armoredman
Member
Hmm, all this talk is for 5.56mm in an AR platform, no thoughts for an EOTech red dot set up for 7.62x39mm in a vz-58 setup? I actually zeroed at 100 yards, would a 50 work better for me, too?
Took a Carbine Class recently and learned a few things
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Bartholomew Roberts
Member
There is no way someone with a 50yd zero on ANY sight is shooting 6-8" high at close range. They are going to be approximately 2.6" high at very close range due to height over bore. I've shot dozens of optics at close range so I've had plenty of chances to try it. If someone is having that problem, then either the optic or user has a serious problem.
Zak Smith
Member
Here is some 7.62x39 data for different zeros (in yards) and different sight over bore distances
Code:
>> 2.7 SOB
_Bullet_ _BC_ _MV_ 0 50 100 150 200 250 300 350 400 | YARDS
7.62x39 - 25 0.289 2330 > -2.70 2.27 5.44 6.56 5.35 1.51 -5.36 -15.69 -29.96 | drop (inches)
7.62x39 - 50 0.289 2330 > -2.70 0.00 0.89 -0.27 -3.74 -9.87 -19.01 -31.61 -48.16 | drop (inches)
7.62x39 - 100 0.289 2330 > -2.70 -0.45 -0.00 -1.60 -5.53 -12.10 -21.69 -34.73 -51.72 | drop (inches)
>> 2.0 SOB
7.62x39 - 25 0.289 2330 > -2.00 1.57 3.34 3.06 0.45 -4.79 -13.06 -24.79 -40.46 | drop (inches)
7.62x39 - 50 0.289 2330 > -2.00 0.00 0.19 -1.67 -5.84 -12.67 -22.51 -35.81 -53.06 | drop (inches)
7.62x39 - 100 0.289 2330 > -2.00 -0.10 -0.00 -1.95 -6.23 -13.15 -23.09 -36.48 -53.82 | drop (inches)
>> 1.5 SOB
7.62x39 - 25 0.289 2330 > -1.50 1.07 1.84 0.56 -3.05 -9.29 -18.56 -31.29 -47.96 | drop (inches)
7.62x39 - 50 0.289 2330 > -1.50 0.00 -0.31 -2.67 -7.34 -14.67 -25.01 -38.81 -56.56 | drop (inches)
7.62x39 - 100 0.289 2330 > -1.50 0.15 -0.00 -2.20 -6.73 -13.90 -24.09 -37.73 -55.32 | drop (inches)valorius
member
Sounds reasonable to me. The 25/300 worked perfectly fine with a 20.5" weapon. I never shot a carbine on the qualification course, only M-16s.
armoredman
Member
Thanks for the info, Zak. Is that measured bore to middle of sight picture for SOB?
Zak Smith
Member
Bore center to sight center, yes.
benEzra
Moderator Emeritus
The only way to be shooting high at close range would be to zero the rifle extremely close and be shooting further than that distance (say, zero at 3 yards and shoot at 7-10 yards). An Eotech's dot is 2.8" above the bore when looking through the center of the lens, meaning that the worst possible error at close range with a 50-yard zero is 2.8" low, and that only happens within a couple feet of the muzzle. If you are shooting high at close range, then someone must have zeroed the rifle way too close, and such a zero will cause you to miss the target by feet rather than inches at anything other than close range.
Al Thompson
Moderator Emeritus
Or not zero'd at all. Reading a bunch of AARs on carbine classes, apparently getting zero'd on the first day eats lots of time.
benEzra
Moderator Emeritus
To expound a little about zeroing at very close range vs. a 50-yard zero, here's the trajectory for an Eotech on a flattop AR set up for a lower 1/3 cowitness (center of the lens 7.2 cm or 2.8 inches above the bore axis) according to iSnipe, assuming 55gr JHP at 3000 ft/sec:
AR/Eotech, 50-yard zero
AR/Eotech, 10-yard zero
With the 10-yard zero, you are off by 5 inches at 30 yards, two feet at 100 yards, and over four feet high between 230 and 500 yards, making the optic pretty much useless for anything beyond shotgun range without gaining you any precision at CQB distances. Whereas with the 50-yard zero, you are never more than about 2" from the line of sight anywhere from 10 to 250-ish yards, and have much more consistency in the 0-20 yard range.
Even with a 10-yard zero, though, you're nowhere near 6" high at 10-20 yards. To do that, you have to go to something like a 3-yard zero...
...which puts you 6" high at 10 yards. That also means you are over a foot high at 20 yards, 7 feet high at 100 yards, 13 feet high at 200, etc. The round doesn't even return to the line of sight until it is past 1000 yards, subsonic, and falling like a rock.
Having shot a little IPSC/USPSA carbine with an AR/Eotech zeroed at 50 yards, I can vouch for the fact that making precise hits at 3-10 yards with a 50-yard zero is absolutely no problem, and it really makes the optic much more usable at ranges beyond CQB distances.
AR/Eotech, 50-yard zero
AR/Eotech, 10-yard zero
With the 10-yard zero, you are off by 5 inches at 30 yards, two feet at 100 yards, and over four feet high between 230 and 500 yards, making the optic pretty much useless for anything beyond shotgun range without gaining you any precision at CQB distances. Whereas with the 50-yard zero, you are never more than about 2" from the line of sight anywhere from 10 to 250-ish yards, and have much more consistency in the 0-20 yard range.
Even with a 10-yard zero, though, you're nowhere near 6" high at 10-20 yards. To do that, you have to go to something like a 3-yard zero...
...which puts you 6" high at 10 yards. That also means you are over a foot high at 20 yards, 7 feet high at 100 yards, 13 feet high at 200, etc. The round doesn't even return to the line of sight until it is past 1000 yards, subsonic, and falling like a rock.
Having shot a little IPSC/USPSA carbine with an AR/Eotech zeroed at 50 yards, I can vouch for the fact that making precise hits at 3-10 yards with a 50-yard zero is absolutely no problem, and it really makes the optic much more usable at ranges beyond CQB distances.
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Ryder
Member
My EOTech co-witnesses with the irons perfectly.
It's on a 45 carbine. Hits point of aim at all ranges out to 50 yards as near as I can tell so I'm happy with it. I have other rifles for long distance shooting.
It's on a 45 carbine. Hits point of aim at all ranges out to 50 yards as near as I can tell so I'm happy with it. I have other rifles for long distance shooting.
valorius
member
Zak, could you run the ballistics on a 77gr Doubletap OTM round with a 25yd zero for me plz? I have a 'standard height' AR flat top mounted optic. 16" barrel, muzzle velocity is 2700fps. That's the round i have loaded for defense.
Here's a pic of the rifle so you can get a good feel for the height of the optic:
Your best guess should be fine.
Thanks!
Here's a pic of the rifle so you can get a good feel for the height of the optic:
Your best guess should be fine.
Thanks!
HK Dan, just because you shouldn't be worried about a zombie invasion doesn't mean you shouldn't be diligent and prepared in the case of an invasion. Just because it hasn't happened, doesn't mean it can't or won't eventually. Always be ready.
On the topic, I don't have as much experience with this as many of you, but I've always zeroed at 50yds, as my father taught me. It's always worked well for us.
On the topic, I don't have as much experience with this as many of you, but I've always zeroed at 50yds, as my father taught me. It's always worked well for us.
30mag
Member
Shooting in the dark is hard.
Can't see your sights, can't see the target.
Many a rabbit has escaped my Marlin 60 in low-light conditions; not so many escape the 12-gauge.
Do you guys like flashlights? I've heard they provide a target, but better target acquisition. That's an awful trade-off.
Can't see your sights, can't see the target.
Many a rabbit has escaped my Marlin 60 in low-light conditions; not so many escape the 12-gauge.
Do you guys like flashlights? I've heard they provide a target, but better target acquisition. That's an awful trade-off.
Zak Smith
Member
Looks a little higher than a regular ACOG mount so I'll guess 3".
Code:
_Bullet_ _BC_ _MV_ 0 50 100 150 200 250 300 350 400 | YARDS
77gr DT OTM 0.360 2700 > -3.00 2.69 7.07 10.01 11.39 11.02 8.74 4.35 -2.38 | drop (inches)
elevation maxima 11.47" at 215.10valorius
member
I measured it today, it's within +/- .1" of 3", so good guess.
That's not a very pretty trajectory for a MPBR shot from 150-250 yds. Things look up from 300-400 though.
If you wouldn't mind(and if you do, it's fine, i don't want to be a nuisance), can you show me the 50yd zero? (I assume this will very closely approximate a 50m zero? All the ranges in my neck o' the woods are in yards)
The rounds i'm using are a very close approximation of the SOCOM Mk262 Mod1 rounds that were developed for improved terminal ballistics.
That's not a very pretty trajectory for a MPBR shot from 150-250 yds. Things look up from 300-400 though.
If you wouldn't mind(and if you do, it's fine, i don't want to be a nuisance), can you show me the 50yd zero? (I assume this will very closely approximate a 50m zero? All the ranges in my neck o' the woods are in yards)
The rounds i'm using are a very close approximation of the SOCOM Mk262 Mod1 rounds that were developed for improved terminal ballistics.
Zak Smith
Member
50 yard zero
Code:
_Bullet_ _BC_ _MV_ 0 50 100 150 200 250 300 350 400 | YARDS
77gr DT OTM 0.360 2700 > -3.00 0.00 1.69 1.95 0.63 -2.42 -7.38 -14.46 -23.88 | drop (inches)
elevation maxima 2.03" at 133.73valorius
member
Oooooh, that's nice.
Thanks for the help. I definitely need to go rezero at 50. (Though in honesty, if i ever take a shot outside about 10yds in the real world, things have gone way, way, way wrong)
Thanks for the help. I definitely need to go rezero at 50. (Though in honesty, if i ever take a shot outside about 10yds in the real world, things have gone way, way, way wrong)
30mag
Member
valorius
member
From that article:
The immediate kill zone is directly behind the center of the nose.
That's bad information.
The immediate kill zone is directly behind the center of the nose.
A mandated 25-yard zero, in my PD's patrol rifle cert course, resulted in me needing to hold 8-point-something inches low at 100 yards, to hit a desired point of aim; this with a Colt AR15A2 Govt Carbine. If I forgot to hold low, I was likely to totally miss the vital zone of the silhouette target.
A patrol sergeant in my division, with SWAT before his promotion, advised me to re-zero for 50 yards. This meant no need to hold low at long long range, and I became a believer in the 50-yard zero, especially with the 16"-barreled AR15 using iron sights and the carbine-length sight radius. Not that it matters to me, anymore; my eyes started seeing fuzzballs instead of carbine front sights, and I sold my Govt Carbine to a younger officer. (No optics allowed for us, at the time.)
A patrol sergeant in my division, with SWAT before his promotion, advised me to re-zero for 50 yards. This meant no need to hold low at long long range, and I became a believer in the 50-yard zero, especially with the 16"-barreled AR15 using iron sights and the carbine-length sight radius. Not that it matters to me, anymore; my eyes started seeing fuzzballs instead of carbine front sights, and I sold my Govt Carbine to a younger officer. (No optics allowed for us, at the time.)
NCPatrolAR
Member
Having your optic zero'ed at 10 yards and your irons at 100; makes 0 sense. Both should be zero'ed for the same distance so you dont have to remember two sets of holds in the even the optic goes down or you transition to the irons for some reason.
The idea of extremely short zero's for residental use is less than ideal also. Those short zeros might work in limited applications; what happens when you step outside of those applications?
People seem to forget, or just dont know, that inside of 15 yrds you will hit 2.5-2.6" low due to bore-sight relationship.If you want a head shot; aim at the forehead. Hit to the torso? Aim at the notch in the neck. It isnt rocket science.
I kind of wish the instructor was named in the OP so I would know who I need to avoid.
The idea of extremely short zero's for residental use is less than ideal also. Those short zeros might work in limited applications; what happens when you step outside of those applications?
People seem to forget, or just dont know, that inside of 15 yrds you will hit 2.5-2.6" low due to bore-sight relationship.If you want a head shot; aim at the forehead. Hit to the torso? Aim at the notch in the neck. It isnt rocket science.
I kind of wish the instructor was named in the OP so I would know who I need to avoid.
possum
Member
i agree 100% they should be the same, one less thing that you have to think about under stress when time and life is on the line. and if you are only going to use your ar in a "home defense capacity" and you "know" there is no other time that you are going to need and or use it then why would you waste your time zeroing your iron sights at 100yds then. why wouldn't you just zero them at 10yds also( which is still a bad idea for either optic or irons, but that isn't the point i am tryong to make.)
i will expand on this for those that don't know what he means. There is a difference between in height between the center line of bore(imagine a laser going down the barrel) and the center line of sight(imagine a laser going straight out from the optic).there is an article by Pat Rogers in the last SWAT magazine for more info. different optics, mounts, etc will have an effect on offset and that is something that you need to figure out for YOUR gun. the norm is 2.5 or so, but it may be more depending on your mounting solution, height of optic etc.
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Zak Smith
Member
Well, not quite. The bullet rises in what is "almost" a line from its offset at 0 yards to no offset where they meet. Consult the ballistic charts, e.g. those on the first page of this thread, to see the different offset at different distances. If you have a 100 yard zero, there isn't a 2.5" offset at even 50 or 90 yards, which is what your statement says.
possum
Member
Zak,
thank you for the clarification, what i was trying to state and what i wrote were 2 different things, and i failed to articulate it correctly, thank you.
thank you for the clarification, what i was trying to state and what i wrote were 2 different things, and i failed to articulate it correctly, thank you.
I guess you didn't read my post. At no time did I mention that the instructor prescribed a zero for anyone in the class. The talk of zeros arose from my pointing out the low POI at close range with the AR platform. I knew this before ever firing my first shot in class and it was a non-issue for me. The argument over zeros started when people were arguing over how one should zero their AR for defense.
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