Thoughts?

What distance do you choose to zero your rifle in at?

dubya

Thoughts?

dubya

Yeah, I wonder what shirt Travis is wearing.

Yeah, I wonder what shirt Travis is wearing.

personally, i was wondering what type of ammo he was using, but it's great to see that there are those among the forum-dwellers who are fashion-conscious, as well!

joo rook mahvaleous, dahling!

First thought: Damn, that bugger can SHOOT!  Second thought: I never thought about different zero ranges, but I'm now a firm believer in the 300 yard zero.  I don't know why anyone would use anything different, honestly.  The exact same hold from touching distance out to three hundred, and all of the POIs are within a four inch circle?  Too good to be true!  Too bad here on Oahu we don't have a long enough range to do it, so I guess I'll have to settle for zeroing at 100 yards and then adding in whatever the old iPhone ballistic calculator app says I need for 300. 

joo rook mahvaleous, dahling!

That's...Incredible!

I'm now a firm believer in the 300 yard zero.  I don't know why anyone would use anything different, honestly.  The exact same hold from touching distance out to three hundred, and all of the POIs are within a four inch circle?  Too good to be true!  Too bad here on Oahu we don't have a long enough range to do it, so I guess I'll have to settle for zeroing at 100 yards and then adding in whatever the old iPhone ballistic calculator app says I need for 300. 

We shoot the 200, 300 and 600 yardlines at least once a month at Puuloa.

Thoughts?

What distance do you choose to zero your rifle in at?

My thoughts are that this just doesn't make sense.  The physics governing the flight of a projectile don't change because of where you point the barrel! 

I mean, I get that it has to do with an expanding cone; more to the point, a cone that converges at the muzzle.  But if a bullet drops 4" as it travels from 300 to 400 yards, then it drops 4" every time it makes that trip!  The fact that I point the barrel 1 degree higher shouldn't change that.

It makes my head hurt.

That being said, I zero my high-powered rifles at 100 yards.  Why?  Because Kokohead is where I can shoot regularly, and 100 yards is the farthest place I can easily place a target frame.  When I took Chuck Taylor's sniper class, he was a proponent of the 200 yards zero, and the rifle I used for that class I did zero at 200. 

My carbines and .22 rifles are a different story.  Those I tend to zero at 50 yards, for nearly the same reason. 

Thoughts?

What distance do you choose to zero your rifle in at?

dubya

100 yards but like I learned from the All Guard team, zeroes are just a baseline; it will change given conditions.
With that in mind I know how much clicks I am up from my mechanical zero. I guess the best analogy is driving a stick shift. At about xx mph you shift into the next gear but it all depends on whether you are climbing a hill etc. Knowing where you are (range estimation) in relation to your mech zero is important. For example my AR service rifle zeros are 1 MOA from mech zero for 100 yards, 3 MOA up for 200, 4.5 MOA for 300 and 18.75 MOA up for 600. given that I am shooting 77s at about 2700 fps from 100-300 yards and 80s at 2700 fps at 600. If I shoot 77s all the way to 600 my zero is about 4-5 MOA less than shooting with 80s.

My thoughts are that this just doesn't make sense.  The physics governing the flight of a projectile don't change because of where you point the barrel! 

I mean, I get that it has to do with an expanding cone; more to the point, a cone that converges at the muzzle.  But if a bullet drops 4" as it travels from 300 to 400 yards, then it drops 4" every time it makes that trip!  The fact that I point the barrel 1 degree higher shouldn't change that.

It makes my head hurt.

That being said, I zero my high-powered rifles at 100 yards.  Why?  Because Kokohead is where I can shoot regularly, and 100 yards is the farthest place I can easily place a target frame.  When I took Chuck Taylor's sniper class, he was a proponent of the 200 yards zero, and the rifle I used for that class I did zero at 200. 

My carbines and .22 rifles are a different story.  Those I tend to zero at 50 yards, for nearly the same reason.

The physics don't change but where your bullet impacts will if you change the direction of your barrel. A one degree offset will affect the bullet's final resting place.
The sights are what we use to perceive where the barrel and ultimately where the bullet will land. We use line of sight which in relation to how a bullet travels is somewhat misleading because gravity will affect the bullet the moment it leaves the barrel and it will drop at a constant rate no matter what velocity.  Our line of sight in a straight line versus an arc of the bullet. IMHO, knowing your rifle, ammo and how to adjust your sights in relation to a particular range is important. Travis conducted a very good experiment and it I think ultimately it bestows on your experience with your rifle, equipment and ammunition. In addition, shooting in different environments and ranges will help you determine what zero you should set your rifle at. Of course, if you are in the mil or other similar orgs, I'm not saying you should "Do wateva u like"

A one degree offset will affect the bullet's final resting place.

Right, and obvious.  Let's do a "what if"

You put your rifle in a vise, and align it parallel to the ground.  Then, using a delicate digital level, you incline it 5 degrees.  you fire a round.  A sophisticated tracking system records the flight of the projectile.  it notes, amongst all the other data it records, that between the distances of 400 and 500 yards, the bulled drops exactly 4", from a height of 6' to 5'8".

Now you increase the tilt by 1 degree, to 6 degrees above horizontal.  You fire again.  Obviously the point of impact changes at virtually every point along the flight path.  But between 400 and 500 yards, the bullet will still fall by about 4".  Not exactly, but pretty close.  Admittedly that drop is now happening at a different height, let's say from 7' to 6"8(ish)". 

Right?

So why doesn't that matter?

My thoughts are that this just doesn't make sense.  The physics governing the flight of a projectile don't change because of where you point the barrel! 

I mean, I get that it has to do with an expanding cone; more to the point, a cone that converges at the muzzle.  But if a bullet drops 4" as it travels from 300 to 400 yards, then it drops 4" every time it makes that trip!  The fact that I point the barrel 1 degree higher shouldn't change that.

It makes my head hurt.

That being said, I zero my high-powered rifles at 100 yards.  Why?  Because Kokohead is where I can shoot regularly, and 100 yards is the farthest place I can easily place a target frame.  When I took Chuck Taylor's sniper class, he was a proponent of the 200 yards zero, and the rifle I used for that class I did zero at 200. 

My carbines and .22 rifles are a different story.  Those I tend to zero at 50 yards, for nearly the same reason.

You are not correct, the bullet flight does change depending on where the barrel is pointed.  What Travis is talking about is where you set your crosshairs or dot.  Depending on where you set your dot along that flight path of the bullet will give you different results.

For instance a lot of hunters will set their crosshairs at 200 yards.  This means that given a relatively flat shooting bullet if they hold on the vitals of the animal they will hit it..............it may be a bit high or low, but you will hit it.  It makes distance estimation a lot less important.  Same reason (flat shooting round) is why a lot of deer hunters like a 0.270 instead of a 0.308.

Now what you need to realize is that not all bullets will drop at the same rate vertically versus how far they have traveled horizontally.  There is a term called a BC or ballistic coefficient.  This is a measured factor that indicates how "efficient" a bullet is..............in other words how well does the bullet keep velocity.  The longer it takes for a bullet to travel a certain distance (in general) the further it drops vertically.



Now back to the drop.  The problem is when you start to get into extreme angles your bullet point of impact is changed because gravity is acting in a direction that is far from perpendicular to the path of the bullet and more parallel to it. 

Right, and obvious.  Let's do a "what if"
You put your rifle in a vise, and align it parallel to the ground.  Then, using a delicate digital level, you incline it 5 degrees.  you fire a round.  A sophisticated tracking system records the flight of the projectile.  it notes, amongst all the other data it records, that between the distances of 400 and 500 yards, the bulled drops exactly 4", from a height of 6' to 5'8".
Now you increase the tilt by 1 degree, to 6 degrees above horizontal.  You fire again.  Obviously the point of impact changes at virtually every point along the flight path.  But between 400 and 500 yards, the bullet will still fall by about 4".  Not exactly, but pretty close.  Admittedly that drop is now happening at a different height, let's say from 7' to 6"8(ish)". 
Right?
So why doesn't that matter?

Yes, physics will dictate that the bullet will drop the same distance no matter how you point your barrel; what I stated is that POI will change given the different elevation of the barrel. Not arguing with you or physics.

Right, and obvious.  Let's do a "what if"

You put your rifle in a vise, and align it parallel to the ground.  Then, using a delicate digital level, you incline it 5 degrees.  you fire a round.  A sophisticated tracking system records the flight of the projectile.  it notes, amongst all the other data it records, that between the distances of 400 and 500 yards, the bulled drops exactly 4", from a height of 6' to 5'8".

Now you increase the tilt by 1 degree, to 6 degrees above horizontal.  You fire again.  Obviously the point of impact changes at virtually every point along the flight path.  But between 400 and 500 yards, the bullet will still fall by about 4".  Not exactly, but pretty close.  Admittedly that drop is now happening at a different height, let's say from 7' to 6"8(ish)". 

Right?

So why doesn't that matter?

It does matter, and you're hitting the nail on the head without realizing it.  The problem is that your target is, say, 6'0" tall.  The first bullet dropped the four inches down to 5'8" and hit him in the forehead.  The second bullet goes 8" over his head.  The flight path of the bullet relative to the line of the bore was relatively similar, but there was a big difference in the point of impact for the two rounds.  I do think the initial bore angle would make a difference on the arc of the bullet, which is why you have to account for the angle of the shot in long range shooting, right? 

Anyway, the big takeaway is that, like you said, changing the initial angle of your barrel will change the point of impact of your bullet.  The trick is to find the right zero range (initial angle of the bore) for your rifle and round in order to maximize your chances of scoring a hit.

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.

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

Of course the gun/ammo are the key.  Just recall when the military went to the 5.56 varmint round with the flat trajectory.  Early M-16s did not even have a freaking elevation adjustment other than the coarse front sight post.  Just flip the back sight for close or far (I have to wonder how often that got used), and let the minimal drop over usual engagement range take care of the rest.

Thank the Marines and emphasis on real marksmanship for forcing the return of true adjustable rear sights, not that many know how to use them in these days of optics.  With the new popularity of heavier cartridges, shooters are becoming familiar with trajectories again.  Great fun looking at graphs of bullet drop when zeroed at various ranges to see effective hit zones.  I found some great freeware called "Ballistics Tables"  some time back that lets you plug in all sorts of details to figure this out, like sight height over the bore and all.  Wish I had a chrono for accurate velocity inputs.  Good stuff.

Addendum:  One huge benefit of the software I mentioned with the sight height input is the ability to see the first bullet crossing distance.  Depending on cartridge, like 30 yds before dropping to the zero range at 300.  I have a laser reflective piece of tape 26 yds out for setting sights.

Piece of cake to sight in with a laser boresighter and be on the paper at the desired range when first shooting.  I have found some small variances, but so far, inches, due to recoil and whatnot.  Still, superior to shooting all over the place trying to get on the paper.  Works for iron and optic sights, just adjust where the dot hits by an inch or two per what the software trajectory predicts.

On a sort-of related note, I read an interesting article about using your mildots for ranging.  It emphasized the importance of knowing your bullet drops, because you can use mildots to get an accurate shot off at an unknown range without measuring and doing math if you do.  For example, you look at a target and guess it's somewhere between 250-400 yards.  (Because you suck at guessing range, that's why.  This is a hypothetical, dammit!   )  You know that your POI will be one mil low at 200, and four mils low at 400.  The target measures a shade over three mils on the reticle, so you put the first dot at the top of the target and let 'er rip.  You know you're going to be on for range because the target covers all POIs from 200-400 yards. 

Just thought was a neat point; I've never used a mildot scope, but I'm planning to buy one for my AR once I get my pennies scraped together, so I've been doing some reading on how best to employ them.

Ok, I went camping this weekend, and was discussing this post with another forum member and personal friend who was there.  And I think I am not doing a good job of expressing my confusion.  So let me try again...

First, I get the forces involved.  I understand gravity, ballistic coefficient, air density, and flavor of chewing gum all have impact on the flight path.  I also get that small changes at the beginning make large changes at the end.

I may get the details slightly off because I'm not willing to invest another 8 minutes rewatching the video just now, but this fellow Travis has a series of targets (let's say 6).  He shoots each of these targets multiple times, one time each at 25, 50, 100, 200, 300 and 400 yards.  That's a total of 36 shots.  For each and every one of those 36 shots, he uses the same sight picture.

Now, between targets, he changes the sighting of the rifle.  The first target is shot at all distances with a zero of 25 yards.  The second, shot at all distances with a zero of 50 yards.  Etc, etc.

It's obvious that the holes in each target are going to differ. 

The part that I just refuse to believe is that, on one target, the best grouping is 3 shots in one hand span, while on another target, the best grouping is 5 shots in one hand span, and that difference is attributed to differing zeros. 

In my mind, the vertical string shouldn't change all that much.  It should appear higher or lower on the target, yes.  But the bullet should fall about the same distance as it traverses the distance between distance X and distance Y.  Not exactly the same, because the trajectory is slightly different, but the end result should not be (in my brain) that any variation in zero should change group sizes at any distance.

I'm not denying that it seems to work.  Some fairly respectable organizations seem to believe in it. 

I'm just saying that it CAN'T work.

Ok, I went camping this weekend, and was discussing this post with another forum member and personal friend who was there.  And I think I am not doing a good job of expressing my confusion.  So let me try again...

First, I get the forces involved.  I understand gravity, ballistic coefficient, air density, and flavor of chewing gum all have impact on the flight path.  I also get that small changes at the beginning make large changes at the end.

I may get the details slightly off because I'm not willing to invest another 8 minutes rewatching the video just now, but this fellow Travis has a series of targets (let's say 6).  He shoots each of these targets multiple times, one time each at 25, 50, 100, 200, 300 and 400 yards.  That's a total of 36 shots.  For each and every one of those 36 shots, he uses the same sight picture.

Now, between targets, he changes the sighting of the rifle.  The first target is shot at all distances with a zero of 25 yards.  The second, shot at all distances with a zero of 50 yards.  Etc, etc.

It's obvious that the holes in each target are going to differ. 

The part that I just refuse to believe is that, on one target, the best grouping is 3 shots in one hand span, while on another target, the best grouping is 5 shots in one hand span, and that difference is attributed to differing zeros. 

In my mind, the vertical string shouldn't change all that much.  It should appear higher or lower on the target, yes.  But the bullet should fall about the same distance as it traverses the distance between distance X and distance Y.  Not exactly the same, because the trajectory is slightly different, but the end result should not be (in my brain) that any variation in zero should change group sizes at any distance.

I'm not denying that it seems to work.  Some fairly respectable organizations seem to believe in it. 

I'm just saying that it CAN'T work.

The best thing to do to understand zeroes for different distances is to get out there and shoot at varying distances. The bullet does not travel in a straight line. It travels in an arc. In relation to the sights on the gun, the barrel will be pointed up/down or parallel to the ground. The bullet will fall at a constant rate, that's a given, due to gravity. Remember that while we look through the sights to acquire a target and point the barrel to it, the bullet does not travel as our line of sight does; that's why at certain distances the bullet will cross the sights line at two points which may give the impression that the bullet "flies & rises" through the air. That's what drill sergeants said to us in basic. Of course we never argued.
So in summary, we have a straight line (sights) and an arc (bullet path) that intersects to give us a reference point as to where our bullet will impact.

The part that I just refuse to believe is that, on one target, the best grouping is 3 shots in one hand span, while on another target, the best grouping is 5 shots in one hand span, and that difference is attributed to differing zeros.

I'm just saying that it CAN'T work.

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.

The best thing to do to understand zeroes for different distances is to get out there and shoot at varying distances. The bullet does not travel in a straight line. It travels in an arc. In relation to the sights on the gun, the barrel will be pointed up/down or parallel to the ground. The bullet will fall at a constant rate, that's a given, due to gravity. Remember that while we look through the sights to acquire a target and point the barrel to it, the bullet does not travel as our line of sight does; that's why at certain distances the bullet will cross the sights line at two points which may give the impression that the bullet "flies & rises" through the air. That's what drill sergeants said to us in basic. Of course we never argued.
So in summary, we have a straight line (sights) and an arc (bullet path) that intersects to give us a reference point as to where our bullet will impact.

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