Point of Impact? Heavier bullets?


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CZSteve
November 22, 2004, 11:05 PM
Excuse my ignorance in advance, but...

I've read many times in various threads that a heavier grain bullet will usually impact with a higher POA than a lighter bullet.

Seems that the opposite would be true as the heavier bullet would have more gravitational drag.

Would someone please enlighten the ignorant. Umm, ie: me :uhoh:

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R.H. Lee
November 22, 2004, 11:08 PM
In my 642, a lightweight snubby, heavier bullets impact higher because the recoil is greater. a 125 gr bullet will hit at the point of aim at 10 yards.

Shmackey
November 22, 2004, 11:52 PM
Heavy bulllets fall at the same speed as light bullets. Galileo says so anyway. RileyMc has it right: gravity isn't even the point, as the angle at which the bullets exit is slightly different with different bullet weights.

P95Carry
November 23, 2004, 12:16 AM
I'd agree - the gun's movement during the milliseconds of bullet travel within the bore, will be the influencing factor on start of trajectory... and thus angle of exit.

I'd add tho - that we need to see the different weights exiting the gun at all but same ME ... so lighter/faster - heavier/slower - but same ME. The drop should not change significantly for a given cal... as the heavier for example, (if slower) carries greater momentum.

As ever - I stand to be corrected! :)

JohnKSa
November 23, 2004, 12:25 AM
In a given caliber, heavier bullets tend to both be slower and cause more recoil.

A slower bullet takes longer to exit the muzzle--that allows the muzzle to rise slightly higher before the bullet exits. That puts the bullet on the target a bit higher than one that exits faster.

When you add in the extra recoil, the effect is magnified.

If you look at some of the old target .38 revolvers, you'll see that they tend to have front sights that look impossibly tall. The higher front sight causes a lower point of impact to compensate for the slow, heavy target .38 loads' tendency to hit high on the target.

CZSteve
November 23, 2004, 07:30 AM
Now I feel foolish, completely forgot that weight is irrelevant w/ regards to the drop rate. :banghead:

However, thanks for answering the 'why' w/ regards to muzzle flip and a slower moving projectile.

Black Snowman
November 23, 2004, 11:16 AM
Don't feel bad CZsteve because heavier bullets normally travel slower so there is more filght time, and therefor more bullet drop, from gun to target. However, at the short distances that pistols shoot at this is overshadowed but the angle change.

You were probably just thinking of external balistics data that is repeated in many places. The info is everywhere and easily applied out of context.

Recoil is definately relevant. My new Ti Taurus 455 hits quite high with 230 gr PMC. I'm going to try some 185 gr reloads to see if I can get it to hit POA :)

B36
November 23, 2004, 07:00 PM
Today I was testing some 165gr lead bullets from two N frame revolvers, both 4". 1075fps

From Model 21-4, POI was 4" lower at 15 yards.
From 329, POI was 3" lower at 15 yards [lighter gun].

Both guns shoot close to POA at 15 yards with 200gr lead at 1000fps.

Combination of recoil and barrel time.

Jim K
November 23, 2004, 07:09 PM
For those who have not been tuned in, remember that recoil of a gun begins the instant the bullet starts to move, not like some pictures show with the bullet leaving the barrel before the gun moves.

So barrel time is an important factor, especially in a handgun, a point that police found out when they went from heavy bullets in the .357 to hot loads with 125 grain bullets. The hotter loads shot so low that some police had a problem qualifying, since the shooter had to aim at the neck of a silhouette target to get in the scoring area.

This puzzled a lot of people unfamiliar with the way a revolver recoils; one instructor explained to his troops that the load was designed so that aiming at center mass would shoot a bad guy in the b***s and incapacitate him faster. I guess that is one explanation!

Jim

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