Handgun trajectory compared to rifle trajectory

[Korporal]

Hey.
I've been told that if you compare to bullets in any given handun caliber, lets say .45LC, a 200grs bullet will have a lower POI than a 250grs bullet?
Why??? I cannot understand why? In my rifle, the heavier bullets fall faster to the ground than the lighter ones? At least I am pretty sure, I think, I'm most certain to remember...!:sad:
Weird how the doubt comes creeping when you think enough about things you are very sure of.
Can some one explain this for me please.
Please feed it to me with a teaspoon!

Korporal

[William Yanda]

Korporal
It's physics. As I understand it, whatever the load, the larger bullet has more inertia to overcome. Since the opposite and equal result tends to raise the muzzle, a heavier bullet will exit the barrel later, at a higher angle, than the lighter bullet. Thus, a higher POI. If you could take the muzzle rise out of the equation, the gravity dragging the heavier bullet down sooner, as experienced with a rifle, would be the dominant factor. If I am wrong, I'm sure someone here will correct me.
Regards

[BruceB]

It's a combination of two things.

1.Barrel time: The heavier bullet, traveling slower than the lighter one, spends MORE TIME in the barrel before it exits the muzzle.

2. Recoil: Handguns, being less-supported by the shooter's body than is a rifle, start to move in recoil BEFORE the bullet leaves the barrel. The upward motion of the muzzle in recoil affects the point-of-impact of the bullet.

Therefore, taking these factors together, the muzzle rises HIGHER before the slower bullet departs, than it does when the lighter and faster bullet is fired and leaves the gun in a shorter time period.

Hence: lighter bullets hit Lower than do the heavier ones.

Naturally, as the range lengthens, the trajectories can change their relationship, but at "normal" handgun distances the heavy bullet generally hits higher than the lighter one.

[Sensai]

Well, kinda/sorta. In a handgun the barrel dwell time of a heavier projectile does cause the projectile to leave the barrel later, therefore at a higher angle, causing a higher point of impact on the target. With a more stationary barrel, like a rifle in a rest, this is not true. That said, the projectiles "fall" at the same rate. They just get to the target at different times of flight. If you fire a 200 grain bullet and a 250 grain bullet at the same velocity, from a stationary barrel, they will have the same point of impact on the target (discounting drag caused by nose design). The difference comes to bear when you consider the chamber pressure required to attain the velocity. A lighter projectile requires less pressure to attain a given velocity than a heavier projectile in the same length barrel. If you load to the same, or nearly the same, pressure level; the lighter projectile will have a higher velocity than the heavier projectile. I hope that I haven't confused the subject even more. Best wishes

[Artful]

Exactly as BruceB explained it

http://www.gunnuts.net/2013/12/09/revolver-science-why-heavy-slow-bullets-hit-higher-than-light-fast-bullets/


To understand what causes the revolver to act the way it does, you have to remember that in a revolver, none of the recoil energy of a cartridge going off is being used to operate the gun. Thus, when the cartridge goes bang, the effect of recoil is immediately applied to the shooter, causing the gun to begin to pivot in recoil while the round is still in the barrel. While this only last for fractions of a second, those fractions of a second are enough time to change where the round will impact. Let’s look at two bullets of different weight and different muzzle velocities as an example.

A 158 grain bullet fired at 750 FPS is traveling at 9000 inches per second. At that speed, it will take approximately 0.000333 (repeating) for the bullet to travel three inches of barrel. This disregards chamber gap, forcing cone, etc. A 125 grain bullet at 900 FPS (10800 inches per second) will travel the same distance in 0.0002778 seconds. Finally, a 110 grain bullet at 1100 FPS (13,200 inches per second) will travel 3 inches in 0.00022728 seconds. Again, we’re dealing with tiny fractions of seconds here, but they do make a difference.

The physics become more complicated when you’re trying to figure out how much exactly the difference in velocity will affect the point of impact, but a good rule of thumb is the lighter the gun, the bigger the difference. Also, having weight forward of the revolver’s pivot point will also help mitigate this issue. For example, when I’m shooting a 2 inch j-frame, the difference between a 110 grain JHP at 1100 FPS at a 158 grain LRN at 730 FPS is profound, out of a six inch Security Six it’s not as bad.

On some fix site'd handguns I have adjusted the load to match the sights when accuracy was of highest importance to the owner. You can also do that for rifle loads - match a full power hunting load and a plinking load (usually at a shorter range) so that you don't have to change the sites to use in different seasons (deer / squirrel).

[osteodoc08]

In actual ballistics, it is not factual. It is a phenomenon.

I was shooting at some sticks in a creek the other day with my Mountain Gun. It sailed right over the top by about a foot......for the reasons outlined above.

[Silver Jack Hammer]

The trick question is; If you drop a big rock and small rock at the same time which one hits the ground first? The answer is, both hit the ground at the same time. Gravity is a constant and it acts on all objects the same. If you throw one rock straight horizontally forward and drop the other rock at the exact same time, they will both hit the ground at the exact same time, regardless of how much they weigh. That's why ballistic trajectory tables only factor sectional density and velocity, not boolit weight. If you drop a rock and a feather at the same time in a vacuum they will both hit the ground at the same time.

So when you consider point of impact distance, it's calculated by where the boolit dropped to at it's time of flight. The more ballistically efficient the boolit is, the farther downrange it's going to have traveled during it's drop as measured in fractions of a second.

You are asking about different boolit weights and point of impact measured out of the same handgun held in the hand, yes the handgun under recoil is going to arc up in recoil more with the heavier boolit and the heavier boolit is generally going to be in barrel for a longer period of time than the lighter boolit moving faster. I shoot fixed sighted Colt SAA's a lot with different boolits and as a rule, slow-moving boolits hit higher than faster moving boolits do and heavier boolits impact higher than lighter boolits.

[SSGOldfart]

IT just happens ????????????? adjust for it ?????
I shouldn't try to think before noon and a couple more pots of coffee:arrow:

[osteodoc08]

The trick question is; If you drop a big rock and small rock at the same time which one hits the ground first? The answer is, both hit the ground at the same time. Gravity is a constant and it acts on all objects the same. If you throw one rock straight horizontally forward and drop the other rock at the exact same time, they will both hit the ground at the exact same time, regardless of how much they weigh. That's why ballistic trajectory tables only factor sectional density and velocity, not boolit weight. If you drop a rock and a feather at the same time in a vacuum they will both hit the ground at the same time.

So when you consider point of impact distance, it's calculated by where the boolit dropped to at it's time of flight. The more ballistically efficient the boolit is, the farther downrange it's going to have traveled during it's drop as measured in fractions of a second.

You are asking about different boolit weights and point of impact measured out of the same handgun held in the hand, yes the handgun under recoil is going to arc up in recoil more with the heavier boolit and the heavier boolit is generally going to be in barrel for a longer period of time than the lighter boolit moving faster. I shoot fixed sighted Colt SAA's a lot with different boolits and as a rule, slow-moving boolits hit higher than faster moving boolits do and heavier boolits impact higher than lighter boolits.

While all of this is true, we are now negating velocity and time constants. The faster boolit (assuming same BC) will go much further before hitting the ground, albeight at the same time.

Ballistic physics are very interesting to me. Its neat to see a slower muzzle velocity caliber surpass that of a much faster caliber at 500, 1000, 1500+ yards because of superior Ballistic Coefficient.

[histed]

OK, got it so far. I was going to ask this if the OP didn't. Adjust the load? I'm shooting Lee 356-125-2R over 4.4gr of Unique, not at max. To raise the POI (my sights are fixed) should I up the charge, switch to a faster powder, like Bullseye, or switch to a 147 gr boolit? I'm hitting about 5" low at 10 yards.

[Artful]

change to the heavier boolit to have it hit higher.
OR you can often times change your grip to change the impact - not as noticable as changin ammo thou.

[KYCaster]

OK, got it so far. I was going to ask this if the OP didn't. Adjust the load? I'm shooting Lee 356-125-2R over 4.4gr of Unique, not at max. To raise the POI (my sights are fixed) should I up the charge, switch to a faster powder, like Bullseye, or switch to a 147 gr boolit? I'm hitting about 5" low at 10 yards.


Pick the load you want to use then file the front sight down to raise the POI.

Jerry

[histed]

Thanks, its what I thought. I either go to a 147 grain or try to find an adjustable rear sight. I have a SCCY (which I really like) so filing the front sight isn't really a good option.