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Faster loads shoot flatter than slower loads?

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9K views 45 replies 19 participants last post by  GunDr  
#1 ·
I was told that faster loads shoot flatter (lower), than slower loads. If this is correct, why would that be?

Thank you in advance, Rodbuster.
 
#2 ·
Rodbuster, that's not entirely fact. A fast load, one over 1300 FPS spreads faster than a slow 1100 FPS load does and gives one the impression it shoots lower. They both shoot to the same POI if measured to the pattern centers. Try it at 16 yards on paper and measure it for yourself?

Hap
 
#4 ·
What George said...

You can really see this with 357 magnum pistols and points of impact with full bore 357 magnum loads and light 38 target loads shot from the same pistol.

As recoil occurs the barrel will rise. The faster the round the sooner it exits the barrel and the less rise there will be - this will impact where the bullet strikes.
 
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#5 ·
The reason that a faster load drops less than a slower load is very simple. Time and Gravity. Gravity works independently of the forward velocity of the projectile. An object will fall in accordance with the acceleration due to gravity whether is has forward velocity or if it it is simply dropped vertically. However, shooting at a target at a fixed distance, a fast load gets to the target quicker than a slower load, therefore gravity has less time to act on the shot charge of the faster load, and therefore will shoot flatter than the slower velocity load. This can be an important consideration for long distance rifle shooting, however for shotgunning distances it is of no consequence. The difference will be fractions of an inch. So yes, from a theoretical and absolute viewpoint, faster loads will drop less. From a practial standpoint, the difference between a "fast" and a "slow" velocity load will be negligible.

Edit

OK...I crunched the numbers...Comparing drop distance of the shot charge of a load of 7.5's that started out at 1330 fps vs a load of 7.5's that started out at 1135 fps. At 40 yds, the faster load will drop 0.81 inches less than the slower load....
 
#6 ·
HSLDS, I have a question since I'm not into much handgunning at all.

If both loads you mentioned were shot with the handgun clamped securely (no upward movement) in a heavy vice, would that same thing still happen?

George, if that's true on an upward 'arc' move, how would it work when sandbagging the gun/shots from a stationary bench? How much difference can there be between a load exiting at 800 MPH versus another at 750? POI and pattern wise? I do agree that there's some differences in numbers but how much difference does it really make at 40 yards?

Hap
 
#8 ·
Hap,

Gravity not with standing, if the gun is held immobile then the point of impact should be the same for both rounds.

For John Saubak,

Yes, heavier bullets will tend to shoot higher - but for the same reason.

If you use the same weight bullet - one loaded to high velocity (357 mag 'full house'), and one to low velocity (38 target load) you should see the same type of difference in point of impact as well.

This assumes the pistol is allowed to move with recoil and it is easier to see in a 6" or 8" barrel as compared to a 2" barrel (different transit times).
 
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#14 ·
rodbuster, are you thoroughly confused now? Inkball, Pat, Tool and Hap state a perfectly valid scientific fact, but it is not germane.

Country Squire gave you the correct answer for a shoulder fired shotgun.

HSLDS give correct info for a handgun fired when hand held (sand bag rest or not). You can easily prove this to yourself. Using the same bullet weights, fire a .357 Magnum cartridge at a target. Now fire a .38 Special, then a .38 Long Colt. The .357 will be lowest, then the .38 Special and then the Long Colt. You will see a surprising difference in POI from just 20'.
 
#15 ·
You might be making the same mistake many hunters make when shooting at an angle to "parallel" to the ground.

Remember vectors from physics??

If you fire a rifle at 3000 fps, or a shotgun at 1250 fps horizontally then gravity imparts a downward acceleration of 32f/s/s.

If you fire at an angle to the horizon (up or down - it doesn't matter) a significant portion of that velocity is available to counter or overcome the effects of gravity (easiest to see as vectors - the angle can be defined by the sum of the two vectors - a large horizontal one, and a significant vertical one), the net effect is that you can essentially IGNORE the acceleration due to gravity.

The final result in this situation is that the bullet will strike higher than your aiming point because the velocity of the bullet counters the effect of gravity.

I know, it is counter intuitive, but it is true...
 
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#17 ·
HSLDS, when a bullet leaves the confines of the barrel wall, does it in fact rise or begin it's fall immediately? neither angle of the projectile nor speed can overcome or ignore gravity, can it?

Shooting up or down a steep incline on a long shot is very confusing to a lot of shooters. The distance they see in yards isn't in sync with the actual distance if both the target and rifle were on the same elevation plane, gravitational wise. Stand on a cliff and shoot your shot pattern into a still lake, it may be a hundred yards to the water from where you stand but only 25 yards out gravity wise. The pattern at 100 yards away will look and be the same size as it would at 25 yards on the level. 25 yards is the actual distance the target is away from the barrel for gravity's sake.

Hap
 
#18 ·
HSLDS,

The reason that a bullet will strike higher when you are shooting at a signficant upward or downward angle is because the only vector component that has anything to do with bullet drop is the horizonal component. If you are shooting a 400 yd shot, but it is at a 45 degree angle, the true balistic distance will only be 283 yds (cos 45 * 400 = 283). Velocity of a projectile has no affect on the actions of gravity upon that projectile.
 
#19 ·
Years back we had a customer who had bought a Remington replica single action revolver in 45 Colt (sometimes erroneously referred to as "long Colt"). With the 255 grain factory load it shot about 12" high. He wanted it to shoot to the sights at 25 yards and didn't want the sights altered. I tried 230, 225, 200, 185 grain bullets and they progressively shot lower but it wasn't until I tried a hollow based semiwadcutter of 155 grains that it shot to point of aim at 25 yards.

Recoil time in the barrel is the most common cause of the heavier bullets hitting higher. Heavier bullets take longer to exit than lighter ones and thus exit at a higher point of rise.

Of course, in response to the writer who asked what would happen if the gun were solidly anchored and could not move, I don't know. Haven't tried it, but I'd bet they'd shoot closer together than if it were free to move. Varying velocity with the same bullet will also alter point of aim.

There ain't no finite laws in this matter. Your results may vary.
 
#21 ·
ink ball,

You are correct on the 'velocity' issue - vectors measure force, not velocity (my mistake).

I think you and I are saying the same thing.

If you are shooting a 400 yard shot - it's still going to be 400 yards to the target. Where your logic is correct, I think you need to correct 'backwards' to a relative distance that has a cos 45 of degrees equal to the 400 yards.

Neil,

In an angled shot the disparity between the force of gravity and the force imparted on the projectile by the burning powder is so great you can essentially ignore the effect of gravity (this obviously depends on the size of the angle). It will be more significant for a rifle than it will be for slower rounds as in a shotgun.
 
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#22 ·
Capt Rick

"Fire a 30/06 180, or a 220 gr at 25 yards and then with the same rifle shoot the same bullets at a higher speed and I will guarantee you that the faster bullets WILL STRIKE LOWER PERIOD!!"

Now will the same thing hold true at 250 yards?

Bob Lawless
 
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#23 ·
At a distance where I could easily determine the pattern-center (mid-20 yards, as I remember) I shot five X-tra Lites and five Super Handicaps off a rest, alternating shots and measuring the distance of each pattern-center above the point-of-aim.

Not all the patterns-centers were in exactly the same place, but in this test there was no tendency for either the faster or the slower load to print consistently higher. That is, both shot in about the same place, to the accuracy that this sort of thing can be done without a machine rest.

Neil
 
#24 ·
What Savage99Stan says is true. All fixed sight revolvers have a front sight that is greater in distance from the center-line of the bore to the top of the front sight than the back sight. This difference takes into account the arc of the barrel during recoil. When you aim you are actually aiming below the point you want to hit. During recoil the barrel moves up and the bullet hits correctly if everything is correct.

If a fixed sight shoots high you need less velocity with the bullet you have or if that's not enough you will then need a lighter bullet. This allows less time for the barrel to arc up and makes the gun shoot lower.

If a fixed sight shoots low the tendency is to believe the trajectory of the bullet is at fault so a shooter thinks they need a faster/lighter bullet to make the gun shoot higher. Just the opposite is true. It's not the trajectory but the arc of the barrel that is making the gun shoot low. Changing to a heavier/slower bullet allows the barrel to arc more and thus shoot higher. This is dependant upon the weight of the projectile and how long in time it is in the barrel.

Check a fixed sight revolver - longer barrels show more than short barrels. Take a set of calipers and measure the distance from the center line of the bore to the top of the front sight. Then do the same with the rear sight.

I agree with Neil however concerning shotguns that any change would be slight.
 
#25 ·
"At a distance where I could easily determine the pattern-center (mid-20 yards, as I remember) I shot five X-tra Lites and five Super Handicaps off a rest, alternating shots and measuring the distance of each pattern-center above the point-of-aim.

Not all the patterns-centers were in exactly the same place, but in this test there was no tendency for either the faster or the slower load to print consistently higher. That is, both shot in about the same place, to the accuracy that this sort of thing can be done without a machine rest."

Neil

I lost a nickel bet, because of that test, to Neil several years back! My thoughts were that faster loads shot higher. I tested 1-1/8 loads at 1090, others at 1310 at 16 yards, about 12 shots of each. I even went to the trouble of marking a horseshoe shaped black aiming point to have an even amount of black showing all around on my white bead, with sandbags of course! As Neil says, measured to pattern centers, for shotgunning purposes, not much difference at all between the two speeds. The higher speed load does spread more and at first glance, it looks to shoot lower because of that spreading, not true when you put a tape measure on the centers from the top of the aiming horseshoe mark! Hap
 
#26 ·
The faster loads I believe shoot flatter, the distance to the target is the determining factor, The faster loads will make it appear to shoot higher as the shot gets to the target quicker than the slower loads like 1145 Vs 1250 fps
and the target does not travel as far before the shot breaks it.

The slower loads need a higher POI than the faster loads I am guessing on the distance or I should say POI needs to go 3-4 inches higher for the slower loads.

But you have to do this shooting targets set on straight aways and compare target breaks, but do this from the 27 yard line, post #3. You will see slight differences on target breaking quality.

Like an adjustment of just one to two lines on rib lowering or raising for the distance. I for one shoot a higher POI on Hdcp than 16yd.

When I first got my Seitz the 16 yd targets were totally smoke, ink balls all of them. It had a fixed rib they call it the 2 1/2 hihg shooter at that time, this was before the adj rib models. But I raised the comb one turn on the adj set screws for Hdcps to achieve the same results. I was shooting 3 dram 1200 Fps shells on Hdcp and 2/3/4 dram on 16yds.

I now mostly shoot 27 yard targets and have no need to adjust for 16s.

Take this for instance, shoot a Remington 870 or a 1100 or a Beretta 682
all with the sight picture you shoot and then pick up a Seitz or an Infinity
and you will be shooting over the targets because of the fast lock time.

The highest shooting gun from the factory with rib adjusted to it's highest setting is the Caesar Guerini, it will shoot 130% right out of the box, it shoots higher than the Kreighoff Special Trap, hands down.

I like a high shooting gun and the Caesar does it. It has a .740 Bore and long forcing cones, adjustable comb all the bells and whistles already done for you.

My full choke tube has a 19 inch pattern at 42 yards, very nice and even pellet distribution.

But now this is my intrepertation of fast shells Vs slow shells.


Gary Bryant
Dr.longshot
 
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