heavy vs light loads POI

[upstate88]

Ok i am pretty savvy with trajectory, twist, and bullet weight. But why if I zero a light bullet at 100 do the heavy loads hit higher than the light ones? Can someone point me to an article or explain it to me? I zeroed a 55 grain at 100 and the 62 was 1.5" high, and the 77 grain was 3" high, all factory loads.

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[DizzyJ]

Don't know of a hard and fast rule for determining that.

 

[JuglansRegia]

Well, it happens in handguns too, what I heard is the slower projectiles spend more time in the barrel so they kind of get caught in the recoil push which ends up pointing them higher by the time they leave the barrel.

 

[No_Regerts]

Regardless of the reason behind it, its the reason I NEVER switch loads without re-zeroing.

 

[KKG]

Well, it happens in handguns too, what I heard is the slower projectiles spend more time in the barrel so they kind of get caught in the recoil push which ends up pointing them higher by the time they leave the barrel.

That's correct!

 

[upstate88]

Very good point, something some over look when getting a new box of ammo for hunting season. 3" high at 100 could translate to a miss pretty easy.

 

[DizzyJ]

Well, it happens in handguns too, what I heard is the slower projectiles spend more time in the barrel so they kind of get caught in the recoil push which ends up pointing them higher by the time they leave the barrel.

That was going to be my reply for a handgun load. Rifle, not sure if it works exactly the same.

 

[upstate88]

I am wondering if it has more to do with the powder charge. Could it be that, in a round with a heavy bullet, they put more juice behind it to get the velocity it needs?

 

[Greenbug]

I am wondering if it has more to do with the powder charge. Could it be that, in a round with a heavy bullet, they put more juice behind it to get the velocity it needs?

Usually the opposite is true.
Lighter bullet = Heavy powder charge
Heavier bullet = Lighter powder charge

Powder burn rates come into play and etc... but generally the above holds true.

 

[Pandaz3]

It certainly is consistent regardless of load as the group is in different location, for me I get tighter groups with the 55's too. So why do I buy this more expensive heavier 'match' ammo, I guess for longer range.

 

[OldBroad44]

Considering handguns and ordinary handgun distances, the harder a load recoils, the higher the point of impact. Heavier bullets at equal velocities recoil harder, so print higher. With equal bullet weights, the one with higher velocity recoils more, so prints higher. Usually manufacturers change both bullet weight and velocity simultaneously, so things can be unpredictable. However, usually heavier bullets are also given more powder and are thus heavier recoiling, so they print higher. Basically, the heavier the recoil the more the load prints high. At handgun distances the effect of heavier recoil lifting the bullet as it emerges from the barrel matters much more than the effect of bullet weight or speed on trajectory.

At rifle ranges there is the added factor of flatness of trajectory. So with equal bullet weights, the bullet with higher velocity recoils more, which raises the point of impact. But the faster bullet also has a flatter trajectory, which lowers the point of impact at some points in bullet's path and raises it in others.

The firmness of your grip on the gun changes the recoil, so can change the point of impact. So if you fire a heavy revolver with heavy loads from a rest with a relaxed grip on the gun, the recoil will be greater than when you hold the gun firing offhand, translating into a higher point of impact.

 

[Member 5605]

heaver loads, the bullet leaves the barrel later than a lighter bullet (slower, longer barrel dwell time and more.. muzzle flip).

Lighter bullets while snappier, leave sooner on the muzzle flip.

Ergo, lighter bullets impact lower.

This would be the case if you had it in a vice and not in your hands.

 

[ron]

Considering handguns and ordinary handgun distances, the harder a load recoils, the higher the point of impact. Heavier bullets at equal velocities recoil harder, so print higher. With equal bullet weights, the one with higher velocity recoils more, so prints higher. Usually manufacturers change both bullet weight and velocity simultaneously, so things can be unpredictable. However, usually heavier bullets are also given more powder and are thus heavier recoiling, so they print higher. Basically, the heavier the recoil the more the load prints high. At handgun distances the effect of heavier recoil lifting the bullet as it emerges from the barrel matters much more than the effect of bullet weight or speed on trajectory.

At rifle ranges there is the added factor of flatness of trajectory. So with equal bullet weights, the bullet with higher velocity recoils more, which raises the point of impact. But the faster bullet also has a flatter trajectory, which lowers the point of impact at some points in bullet's path and raises it in others.

The firmness of your grip on the gun changes the recoil, so can change the point of impact. So if you fire a heavy revolver with heavy loads from a rest with a relaxed grip on the gun, the recoil will be greater than when you hold the gun firing offhand, translating into a higher point of impact.

As considering handguns slower moving bullet leaves the barrel later hitting the target higher. Example is 357 and 44 'Magnum' loads vs.low velocity 'Target' loads. The target loads strike the target higher. FYI The heavier the bullet the less the
powder charge. I started shooting and reloading the 357/38 in 1980.