The question relates to the Point-of-Impact movement as the Velocity increases in a firearm. For this exercise, we will consider 4 different 30cal cartridges at 4 different distances.

Feel free to give different examples. Just let us know what the distance is and the cartridge of your choice.

No cheating with a Ballistics Calculator. Base your answer on previous experience with the cartridge you are the most familiar with. This is not an exercise to "look up" an answer.

Question:
A 30-30Win with a 150gr RN, 2200fps->2400fps with the Target at 100yds.

Choices:
1. Up
2. Down
3. May do either
4. Don't know

Question:
A 308Win with a 150gr BTSP, 2600fps->2800fps with the Target at 200yds.

Choices:
5. Up
6. Down
7. May do either
8. Don't know

Question:
A 30-06 with a 165gr BTSP, 2700fps->2900fps with the Target at 300yds.

Choices:
9. Up
10. Down
11. May do either
12. Don't know

Question:
A 300WinMag with a 180gr BTSP, 2900fps->3100fps with the Target at 400yds.

Choices:
13. Up
14. Down
15. May do either
16. Don't know

 

I didn't vote because I have no experience w/ those calibers listed.

I can relate my experience with the following:

• 6" 357 revolver - It will shoot higher at 25yds as the bullet weight increases from 125 to 158 grs with the same velocity. However, I can bump the velocity up on the 125s to shoot same POI as the 158s.
  
• Scoped 270 rifle - No change in POI at 100 yds w/ either the velocity changes (2750 to 3100) or bullet wt. changes (130, 135, 140, 150).
  
• Scoped 7.5x55 rifle - It will shoot higher at 100 yds as the bullet wt. changes from 165 to 180 grs.
  
• Scoped 8x57 rifle - It will shoot higher at 100 yds as the bullet wt. changes from 185 to 200 grs.
  

Is the 30-30 iron sights?

The other rifles are scoped I assume, with a sight hight of 1.5 to 1.7 and at least a 22" tube???

Iv'e often wondered about this. For me, things seem to change around 2500fps. I have a 45-70, .348 winchester, 9.3x 74, two .350 rem. mags, a .35 whelen, and a 7mm-08 that all shoot higher as velocity goes up, when I'm working under 2500 fps. Then, when the .350 rem. mag., 7mm-08,two .270 wins, 338-06,30-06, 250-3000, are being worked up in the 2600 to 3000 fps. range, they shoot lower as the velocity goes up. What really drives me nuts ( and mabey this is another thread) Is when I work up a load out of one of the reloading manuales, and I get a vertical string, each bullet hitting just a bit higher, or lower, as the case may be. But, no bullet being more than a caliber width left or right from the center line. Then, I come back with five rounds, at any load density, and they are all over the paper?

gravity is constant.... the bullet drops from the time it leaves the muzzle unless the sights or scope is compensating for aiming point on the target.......

quote:

Originally posted by tasco 74:
gravity is constant.... the bullet drops from the time it leaves the muzzle unless the sights or scope is compensating for aiming point on the target.......

Bingo baby....and loosing energy the mila-second it leaves the barrel. The only rise is created by the sighting plane. That is highly variable.

quote:

Originally posted by ted thorn:
Bingo baby....and loosing energy the mila-second it leaves the barrel. The only rise is created by the sighting plane. That is highly variable.

Also seems recoil and vibration (and possibly time in barrel) plays a part as to where the barrel is pointing when the bullet exits!

A bullet (any grns.) set loose on a flat plane will only fall no matter what the FPS

The same bullet dropped from tweezers from the exact same plane at the exact same time the above bullet is fired will impact the ground a the exact same time.

Gravity is constant.

When the bullet weight or powder quantity increases or decreases the barrel vibrations change. Each rifle is different, so the only way to know what a rifle will do is shoot it off a bench rest.

quote:

Originally posted by ted thorn:
Is the 30-30 iron sights?

The other rifles are scoped I assume, with a sight hight of 1.5 to 1.7 and at least a 22" tube???

Good questions Ted. Use whatever you desire.

I was thinking about this earlier and thought I should have included where each rifle was "Zeroed". But a lot of us Zero at different distances, so that would have put restrictions on folks they normally do not have.
-----

Hey Ray, Feel free to vote what you think would happen based on your other cartridges. The wide spread of selections I see this morning could result in some good discussions.

Why do you think the 270Wins POI remains about the same with both changes in Velocity and Bullet weight?

What do you think causes the Heavier Bullets in the 7.5x55 and 8x57 to Increase the POI?
-----

Gravity is constant! Hey Ted and Tasco74, Are you all saying an Increase in Velocity has no effect on the POI? That it all has to do where it is Sighted-In?

Hot Core ----- Just about when I think I have it figured out, then a group will do something I had not counted on. I have seen groups go lower with more velocity, sideways or way up. I think each barrel has it's own personality. The harmonics between the bullet and speed just have to be discovered by lots of shooting and chart work. I worked all summer getting my two .270 WSM's to print groups at the same POI with different weight bullets. I can now trust that the 130 and 150 grainers will print where I want them when I pull the trigger, regardless of whether I have a Deer load or Elk load. By the way, it took two different powders to do the trick. Just my .02's. Good shooting.

`

Actually..
If zeroed for the lower speed, same bullet weight, a faster load will hit LOWER

if zeroed for same speed, heavier bullet, the heavier bullet will hit HIGHER

if bullet weight goes up, and velocity goes up, its a crap shoot, but i bet it could be solved by math...

Why?

Simple .. dwell time in rotation.

Let SAY thay it takes .01 second for a 2400fps bullet to exit the barrel. From the instant of primer strike to the bullet leaving, the barrel is LIFTING (moving in path of least resistance) increasing the angle of the barrel at the release point.

A fast bullet leaves at SAY .009, meaning the bullet leaves the barrel LOWER than the slower bullet


With a heavier bullet, the recoil raise the barrel MORE in the same time, resulting in a higher release point

if you combine them, there's a point where its not faster ENOUGH to exit the barrel fast enough to not raise or lower ..

Grenadier, your math is correct, except you DO change the launch angle by the dwell time of the rifle in recoil


Therefore, faster load, hits lower .. heavier bullet, same speed, hit higher, ... toss up if you are changing to heavier bullet and faster speed...

Want to prove this for yourself? Load a 30 sometime with 120gr bullets at 2200, 2500, 2800 fps .. and sight in for the 2500 load ... ***I HAVE*** as i was appalled one day that my 120gr 257 bullets hit MUCH higher than my 85gr loads .. and i had just chronoed them, knowing the 85s were much faster, but the 120 hit much higher... heavier AND slower bullets hit much higher

have repeated with 300 win, 458 AR, and 45LC, at will ..

quote:

Originally posted by Hot Core:
Gravity is constant! Hey Ted and Tasco74, Are you all saying an Increase in Velocity has no effect on the POI? That it all has to do where it is Sighted-In?

Yes gravity is constant no matter the speed. An increase in velocity will get your bullet to the target faster
(this may explaine POI change) but it will not help in any way the effects of gravity.
I can say nothing on barral harmonics and don't even want to go there.

btw, it is a MISNOMER that a bullet dropped at the muzzle will hit the ground at the same time ..

condition must be, with the bore perfectly aligned with the ground, and immobile, a bullet dropped from the bore height will hit the ground at the same time ..

however, a rifle sighted in for 100 yards is angled UP and will hit the ground slightly later ..

yes, just accept it .. the bullet arcs ABOVE the line of sight/bore due to angle convergence of the sights and bore.

which is why a rifle hits about the same POI at 25 and 100 yards

For the sake of argument, we can say that barrel harmonics will introduce a certain amount of variability to the question.

If you discount this, a bullet's trajectory (an arc) will coincide with aim (a vector) exactly twice. Once on the way up, another on the way down.

When you increase the velocity of a bullet, you change where these coincident points on the arc are (as the arc is elongated), as well as changing its apex.

The change in point of impact will change, depending on where you zeroed your rifle, and where this is relative to your new bullet arc.

-nosualc

quote:

When the bullet weight or powder quantity increases or decreases the barrel vibrations change. Each rifle is different, so the only way to know what a rifle will do is shoot it off a bench rest.

The British SMLE in 303 (not the No4) had an unusual compensation characteristic in fact. The harmonics were such that it grouped better at long distance than did the No4.

As explained it was by fluke "just right" so low velocity rounds and high velocity rounds exited the barrel at just the right point to cause a smaller group.

quote:

Originally posted by Grenadier:

quote:

Originally posted by jeffeosso:
Grenadier, your math is correct, except you DO change the launch angle by the dwell time of the rifle in recoil
Therefore, faster load, hits lower .. heavier bullet, same speed, hit higher, ... toss up if you are changing to heavier bullet and faster speed...

As I said, angle of gun remaining equal, etc. The dwell time you refer to and the change in movement of the gun will depend upon the shooter, the load, the gun, and many other variables and, therefore, cannot be predicted from shooter to shooter and situation to situation.

I disagree -- this isn't "does Bob shoot the rifle higher than Sam?" .. It must assume the same shot, with the least variables possible to simulate real world ..

I would imagine that even in a return to battery rail gun would see the same results .. faters bullets of the same weight hit LOWE...


"at some point downrange" sure, that COULD happen, that it would have a better bc and therefore CARRY farther ..

But let's hash that out ..

ASSUMING rezero for 150 yards with each load .. (we will uncomplicate the discussion ..
ASsume a 6" "bullseye" and let's play the MPBAR game .. maximum point blank range ... assuming the bullet can NOT travel 3" about or 3" below point of aim, what's the DIFFERENCE .. I'll put it in quicktarget, and make it the LARGEST delta in velocity and BC ... and you might be stunned for results ..

3030 winchester , 170gr FP, 2350fps, max PBR 184 yards, 30-378 190gr hornady spbt, 3400fps, 233 yards .. zeroed at 150 yards

FIFTY yards difference (well, 49) from the lowest to the highest velocity and horrible to excellent BC .. 50 yards ...

Let's go back to the 300 win ... that's a great one .. lets look at 165gr at 2900 and 3100fps ..

213 yards at 2900fps
219 at 3100fps ...

NOW, change that to 180gr matchkings .. at 3100 fps .. the "difference" assuming all the same as above?
220 yards .. 1 yard difference for super improved BC ..

Not in a big bore, but a nice little medium

And, for the record,
@100 yards - Height above LOS for 180gr at 3100fps, zeroed for 150 yards +.08
2900fps zeroed for 150 yards +.09 ..

Quickload to quicktarget calcs .. there is NO doubt about it, the faster load hits LOWER on a rifles zeroed for the slower load

But i've only had a chrono for 16 years, and did these experiments because it confounded my why a KNOWN faster load hit lower ..

If you zero the rifle with a 2900FPS load, and then shoot a 3100fps in the same gun, nothing but speed changing, it will hit LOWER.. every time.

I don't mean to be mean, so please don't take it personal .. its counter intuitive ..

quote:

Originally posted by jeffeosso:
btw, it is a MISNOMER that a bullet dropped at the muzzle will hit the ground at the same time ..

condition must be, with the bore perfectly aligned with the ground, and immobile, a bullet dropped from the bore height will hit the ground at the same time ..

This is my only point....everything else is variable....."just accept it." your words not mine.

quote:

And if you put boiling water into a freezer it will turn to ice faster than if you start with cold water?

And if you do the same with ice cream the younger the average age of the occupants of the house the faster it will disappear.

You would think that the bullets in the 30-06 and the .300 (the only ones I'm familar with) would drop but when you consider the barrel harmonics, all bets are off. I've had changes in powder and velocity cause the groups to wonder all over the target.
It would be a simple thing in load development if you were shooting two inches low with a safe load to add a couple of grs of powder and bring it up but that doesn't always (or seldom in my experience) happen.

Grenadier
You can prove it to yourself very quickly .. zero a rifle for a low book load at 100 ... and then fire a high book range set to make a group .. will it hit higher or lower, in the same gun, with the same shooter, same bullets? it'll cost you all of 10 bullets

Ted,
I was correcting a long mistated position.. a bullet dropped the bore height of a sited in rifle will hit SOONER because gravity is a constant .. whenever someone says "they hit the ground at the same time" then the conditions must be "in a rifle that does not angle up, and the bullet does not cross the POA of the bore ...

why? because if it does, the bullet has a rise and fall above and below the bore .. and that max height has to be taken into account ... if it's goes up 2 " then it has to go down 2" and if the begining height is 36", 4" is signifigant.. and the bullet dropped will therefore hit first.

I do have passion for keeping concepts correct, like ones that are not intuitive .. ESPECIALLY when they are "common sense" that just doesn't work.

Grenadier ..
If I raise my front sight 10% higher than the sighted in height, which way does the bullet impact the previous sighting? .. Down, of course ... why? you are effectivly aiming lower ... which is exactly what happens when a faster/same weight bullet leaves the barrel.

jeffeosso.... My points are very simple.

I am not useing the variable of a barrel pointed UP!

Also you seem to be talking to me when you say "common sense" or is this a jab at some others, or all....clarify please

Ted

Ted,
Not a jab at you ..

quote:

Originally posted by Hot Core:
.....
-----

Hey Ray, Feel free to vote what you think would happen based on your other cartridges. The wide spread of selections I see this morning could result in some good discussions.

Why do you think the 270Wins POI remains about the same with both changes in Velocity and Bullet weight?
.....

I have no idea why my 270 does this:



Just glad it does!

quote:

Originally posted by jeffeosso:
Ted,
Not a jab at you ..

I thank you then, kind sir.

Actually if a bullet is fired flat without any up to it at all and another is dropped at the same time, the bullet that is fired would not hit the ground at the same time as the bullet that is dropped.

The fired bullet dose have a slight lift component to it as it fly's thru the air, therefore the fired bullet would still be flying when the dropped bullet hits the ground

I helped with load development on a '06 this spring. As the loads got hotter, the POI changed to the right by some 3 inches (progressively as we reached max). No changes in elevation.

quote:

Originally posted by enfieldspares:

quote:

When the bullet weight or powder quantity increases or decreases the barrel vibrations change. Each rifle is different, so the only way to know what a rifle will do is shoot it off a bench rest.

The British SMLE in 303 (not the No4) had an unusual compensation characteristic in fact. The harmonics were such that it grouped better at long distance than did the No4.

As explained it was by fluke "just right" so low velocity rounds and high velocity rounds exited the barrel at just the right point to cause a smaller group.

According to E.G.B. Reynolds, who is one of the "Deans" of Lee-Enfield design bolt rifles, test results are "inconclusive" when it comes to comparing the compensation of No. 1 Lee-Enfields and the No.4 versions, depending on the Mark of cartridges used, and the weight of the factory barrels fitted. He & Robin Fulton both note that the causes of "positive compensation" are cartridge bullet weight & firing pressures, barrel weight, body (action) flexibity, and the method(s) of stocking up employed.

They both note that when the Canadians approved use of the 7.62 NATO cartridge (1964) in the No.4s manufactured at Long Branch, an early result was very poor accuracy at up to 600 yards, but very fine accuracy at 900 yards.

The reason for the better acuracy at the longer range was a pronounced degree of positive compensation... almost exactly like that found in the No.1 Mk 3 when the transition was made from Mark 6 ammunition to the use of Mk 7 as target ammunition in it, in 1919.

if you dropped a 36 gr. .22 rf bullet and a 1 lb lead ball at the same time they will hit the ground at the same time................. gravity is constant...................................

For those of you who believe the Increase in Velocity will cause it to either go Up or go Down, have you given any thought as to the Harmonic Node changing???

Here...I will piss everybody off...the question as phrased is stupid.

Because it is asking a question but not qualifying all the other variables...such as is the gun being shot off hand is the gun in a vice...

So unless you are going to qualify all the parameters lets not ask vague questions and then intellectually masturbate about all the variables we decided to included or not include...

When two identical projectiles are launched at differnt velocites parallel to the ground with all other factors held constant the faster traveliing projectile will be higher at the same distance.

You will notice...I mentioned nothing of barrels.

Yes, I am in a grumpy mood

Ted,
More than welcome -- The "common sense" remark, looking back, certainly could have been taken that way.. not what i meant.. think the people that still say centrifigal force, and mean an arced force ...

quote:

Originally posted by RaySendero:
I have no idea why my 270 does this:

Just glad it does!

Ray, Nice groups. I wonder what the velocities are on those 2 groups .. if they are close, which the weight and charges being so close i expect that they are, then you have demonstrated that the heavier bullet, at the same weight, hits higher.

quote:

Originally posted by tasco 74:
if you dropped a 36 gr. .22 rf bullet and a 1 lb lead ball at the same time they will hit the ground at the same time................. gravity is constant...................................

Tasco,
You are close to correct, and if you said, "if you drop a lead ball from the name NET height as a 22, they hit the ground at the same time due to the constant accelleration OF the force of gracity. Why? or better, why make the distinction? Because while the intent of your statement IS true, proving it would be false. The lead ball, placed at the height of the barrel has LESS distance to travel than a fired and ASSUMED to be sighted in, rifle


Its VERY unlikely that you have a 22 that leaves the barrel and ONLY travels down.. if your 22 is sighted for 100 yards, the barrel is angled UP for the the sighting system to be usefull. Your bullet cross the plane of the RELEASING angle of the bore and the plane of the line of sight TWICE before it reaches 100 yards .. once at about 25 yards (give or take) and once at impact. This can be several inches, and since teh force of gravity IS a constant...
example
basic height 36" inches along bore BOTTOM line
Bowling ball set at 36"
when fired, the barrel is angled UP in relation to gravity.. the bullet travels UP about 2.5 inches (in a 22 sighted in at 100 yards), crossing the line of sight at about 25 yards, and then falling back toimpact, -2.5 inches..and since fired at an angle, and over 100 fps, air resistence does come into account, but we'll ignore it. The angle of attack is PROBABLY small enough to ignore, and is NOT netted out, as that distance is traveled twice. We'll ignore it. BUT we can't ignore the TIME and force of graivty.

that 5 inches (remember, its more but not much more, takes TIME to traveldistance, even under contant acceleration

it take the bowling ball .43 seconds to travel 36 inches
It takes the bullet .46 seconds to travel 41 inces

IF the bowling ball was set at ~41 inches, which is ABOVE the line of the bore, with some very simple reasoning, then they would hit the ground at the same time.

and I swear, in this thread, this is my last post on trying to debunk persons saying a ball and a bullet hit at the same time. If placed at the same level, and the rifle is USEFUL as a rifle, (therefore sighted in at some distance like 25 or 100 or even 1000 yards) then the ball will hit the ground FIRST, as it will have less distance to travel AND the accelleration of the force of grvity is a constant

I wish cooperscool would post a little something to this thread and everyone could talk about a different type of trajectory.

This is like watching four blind guys describe the elephant. However,can someone splain this to me? 9.3x74, 250 woodliegh r. n. Viht. n140 53 gr. 2099 fps,54-2131,55-2148,56-2263,57-2275,58-2314, all shot from a cold barrel. starting at 2099fps, aiming at the same spot on the paper, each bullet hit higher than the one before it. 270 win. sierra 150 grn. RL22, 51 gr. 2573 fps,52-2656,53-2678,54-2834, 55-2893. Same as above,except each bullet hits the paper a bit lower than the one before it. Could it just be the difference in velocity combined with muzzle rise due to recoil? I think that is what this poll is about. Yes, I am aware that a bullet does not rise when it leaves the barrel.

eny,,,
to clarify .. bullets don't LIFT but they DO travel above the line of sight .. twice ... that's because they are launched at an up angle, relative to gravity, and the bullets ARC

Yes jeffeosso, I completley agree, and understand the ballistic arc.

quote:

Originally posted by Mike_Dettorre:
...the question as phrased is stupid.

Because it is asking a question but not qualifying all the other variables...such as is the gun being shot off hand is the gun in a vice...

So unless you are going to qualify all the parameters lets not ask vague questions and then intellectually masturbate about all the variables we decided to included or not include... ...

Hey Mike, Feel free to add any "qualifying ...variables" you desire.

Does the (#9) ding in the gun's finish matter?

quote:

Originally posted by jeffeosso:

quote:

Originally posted by RaySendero:
I have no idea why my 270 does this:

Just glad it does!

Ray, Nice groups. I wonder what the velocities are on those 2 groups .. if they are close, which the weight and charges being so close i expect that they are, then you have demonstrated that the heavier bullet, at the same weight, hits higher.

Jeff, No I don't think so.

That 1/4" elevation difference for the heavier load didn't hold for all cases.

I lost a bunch of pics and my reloading notes in 2003 due to a computer virus - That pic just happened to be left on my camera - Its all I have left of the load work I did for my 270 back then.

I had pics of more groups - A couple with 2 130s CLs, 2 135 SMKs, 2 140s ILs and 2 150 SGKs all touching but not consistently running up with bullet weight.

I completely understand trajectory and agree that a bullet flies in an arch to hit a 100 yard target. I also agree that a bullet dose in fact pass thru the line of sight, rises above it and then drops into the target. At least at most ranges that we shoot at.

But the fact remains that bullets do develop a slight lift component during flight and they do lift slightly –very slightly but none the less they do have some lift to their flight. -- They do not fly with their point directly on axis to the line of flight but do fly with their nose pointed slightly up to the line of flight and do develop a slight lift component. Therefore a bullet in flight will not hit the ground at the same time as a dropped bullet or bowling ball or any other solid object.

I completely do agree that a dropped bowling ball and a dropped bullet would result in both hitting the ground at the same time provided the bullet wasn’t shot from a rifle and flying thru the air, even if the bowling ball has the arch of the bullets flight factored into it's fall, it would hit the ground and the shot bullet would still be flying after the bowling ball hits the ground due to it's slight lift component.

Gene