2.50 inches
Wind Cross Speed: 0 mph
LOS Angle: 0 degrees
Target Speed: 0 mph
Zero Range: 25 yards
Temperature: 56.1 °F
Barometric Pressure: 29.07 in Hg
Relative Humidity: 0.0 %
Altitude: 800 feet
Air Density: 98 % of Sea Level
Elevation: 10.093 moa
Azimuth: 0.000 moa
Range Velocity Drop
(yards) (ft/sec) (inches)
0 2850.0 -2.5
25 2784.5 -0.0
100 2593.8 5.8
200 2352.7 8.8
300 2125.3 5.6
400 1910.1 -5.4
500 1709.8 -25.9
600 1526.1 -58.4
Ahh ok with a 'standard' type rifle I could see a 25y/100y type zero with those sight that are barrely 1" over the bore (note AR-15's Height Over Bore is 2.6").
As this is AR-15.com I took the question to mean AR-15s (especially as most of the responses were related to M16s).
As you can see Sight Height Over Bore plays a significant part of developing a zero for a rifle.
Good stuff, Forest, thanks. When I did my primary marksmanship training at Edson Range it was measured off in meters. On my yearly quals after that most of my range work was on KD ranges out to 250 yards if I recall correctly.
I read somewhere a couple of weeks back that there are only a couple of ranges in the military that are measured in meters and Edson was not one of them, which didn't sound right to me, but who am I to argue. Heck, I still could be wrong!
In the ARMY all the ranges are supposed to be measured in Meters. The USMC IIRC has KD ranges still in yards (some Marines help me out here).
The -10s all refer to meters when zeroing and the makes on the elevation wheel of the A2 sight.
And if you'll notice they all put their optics pretty close (if not on) that magic 2.6" number (Aimpoint, Tacpoint, SPOT, EOTech, LaRue mounts, ARMS mounts, Armalite mount, RRA mounts etc.). The straight (inline) stock pretty much demands it.
Great point! The tables get you started, but you NEED to get the range and SHOOT!
This is all good info - the ballistics I posted we using a very low sight height, IE: 1/2" which does not represent a standard M16A2/AR15A2 sight height. There wasn't much data to work with there - but if you calculate in the height of a A2 sight system, yes, you're high across the board with a 25 yard zero.