Zeroing question re: same point of impact at two distances.

[Socratactical]

Please help me with the arch of trajectory issue because I am trying to sight in a rifle.

My understanding is that the point of impact will be the same at 25 yards as it is at a greater distance because of the way the bullet arches. However, I cannot remember what that second distance is. Is it 25 and 100? Thanks.

 

[EddieCoyle]

It depends on the bullet, the speed, and height of the sights above the bore.

What kind of rifle?

 

[Socratactical]

AR15 w/ 16 inch barrel.

 

[Big Daddy 45acp]

Without knowing the ammo you are using, it's hard for us to help.

Try this link: Ballistic Calculator

 

[mike93lx]

It is called battle sight zero and is likely 25 and 300 yards for an AR in 223

Exactly what sights are on the rifle?

 

[copterdoctor]

http://ar15zeroing.com/

 

[Socratactical]

Thanks, Mike. Now we're touching an answer. I have an AR15 with a 16 inch barrel. I'm not sure what you're asking when you ask me what the sights are. I can tell you I'm using iron sights on a detachable A3 handle with a 6/3 elevation marking on the rear sight knob.

 

[Jose]

More importantly than what sights are on the rifle, the key questions to answer you correctly are what are the ballistic coefficient, weight, and muzzle velocity of the projectile you are shooting.

With that info and JBM ballistics, an accurate answer can be provided.

 

[Fixxah]

36 yds/300yds in an AR with irons using LC 5.56mm/55gr. comes to mind. This is what I remember 0311 telling me.

 

[mike93lx]

To Jose's point, this isn't generally an exact science and is useful for exactly what it's called, "Battle Sight Zero". It should get you on target at xx yards and xxx yards, but isn't perfect.

With a carry handle setup (and "typical" ammo), I'm pretty confident with my mention of 25/300. That should be close, but you'll need to test it on your rifle and ammo.

 

[fubar]

Battle Sight Zero is a concept for " Good Enough " when shooting at people at a spectrum of ranges. It's a setting for "Minute of Torso " from 0 - 250/300 yards.

I believe in 1982 an M16A1 with a 20 inch barrel hit the same POA @ 25m and 250m. If you zero your rifle at 25 yards , like so many do , it will still be climbing at 100 yards - but only a few ( like 2.5 ) inches.

Before you get the right answer you need to figure out the right question.

 

[FPrice]

Here is a discussion of the Improved Battlesight Zero proposed by Chuck Santose. It might help explain some of what I think you are asking.

http://grburnett.us/guns/ImprovedBattlesightZero.pdf

SWAT Magazine had a good article about a year ago comparing several of the most common zeroing techniques and their results. If I can find it I will post it or it's location.

 

[Jose]

FWIW, for my purposes a 50/200 yard BSZ makes more sense than a 25/300 meter one.

with the 50/200 BSZ the trajectory of the bullet is MUCH closer to the line of sight between 0 and 200 yards than with the 25/300 m BSZ and impact is only 10-11 inches low (about 3.5 MOA) at 300 yards. Since the aiming reference on my sight (Aimpoint CompC) is 4 MOA, putting the dot on the shoulders at 300 will get that bullet home right quick.

 

[Remsport Mfg]

Rule of thumb 50yard is the same at 100yards. When we teach LE patrol rifle this is how we have them zero. This holds true and is one of the basic zero methods.

 

[P-14]

Targets for the AR have been provided by Dench, here: http://www.northeastshooters.com/vb...r-Zeroing-Target?highlight=M16+zeroing+target

This includes links to pdfs of them.

 

[Deer_KiLLer]

Rule of thumb 50yard is the same at 100yards. When we teach LE patrol rifle this is how we have them zerro. This holds true and is one of the basic zerro methods.

50 yards is -1/2 of your 100 yard zero.. if your 1" high at 100 your 1/2" high at 50 for an example.. but if your an unseen 1/4 high at 50 your 1/2" high at 100.

for the best zero follow threw on sighing in, get your point blank and then fine tune it all the way out to your max range, ounce your fine tuned to hit at your max range you should be able to reverse your shooting back down to 25 and almost make a perfect arc chart when your done.

but with certin sights etc, you can dial in your range, you set you max range adjustment fine tune it in and then all the other fall into place, and then you have a battle field zero in there, set it on 3 and hit anything you aim at out to xxx range.

sighting in at 25 to hit 300 is a point blank zero, its just a place to start.. then check is it center at 100 is it around 2"or what ever a ballistic chart say it should be ok set. now do it again at 200 and then 300 etc.

 

[EddieCoyle]

FWIW, for my purposes a 50/200 yard BSZ makes more sense than a 25/300 meter one.

This is the way I zero my ARs.

 

[Admin]

FWIW, for my purposes a 50/200 yard BSZ makes more sense than a 25/300 meter one.

with the 50/200 BSZ the trajectory of the bullet is MUCH closer to the line of sight between 0 and 200 yards than with the 25/300 m BSZ and impact is only 10-11 inches low (about 3.5 MOA) at 300 yards. Since the aiming reference on my sight (Aimpoint CompC) is 4 MOA, putting the dot on the shoulders at 300 will get that bullet home right quick.

+1

All my sticks are zeroed at 50.

 

[RKG]

Likewise:

Load: 26.0 gr. Win748, Win 55 gr. FMJ, cases mixed mil., CCI SR primer, for approximately 2,600 fps MV. Rifle is M4 clone; sightline is +2.5" over bore.

50 Yds: +0.0"
100 Yds: +1.5"
150 Yds: +1.5"
200 Yds: +0.0"
250 Yds: -3.2"

Mid-range (max. elevation in flight) is +1.8 " at about 125 yds.

 

[center442]

Would these same rules/formulas hold true for a sight like an Eotech? Or a conventional scope?

My personal experience would seem to indicate that it would, at least for the Eotech. If I sight it at 50 yards, I can hold pretty easily on an 18" square steel plate at 300. I haven't really tried yet with a conventional scope.

Just wondering what I should expect.

ETA: I said 300 yards; thinking about it it may have been 250. I'll have to double-check the distance next range trip.

 

[wf217]

+1

All my sticks are zeroed at 50.

+1 for 50 yrds

 

[Flyer007]

ACOG here zero'd for 100 so that the elevation offsets will be correct.

Happy to say I tested the elevation offsets out to 450yds last week. First shot on steel

 

[Lamina]

ACOG here zero'd for 100 so that the elevation offsets will be correct.

Happy to say I tested the elevation offsets out to 450yds last week. First shot on steel

Has me wanting an ACOG bad.

 

[Admin]

Has me wanting an ACOG bad.

They don't work too well when you tape over them though.

 

[RKG]

Would these same rules/formulas hold true for a sight like an Eotech? Or a conventional scope?

My personal experience would seem to indicate that it would, at least for the Eotech. If I sight it at 50 yards, I can hold pretty easily on an 18" square steel plate at 300. I haven't really tried yet with a conventional scope.

Just wondering what I should expect.

ETA: I said 300 yards; thinking about it it may have been 250. I'll have to double-check the distance next range trip.

The factor that varies with the type of sight is limited to the height of the sightline over the muzzle. If that remains the same, then the calculations are valid regardless of the type of sight employed.

 

[Deer_KiLLer]

with battlefield zero point blank zero etc.. you can sight in to favor its limits for more longer range use or to favor closer range

yes you can do all this with a conv scope, red dot etc.. the idea is to keep the bullet in a kill zone from a to b with one zero and aiming for the middle.. i suggest shooting it out and make sure it does just that on paper before you go hunting or shtf.

this works on animals hunting etc and most rifles, calibers... your kill zone size and range might change but the idea is the same. you might have to do a little more homework though.

with the given situation... 50/200 is going to lean more tords closer, 36/300 is favoring a longer range.. in most cases its more practical to not push these things to its limits.

 

[Jose]

in most cases its more practical to not push these things to its limits.

Unless you actually shoot your rifle to its max effective range and confirm what the ballistics predictions tell you.

I can tell you that JBM Ballistics is very accurate if you enter a chronographed. It is extremely accurate if your bullet of choice has been tested by Bryan Litz and appears with his empirically derived G7 BC on the list of bullets.

My Howa 1500 shot within 1/2 MOA of the predicted point of impact at 600 yards.

 

[JGreen]

GREAT info all!

 

[Deer_KiLLer]

Unless you actually shoot your rifle to its max effective range and confirm what the ballistics predictions tell you.

I can tell you that JBM Ballistics is very accurate if you enter a chronographed. It is extremely accurate if your bullet of choice has been tested by Bryan Litz and appears with his empirically derived G7 BC on the list of bullets.

My Howa 1500 shot within 1/2 MOA of the predicted point of impact at 600 yards.

you could sight in a couple inches high at 20 yards. and or etc, heck the better you do your math the better your answer. im going to take your example as, your experiance with the accuracy of the ballitics thing you used.

sorry...what i meant by "in most cases its more practical to not push these things to its limits."

as an example... you have a 6" kill zone lets say... well now that we know its 6" lets keep are shots more inside. so lets treat it as a 4" kill zone and zero it for a 4" zone. that will hurt this zeros range a bit but gain better placed shots for the ranges being used...

 

[RichM]

I can't believe that no one has pointed out that the iron sights on an AR have this convenient feature built right into them: they have an elevation knob at the base of the sight that's marked in easy-to-read increments that allows you to zero the rifle at 25m, and then adjust the rear sight for any known distance (or even for any guessed distance).

YMMV.

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