If I can get my arse in gear, will post a few trajectory screenshots showing bullet flight path for a few of the zeros used in the video.  If any of them are of particular interest, let me know and will make sure I use those for comparison.  I'll use M855 at 2900 fps as the model cartridge.

If it's all the same, use M2 ball, please!

All of which I understand, and none of which indicates why one zero gives superior grouping to another.

It is more a matter of distance. The farther you are from the target, the bigger your group will be. 1MOA at 100yards = 1 inch. 1MOA at 300 yards = 3 inches. That is under ideal conditions.

Zeroing at distance increases hit probability. A rifle zeroed for 100 yards will have less of a hit probability of hitting a target at 300 yards than a the same rifle zeroed at 300 yards. It is kinda built into the Rear sight of M16A2s/M4s. Ever wonder about the 8/3 (M16A2) or 6/3 (M4) settings on the elevation drum?

All of which I understand, and none of which indicates why one zero gives superior grouping to another.

From experience and from teachings of others, light can affect what we perceive as the target.
"Lights up, sights up; lights down, sights down" especially if I am shooting at bullseye targets which is all I ever shoot.
In the case with lighting conditions, groups will tend to string vertically because the target will appear bigger or smaller. An AllGuard shooter used my databook to demonstrate what he was seeing. The problem was very pronounced at the 600 yard line. I was vertically stringing all the way out to the 7 ring from a COM hold. THe light conditions varied greatly from shadey gray to full sunlight coming from 6 oclock as we were shooting mid day at about noon.

Zero's are definitely a choice of what you purpose is with the rifle, distances and acceptable hit zone sizes.  I prefer the IBZ 50y/200m for my purposes because it has the flatest trajectory and remains within +/- 2.5" all the way out to around ~240yds.  My next preference edged by a hair is the 100.  I will also note that the 100y zero used by Paul Howe is really a modified 100y zero where he purposely offests his 100 yard zero by 3 inches.  So it truly is not a 100y zero unless if you use his hold off technique.

Without trying to explain it some of the ballistic confusion, here is a video that may help.



This is another explanation on the topic by another top trainer especially in the AR/M4/M16 community and former Navy SEAL.

This thread is interesting. I shoot with irons cause can't afford a scope just yet but good to know this info.

I'm curious, does this apply for iron sights as well or only scopes?

This thread is interesting. I shoot with irons cause can't afford a scope just yet but good to know this info.

I'm curious, does this apply for iron sights as well or only scopes?

yes, same

If it's all the same, use M2 ball, please!

A .30 cal round?  Will need BC and velocity of course.

For illumination of why the video had the results he got, standard milspec M855 or M193 are more appropriate as the trajectories will follow the hits he got. 

Ok, here are approximations just to show the variation in bullet strike as a function of zero range.  I used 2.5" sight height above the bore, which I believe is close to AR standard.

Point to observe is the variation in bullet strike above and below line of sight out to max range.  That corresponds to the spread of hits you saw on the video.  Not an exact match, but who knows what he was shooting, as well as differences in his sight height above the bore.  Sorry about the pic size, but it does make it a bit easier to see detail.  The difference the flatter trajectory of the light M193 is interesting if you did switch between rounds without option to re-zero.

Did not post the 200yd zero, as that is essentially the same as a 50yd zero.

25yd:

50yd:

100yd:

300yd:

Point to observe is the variation in bullet strike above and below line of sight out to max range.  That corresponds to the spread of hits you saw on the video.

EUREKA!!  It's using different portions of the curve! 

Ok, guys, was it REALLY that hard for someone just to say "For Pete's sake, Tom, by changing the sighting range, you're rotating the graph of the function?" 

Thanks, robtmc!  Now, I will get you the data for the M2 ball, because I would really love to see how these graphs apply to my collection of WWII battle rifles.

Like I said with the 100 yard zero... pretty much getting like a 6-10" drop at 300 yards.  One point of aim... just below the throat across the chest and you will hit center mass.

M2 ball:
150 gr bullet
.308" diameter
2805 fps at muzzle, 2740 fps @ 78 feet
BC is G8 type, .21
SD is .23

All data courtesy of the internet, and not guaranteed valid!

Can you measure the sight height above bore and say what zero ranges to look at, or the same as before?  Don't want to spam the board with too much stuff.  I am interested in how it compares to 7.62 NATO that I shoot.

Can you measure the sight height above bore and say what zero ranges to look at, or the same as before?  Don't want to spam the board with too much stuff.  I am interested in how it compares to 7.62 NATO that I shoot.

I'll try measure it tonight or tomorrow night, but it's just a blade attached to the barrel.  Certainly less than 1".  And the same zeroes as before would be lovely: 25, 50, 100, 200, 300. 

Mahalo!!

Works for me.  Rear aperture over bolt face is good for height too.  It matters for accurate first crossing of sight line.  AR types are more severe with the large over bore height they have, and optics can make it even more exaggerated. 

I'll swag it at about an inch for iron sights, per what I found for the M1A at around .96 to 1.1".  I can also do listed numbers if you want, maybe email them to you or whatever to avoid clutter.

Paul Howe, who is also pretty beastly, says 100 yard zero.  In his demonstration, you drop the muzzle on target at mid chest /throat... and then at 300 yards you had a 6" drop... hitting still center mass

My point? I think the guns and ammo used here matter - and your mileage may vary.

I have a man-crush on Paul Howe. One old-school bad ass mofo.

Paul Howe is former ODD who was involved in Mogadishu right?

Paul Howe was 1st SFOD-D and was an instructor.  He was also in Somalia and the Battle of Mogadishu in which "Blackhawk Down" was taken from.  He is definitely an old school bad ass and a great guy to train under and just to shoot the shit with over a beer.  He will also tell you that his preferred zero is a loli-pop and not a true zero and comes with some of its own twists that the user should be aware of. 

I have no clue on his history. Just saw him in a few training videos. Loved his no bullshit demeanor.

Louis Awerbuck is another dude that's super badass. Sounds irritated and angry doing the videos.

I have no clue on his history. Just saw him in a few training videos. Loved his no bullshit demeanor.

Louis Awerbuck is another dude that's super badass. Sounds irritated and angry doing the videos.

Louis sounds like a zombie.  Can't tell if he's got a pulse.

Paul Howe was 1st SFOD-D and was an instructor.  He was also in Somalia and the Battle of Mogadishu in which "Blackhawk Down" was taken from.  He is definitely an old school bad ass and a great guy to train under and just to shoot the shit with over a beer.  He will also tell you that his preferred zero is a loli-pop and not a true zero and comes with some of its own twists that the user should be aware of.

Eric Bana's character in the movie Blackhawk Down was based off of Paul Howe.

As far as zero distance goes, I only have 200m to build my range without stepping into the livestock area, which could get me 300m but Id be shooting from the ditch next to the public highway.  200m zero gets my vote.