Somebody please explain this bullet drop.

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emsg19

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M&P 15-22 with 2moa Holosun red dot and roughly a 25 yard zero. Federal 36gr copper plated hollow points. Every ballistic table I've checked, including Federal's own, says on at 25, 1" high at 50, back on around 75, and about 3" low at 100. My results are way different. Check the attached pic. Point of aim was red dot at every distance. On at 25 yards, on at 40, 3.5" low at 60, 5" low at 80, 8" low at 100.

How can the ballistics say 1" high at 50yards and I be 3.5" low at 60? I do realize red dots are not magnified scopes, but I'm still surprised by the difference.
 

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emsg19 said:
Just checked that one too. Same outputs.
Click to expand...
If you list your inputs, I can check for you. I suspect part of the problem might be that your "roughly 25yd zero" is more like 30 yd and you are sighted lower than you assumed.
 
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Common trajectory charts just don't work with an AR-type rifle because the height of the sight line is so far above the bore axis. Most charts are figured with a sight height above bore axis of 1.5", while with an AR it's more like 2.5 to 3".
 
Here's what I got using the Federal calculator, your ammunition, and an optic 2.5" above center of bore. Zero at 25 yards / 5 yard increments / 100 yard distance:

iDsGAT6.jpg
 
bamashooter said:
Here's what I got using the Federal calculator, your ammunition, and an optic 2.5" above center of bore. Zero at 25 yards / 5 yard increments / 100 yard distance:

iDsGAT6.jpg
Click to expand...

That's what I got too. From multiple calculators. I even changed the temp and altitude to be more accurate.
 
Is it possible that I'm not getting the full velocity because the 15-22 is basically an all polymer rifle compared to a more traditional 10/22 type?
 
No, polymer makes no difference....

The numbers make sense to me. Remember that a bullet starts to drop as soon as it leaves the barrel, which is why it is actually pointed up a bit. At close range, the drop won't count for much because of the short time the bullet it in the air. Also, a bullet crosses the line of sight, TWICE. Once going up as a result of the barrel being pointed slightly upward. And when the bullet stops climbing and drops, it crosses the sight line again. Any distance after that point will result in drop below the line of sight. I've seen some loads that are so parabolic as to drop 24" at 100 yards.

AND as has already been said, the parallax on an AR 15 type is 2.5 " above the barrel centerline as opposed to a rifle with a ramp sight mounted on top of the barrel that are .5" above the barrel center.

Whatever distance you set your zero for, subtracting or adding distance increases the deviation from the POA at the line of sight. A FLAT shooting gun like a 5.56 AR at 3000 fps is not as affected by this as a typical .22 round going 1500 fps will be. Also, note how the ballistic coefficient of the bullet affects how a bullet retains velocity. A long spitzer vs a RN bullet will keep velocity longer, and drop less due to the amount of time in flight.

When I load my 30-06 with bullets going 1700 fps as opposed to 2800 fps, there is a big difference in the amount of drop, so LOAD and bullet velocity counts a great deal.
 
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Whether it's one of my 5.56s, 10/22, or my 15-22, I'm always very close to assorted calculators with my range time (using a bench). I have the Holosun HS503C on my latest AR upper. It has the 2 moa dot and 65 moa circle. With a 1/2" riser it's perhaps 1.5mm low of being perfect absolute co-witness. Very, very close to 2.5" and aligns well enough with my MBUS. If you have the same optic with the factory mount, the glass sits a bit high as compared to other red dots.
 
Another consideration -- a 2 MOA dot is a pretty sorry device to shoot with at longer ranges. At 100 yards the best you can hope for is being within 2" of where you think you're aiming. Your potential aiming error at 25 is 1/2" -- try plugging in those figures with the actual zero 1/2" low at 25 and see what you get
 
Thanks for all the input. Someone on another forum also mentioned barrel length being a major factor. Too many variables for a calculator. I'm just going to dial in the zero I want with the ammo I want it zeroed for, then make my own notes at different distances and different ammo to learn the holds.
 
Sounds about right.

You're an inch low at 25...add in sight height above
bore, plus drop at 100 yards from table, and you're
only an inch or so off...
 
Velocity.....

emsg19 said:
Thanks for all the input. Someone on another forum also mentioned barrel length being a major factor. Too many variables for a calculator. I'm just going to dial in the zero I want with the ammo I want it zeroed for, then make my own notes at different distances and different ammo to learn the holds.
Click to expand...

Velocity is the needed variable, regardless of barrel length which affects velocity but it is the ACTUAL velocity you want for ballistic calculations.

That is, the initial velocity, which in the case of guns is muzzle velocity, which slows throughout the flight due to drag.
 
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I'm a new shooter but I took my 10/22 out the other day. Zeroed it at 25 feet then at 50 ft is all the high shots with red dot on center. I had to use ft because 50ft is the farthest my indoor range goes.

Still getting used to shooting but mine is way off hahahh. Have a scope now so next range time should be fun. My 15 22 is on its way, hopefully in 3 weeks.
d018f77013b836679462aec44004944a.jpg


Sent from my SM-N910V using Tapatalk
 
Welcome to the forum. How high is the red dot? I ran your approx 8 yard zero with a sight height of 1.5" with a 40 gr bullet with a BC of 0.125 and muzzle velocity of 1200 (pretty generic). At 16 -17 yards (50ish ft.) it should be approx 1.25" - 1.5ish" high. How does it do with the hard sights? I think you'll really enjoy the 15-22.
 
...adjust it to shoot 1" high at fifty yards...that may get the trajectory right at the other points...
 
I'm surprised this got to post #13 before someone mentioned barrel length when talking about bullet drop!

You also need to chronograph YOUR ammo coming out of YOUR gun in order for the info from a ballistic program to be worth anything - SISO principle!
 
Most .22lr powder is done burning in a 16in barrel.

To experience an 8in drop at 100yds vs 3in would be the equivelant of that 36gr bullet with a rated muzzle velocity of 1260fps somehow falling to a muzzle velocity of under 1000fps. I seriously doubt that's happening.

There may be a bit of rated muzzle velocity loss, but I suspect the main culprit is your measured distances at the range or your sight over bore distance. Your numbers are suspiciously in the direction of an optic mounted low on an AR platform with no standard riser. Pics? Otherwise, the issue is somewhere in the measured distances you are using for zero or down field or both.
 
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