Why does

[Freightman]

a heaver boolit hit higher? I was loading some 45 acp 200g SWC and didn't have enough boolits cast, I like to fill all the cases I have primed so I adjusted the load to what the books say and loaded some 255gr that I use for my 45 Colt. Went to the range and the 200gr hit POA at 20yds, but the 255's hit three inches high at the same POA, please explain the differencs the loads were for the 200gr 10.2gr AA#7 per Accurate Arms and LEE manuels the 255's was 9.1 gr AA#7 per the same manuels.
No big deal just curious.

[Shiloh]

Heavier, and slower recoil from the heavier boolits allow more time for the muzzle to rise.
Thats how it was explained to me. Makes sense

Shiloh

[S.R.Custom]

Heavier bullets are longer, and as a result, have more surface area. That, combined with the spinning action imparted to the bullet by the rifling, causes the bullet to climb into the air, much the same way a spinning golf ball climbs into the air when struck correctly by a golf club. And since a heavier bullet has more surface area, it climbs more...

I'm kidding. See post above.

[Glen]

SuperMag, you had me going there. Good one!

[Dennis Eugene]

LOL Supermag had me going also.
To put it simply the heavier bullet takes longer to leave the barrel, allowing the recoil to cause the barrel to rise higher before the bullet has a chance to exit. Dennis

[2ndAmendmentNut]

So, in theory if you clamped your gun in a vise so that there would be no muzzle climb, would all the boolits hit the same place?

[mooman76]

A lighter charge will sometimes hit higher for basically the same reason.

[Edubya]

So, in theory if you clamped your gun in a vise so that there would be no muzzle climb, would all the boolits hit the same place?
Some people have done that at 25yds. I've had the lucky occasion to put five .44mag boolits into an expanded hole. That hole grew to 3/4", but I've only done it once.
I think there are too many variables for alloys, primers, brass, crimp, fouling plus the wind and other intricate details that I can't even imagine for boolits to go in the exact same hole, even clamped down in a one-ton vise.
EW

[S.R.Custom]

So, in theory if you clamped your gun in a vise so that there would be no muzzle climb, would all the boolits hit the same place?

In theory, no. If both heavy and light bullets left the muzzle at the same velocity, the superior BC of the heavier bullet would allow it to retain more of its velocity over distance. As a result, the heavier bullet would hit higher.

In practice, however, that difference in height out to 50 yards or so would be so small as to be negligable, and they would appear to hit the same place. Out past 50 yards, tho, and you'd see the lighter bullet start to drop much quicker.

[BOOM BOOM]

HI,
In the real world, it would be difficult to even get the 2 bullet wts./&designs to even match barrel exit velocities. As even they are averages, & would have different standard deviations. Then of course different B.C. & different trajectories. It goes on & on.
Short answer is heavy bullets have more dwell time in barrel as the muzzle lifts under recoil, & so exit barrel at a higher point in in the recoil arch.

[yondering]

As a general rule of thumb:
-Slow bullets hit higher
-Heavy bullets hit higher

You can apply this to make your target and hunting loads have the same POI (or pretty close). Slow light bullets for target use, fast heavy bullets for hunting.

[44man]

Only two things to remember, handguns are recoil dependent for POI and also dependent on barrel time.
Even a tiny change in grip pressure or arm stiffness is bad as is letting a gun "roll."
Welcome to the crazy, wacky world of the revolver! [smilie=b:

[Ricochet]

In theory, it's simply the ratio of the masses of the bullet and the gun. For every action, there's an equal and opposite reaction. Apply a given amount of momentum to the bullet, and the gun gets the same amount of momentum. The bullet moves a certain distance down the bore, the gun moves backward in the same time that distance times the ratio of the masses of the bullet and the gun. That wouldn't affect the point of impact, except that the gun is supported against the recoil thrust below the bore line, so as it moves rearward it also pivots upward while the bullet is still in the barrel. With a heavier bullet, the gun moves to the rear and pivots upward more while the bullet is still in the barrel than it does with a lighter bullet that has less momentum. In practice other factors enter in with the mass of the supporting hand(s), the firmness of the grip support, etc., and surely even pistols have barrel harmonic vibrations.

Rifles do the same thing, and it's very noticeable with heavy recoiling rifles if you change the firmness of the butt's support against the shoulder. Sight one in on the bench, and the POI will be a little different if you shoot it offhand, sitting, kneeling, prone or some other field position. Let someone else sight in your rifle, and it won't likely be sighted in just right for you.