gents:

if one wishes to have a rifle sighted dead on at 100 yards, then where will the bullet be in relation to the bullseye at 50 yards; high, low?

thanks.

Jeff

if sighted in at 100, with a 1.5" about bore line, the bullet is above LOS at 50 yards

i'll skip the rest of theory tonight .. bullets don't raise, they fall away from line of bore, not to be confused with line of sight

and... the answer is jeffe?

Zero at 100 will be low at 25 and 50 with a 1 1/2 scope to bore relationship.

A 25 yard zero (first intersec) with a 30-06 150 grn hornady interloc bullet at about 2900 fps will be just over an inch high at 50, just under 3" high at 100 and just over 2" at 200 with a drop of nearly 5" at 300. Some where in the 230 to 250ish range would be the second intersec.

quote:

Originally posted by jsl3170:
gents:

if one wishes to have a rifle sighted dead on at 100 yards, then where will the bullet be in relation to the bullseye at 50 yards; high, low?

thanks.

Jeff

A bullet at about 2800 fps that is sighted dead nuts at 100 yards will be approximately .1" above the line of sight at 75 yards, .2" below the line of sight at 50 yards and .7" below the line of sight at 25 yards and 1.5" below the line of sight at the muzzzle.

if zeroed at 100 ..line of sight
zero at 100 with scope is under any less than 25, over from 25 to 100 (or other point of aim) then under from there out

if zeroed at longer range, you get similar results.. basicaly, 25 is the first crossing plain ...

quote:

Originally posted by jeffeosso:
if sighted in at 100, with a 1.5" about bore line, the bullet is above LOS at 50 yards

assuming a normal sight abouve bore, at 50 yards, IF the rifle hits at 25 yards, it will be above line of slight .. howver, be careful, the bullet is NOT rising, itis actually angled up at firing...

generally, at 25 yards, it is crossing the sight plain the first time ... and then whereever it hits the bullet is crossing a second time ... ..

to say it another way ... a bullet, to be on target, has to first pass above the line of sight, then fall below it .. as the bullet is actually angled up at firing.... an is falling the entire time ... the same bullet, fired dead flat, falls from leaving the muzzle.

that confusing enough ...

This is exactly correct. If bullet is dead on, and it needs to be exactly dead on, at 25 yards where is will recross the line of sight again is really a function of the caliber and speed of the bullet. I don't think a blanket statement will get you where you want to go. I would look at JBM ballistic site to figure all this information out for you. It factors in a lot of stuff like Ballistic coefficient, altitude, temperature and wind.

Starting at 25 yards will get you started but the best thing is to check it for sure at 100 yards and ideally at the ranges that you expect to do your shooting at to confirm your calculations.

plug the info here and play with it.....

Or here.

quote:

Originally posted by ted thorn:
Or here.

Interesting.....about the same thing.....

.2" under line of sight at 50 yards!

Sorry jeffe and TEANCUM...

Vapo and Ted have the correct answer to the question.

You're correct that a bullet will cross the LOS twice, but the distance at which it crosses depends on the zero.

If you believe the bullet will be crossing the LOS at 25 yards, you're thinking about the trajectory of a rifle zeroed at about 225-250 yards, dependent on factors like velocity and BC...

Just ran the numbers on BulletFlight to see what scenario would match jeffe and TEANCUM's assertion.

The 155 grain Lapua Scenar zeroed at 100 yards that crosses the LOS at 25 yards, and is high at 50 yards, would have to have a muzzle velocity around 1500 feet per second.

Of course, I don't have any experience with the magic .224" deer-killing varmint bullets. They could be special

quote:

Originally posted by rcamuglia:
Of course, I don't have any experience with the magic .224" deer-killing varmint bullets. They could be special

Yup....those truck spring smashing .224 bullets defy any laws of physics I ever learned!

quote:

Originally posted by rcamuglia:
Sorry jeffe and TEANCUM...

Vapo and Ted have the correct answer to the question.

You're correct that a bullet will cross the LOS twice, but the distance at which it crosses depends on the zero.

If you believe the bullet will be crossing the LOS at 25 yards, you're thinking about the trajectory of a rifle zeroed at about 225-250 yards, dependent on factors like velocity and BC...

There is a special case that I once liked and that was to sight in such that the bullet came up to the line of sight only once and at 2800 fps that distance is about 80 yards. I used to do this to totally eliminate the possibility of ever having to shoot under a target to hit it as the bullet was always under or at the line of sight! In theory it was a good idea but in practice it didn't really do anything for me as I later learned to sight in my rifles at 40 yards and then the bullet was within an inch of the line of sight all the way out to almost 200 yards. I still sight some of my rifles at 40 yards as it keeps a tight rein on trajectory for guns like a .30-06. The bullet crosses the line of sight the second time about 150 yards.

Hey JSL, What have you learned from the responses so far?

The 3 factors that affect the trajectory path are:

a) BC of the bullet (SD/form factor = how aerodynamic)
b) Muzzle Velocity
c) Scope distance above bore

Example - some 7 x 57 mm bullet/load combinations:

175 gr Swift A-Frame bullet @ 2,350 fps - the Bullet's BC = .493
160 gr Swift A-Frame bullet @ 2,500 fps - the Bullet's BC = .450
140 gr Swift A-Frame bullet @ 2,700 fps - the Bullet's BC = .335

The inter-play of an increased velocity and a worsening BC has a cancelling effect on each other.
By changing the form factor or sleekness of the bullet the BC can obviously be improved.
The heavier bullet has a higher sectional density (SD), and generally will yield a higher BC
as can be seen in this example in the same caliber with the same type of bullet.

Let us assume:

a 100 yds zero setting with a scope bore of 1.5" above the barrel's bore.

The results are:

Trajectory --------------------- Crossing LOS ----- 50 yds ---- 100 yds ----- 150 yds
175 gr Swift A-Frame --------- 45 yds ----------- +0.1" -------- 0 ------------- -1.9"
160 gr Swift A-Frame --------- 50 yds ------------ 0 ------------ 0 ------------- -1.7"
140 gr Swift A-Frame --------- 60 yds ----------- +0.1" -------- 0 ------------- -1.4"

Warrior

quote:

The results are:

Trajectory --------------------- Crossing LOS ----- 50 yds ---- 100 yds ----- 150 yds
175 gr Swift A-Frame --------- 45 yds ----------- +0.1" -------- 0 ------------- -1.9"
160 gr Swift A-Frame --------- 50 yds ------------ 0 ------------ 0 ------------- -1.7"
140 gr Swift A-Frame --------- 60 yds ----------- +0.1" -------- 0 ------------- -1.4"

Warrior,
I think there's an error in the last row.....the bullet cannot cross the line of sight at 60 yards, then be +.1" at 50 and 0.0 at 100.....I think the "+" sign is in error and should be a "-" sign....check it again.

In all practicality it makes little difference as a tenth of an inch almost don't exist at 50 yards in the real world of shooting.....

Thanks vapodog, that was a typo - s/be -0.1"

Warrior

quote:

Originally posted by jsl3170:
gents:

if one wishes to have a rifle sighted dead on at 100 yards, then where will the bullet be in relation to the bullseye at 50 yards; high, low?

thanks.

Jeff

Jeff,
I usually just bore sight it (if bolt rifle) at 50 ysrds, shoot it and adjust dead on. Then move to 100 and make the final adjustments needed.

**AND NOW, THE FINAL, DEFINITIVE WORD ON THE SUBJECT FROM OUR RESIDENT BALLISTICIAN****






***********FOSTER JEFFEOSSO BROOKS******************

quote:

Originally posted by jeffeosso:
if sighted in at 100, with a 1.5" about bore line, the bullet is above LOS at 50 yards

assuming a normal sight abouve bore, at 50 yards, BELLLLCH, HICCUP...IF the rifle hits at 25 yards, it will be above line of slight .. howver, HIC... be careful, the bullet is NOT rising, itis actually angled up at firing... ROLLING BELCH
generally, at 25 yards, it is crossing the sight plain the first time ... HIC.... and then whereever it hits the bullet is crossing a second time ... ..BURP
to say it another way ... a bullet, to be on target, has to first pass above the line of sight, then fall below it .. as the bullet is actually angled up at firing....HIC... an is falling the entire time ... the same bullet, fired dead flat, falls from leaving the muzzle.


that confusing enough ...RAALLLPH!...

rcamuglia, I think if you trace your ancestry back far enough, you'll find that you're related to Hot Core!.....at least a little bit......

Here is a Novel Idea...

Sight in your gun at 100 yards, and then SHOOT it at 50.

You might be suopprized.

I have seen 8 identical rifles, all with "100 yard" zeros shot at 25, 50, and 75 yards.

In the "real world" each one of them shot a little different.....

Why??? Because most rifles really do not have a "perfect" 100 yard zero.

So mathamatical ballistics aside, if it "ain't perfect" at 100, it will not be "perfect" anywhere else either...

So you will have to actually shoot the rifle to be sure.

Ha!

No harm or offence intended!

Just good, clean fun!

I bet just about everyone has posted plastered!

At this point I'll throw out my "20824" rule....

I find that many common big game rifles that shoot at velocities at 2700-2800 FPS will fit the "20824" pattern.....

The thing about it is that 20824 is easy to remember.....2X4=8....4+2+2=8....it's just an easy number to remember and it's a big help in big game hunting...

Here's what it means:
2= 2" high at 100 yards
0= dead on at 200 yards
8= 8" low at 300 yards
2= 2' low at 400 yards
4= 4' low at 500 yards

and this seems to be good data for a lot of rifles!....308, .30-06, .270 Win, .280 Rem, and a lot more.....even my .35 whelen!!!

Now all you need is a way to determine range of the target.....

Depth of a bull elk is about 24" and depth of a nice buck is about 18"....so if your elk is 400 yards out then hold over 1/2 elk depth.... if the elk is at 300 yards then hold just under the back a few inches.....it gets easy to judge when these numbers are used.....

quote:

Originally posted by vapodog:
At this point I'll throw out my "20824" rule....

I find that many common big game rifles that shoot at velocities at 2700-2800 FPS will fit the "20824" pattern.....

The thing about it is that 20824 is easy to remember.....2X4=8....4+2+2=8....it's just an easy number to remember and it's a big help in big game hunting...

Here's what it means:
2= 2" high at 100 yards
0= dead on at 200 yards
8= 8" low at 300 yards
2= 2' low at 400 yards
4= 4' low at 500 yards

and this seems to be good data for a lot of rifles!....308, .30-06, .270 Win, .280 Rem, and a lot more.....even my .35 whelen!!!

Now all you need is a way to determine range of the target.....

Depth of a bull elk is about 24" and depth of a nice buck is about 18"....so if your elk is 400 yards out then hold over 1/2 elk depth.... if the elk is at 300 yards then hold just under the back a few inches.....it gets easy to judge when these numbers are used.....

Seriously, just poking fun.

quote:

.. and no, i was plastered ..

quote:

though i'd be happy to have a beer with you ... or go shooting with you ...

Likewise! There's no doubt in my mind that most of us here would have a great time together since we share the same passions, no matter what we disagree on!

Where'd your post go jeffe?

quote:

Originally posted by vapodog:
At this point I'll throw out my "20824" rule....
..

Nice and real close to reality!

Strange thing is that just last Friday I was showing a fellow something quite similar to that about the 30-06 with 125gr Sierra Bullets, 125gr Nosler B-Tips, 150gr SPBT Speers and 165gr Nosler B-Tips. Once a person spends some time in the External Ballistic Tables, it helps select a realistic, somewhat Standard Trajectory that can be used with multiple rifles. It is generally as easy as picking the right Bullets(which hopefully the rifle likes) and adjusting the Charge slightly so they Fly as close as possible to the Standard Trajectory of your choice.

I do not remember anyone discussing that before here on the Board, or perhaps I just forgot about it. Anyway, it is an absolutely excellent point that you brought up Vapo.

That way when you tote a rifle all year shooting Varmints, stray Dogs, whatever, at random distances, the Trajectory which is being Imprinted on your Synaptic Computer will also match the Trajectory for the rifle you will use when Hunting.

The "20824" rule was an accidental discovery about a year ago.....it's always been there but It wasn't until then that I was able to see it....

Among the reasons my .35 Whelen shoots 225 grain bullets is because I want it to conform to that trajectory.....or at least close.....I'd have backed down to less bullet to make that happen....

An inch or two difference is inconsequential for the most part.....we are all doing a lot of estimating in the field and besides....even a nice buck is a pretty big target if it's standing still and allows you a decent rest!

Best of all is the number of cartridges that conform closely to this rule.....almost any big game round will handle a bullet at 2700-2800 FPS and this includes the .375 H&H all the way to the .257 Roberts.....just pick the bullet to match.

http://www.jacksonrifles.com/ballistics.htm

this is a link to a ballistics spreadsheet in Excel format, you can take a laptop with you or work things out when you are offline and it's not to bad.

I used to tape the drop in my scope cap but like the others have said, one eventually learns them by heart.

Remember that scope height above the centre line of the bore is a very important parameter for the calculation you're interested in.

Regards,

GH

PS. Loving the smiley, it's really found a home on here...

Wow, I understand that Dell is making a camo laptop for all you techies to take to the woods with you. Excellent asset to go along with your wind thingy, and your how far away thingy, and your shooting sticks, and you gsp, and, of course, your cell phone. Then you wouldn't have to walk around with those pieces of paper taped to the side of your stock.

Back in the dark ages, Jack O wrote an article about the path of a bullet and he, IIRC, said the bullet crossed LOS at 37 yards to hit dead on at 100. Since then whenever I put a new scope on, I begin my shooting @35-40 yards. When I aim at a bullet hole and the shot hits it, I move out to 1oo yards. Then my shots, regardless of calibre nor veleocity, are close enough to make a minor adjustment to put them where I want them.
To answer the question directly, at 50 yards the bullet would be above LOS. That is to say, if your rifle is sighted in to hit point of aim at 100 yards and you moved the target in to 50 yards, the bullet would strike above the bull. (and that's no bull. )

Go to the Norma ballistic software site below and click "define your own" and play around with various velocities, etc. Its quite interesting.

http://www.norma.cc/javapage_US2.asp?Lang=2

Be sure and give it time to load the program.

I think you'll find that where the bullet is in reference to the LOS at 50 yds will depend on the bullet, velocity, etc.

Where have you been hiding wasbeeman!

quote:

Originally posted by wasbeeman:

Back in the dark ages, Jack O wrote an article about the path of a bullet and he, IIRC, Obviously you don't remember correctly It's just not true!

said the bullet crossed LOS at 37 yards to hit dead on at 100 200 maybe . Since then whenever I put a new scope on, I begin my shooting @35-40 yards. When I aim at a bullet hole and the shot hits it, I move out to 1oo yards. Then my shots, regardless of calibre nor veleocity, are close enough to make a minor adjustment to put them where I want them.
To answer the question directly, at 50 yards the bullet would be above LOS. That is to say, if your rifle is sighted in to hit point of aim at 100 yards and you moved the target in to 50 yards, the bullet would strike above the bull. (and that's no bull. )

To the last bolded statement.....

quote:

Originally posted by rcamuglia:
Where have you been hiding wasbeeman!

He should have stayed hiding.....He's sucking on the sauce again!

You're right Vapo.

I wonder why so many are confused by this?

If you set the zero (the definition of where a bullet crosses the LOS, for the confused) at 37 yards, it's on (zeroed) at 240 ....

quote:

Originally posted by rcamuglia:
If you set the zero (the definition of where a bullet crosses the LOS, for the confused) at 37 yards, it's on (zeroed) at 240 ....

....or a little less if the bullet is a liberal....

quote:

Originally posted by rcamuglia:
If you set the zero (the definition of where a bullet crosses the LOS, for the confused) at 37 yards, it's on (zeroed) at 240 ....

My "out west rifles" are sighted for just that. Both are nearly 3" high at 100 and zero'sh around 230/240.
They are a 270 WSM and 7 Mag

Those are real shooting numbers by the way....not pc generated