Sight regulation and bullet weight

[kb9424]

I’m having a smith regulate sights on a 44mag vaquero and have a question on bullet weight. If I have it regulated for a 280gr bullet is there a possibility of effectively using bullets ranging from 260gr to 300gr or am I pretty much married to that 280gr load?

[kb9424]

And it appears I posted this question in the wrong section….

[bigbrowndog]

It all depends on how interested you are in playing with speed, weight, and powder choice, they all can effect how a bullet comes flying out the barrel. I believe David ?Bradshaw posted the effects and contributors to sight regulation here in this forum somewhere. I think I saved it but I’ll have to look.

Trapr

[bradshaw]

Sept 29, 2023 8:46:50 GMT -5 bigbrowndog said:

It all depends on how interested you are in playing with speed, weight, and powder choice, they all can effect how a bullet comes flying out the barrel. I believe David ?Bradshaw posted the effects and contributors to sight regulation here in this forum somewhere. I think I saved it but I’ll have to look.

Trapr

*****

The formula for sight correction may be expressed a couple of ways. A useful feature is to see it as a triangle.

Sight triangle, all measurements in inches----(thousandth-inch)
* SIGHT RADIUS.
* ERROR----distance between POA (Point of Impact) and POI (Point of Impact).
* DISTANCE to TARGET.

Steps
1) Multiply sight radius times error.
2) Divide #1 by distance to target.
3) Product of step #2 = CORRECTION.

Example
* Sight radius = 6.25”
* Error = 4.0”.
* Distance to target = 25 yards (900”).

6.25” x 4.0” = 25.0".
25" divided by 900” = 0.027”
Thus, an elevation or windage adjustment of .027” moves POI 4” @ 25 yards.

Bullet weight and velocity, handguns
Recoil is set in motion as the bullet accelerates in the gun. Since the hand is below bore axis, the muzzle inclines upward. The vast majority of recoil happens after the bullet is long gone. The heavier the bullet, the longer it takes to accelerate, and the more time it has to lift the muzzle before exit. A heavy bullet raises the muzzle higher than a light bullet, causing the heavy bullet to register a higher POI.

BARREL TIME
The same bullet: a load with longer barrel time strikes higher on the target.
David Bradshaw

[kb9424]

Thank you both. Is there any way besides trial and error to roughly estimate POI based on wt and velocity? Hypothetically speaking, a 260gr @ 1400 fps, 280gr @ 1300 fps and 300gr @ 1200 fps all impacting at a similar POI?

[bigbrowndog]

Sept 29, 2023 10:12:03 GMT -5 bradshaw said:

Sept 29, 2023 8:46:50 GMT -5 bigbrowndog said:

It all depends on how interested you are in playing with speed, weight, and powder choice, they all can effect how a bullet comes flying out the barrel. I believe David ?Bradshaw posted the effects and contributors to sight regulation here in this forum somewhere. I think I saved it but I’ll have to look.

Trapr

*****

The formula for sight correction may be expressed a couple of ways. A useful feature is to see it as a triangle.

Sight triangle, all measurements in inches----(thousandth-inch)
* SIGHT RADIUS.
* ERROR----distance between POA (Point of Impact) and POI (Point of Impact).
* DISTANCE to TARGET.

Steps
1) Multiply sight radius times error.
2) Divide #1 by distance to target.
3) Product of step #2 = CORRECTION.

Example
* Sight radius = 6.25”
* Error = 4.0”.
* Distance to target = 25 yards (900”).

6.25” x 4.0” = 25.0".
25" divided by 900” = 0.027”
Thus, an elevation or windage adjustment of .027” moves POI 4” @ 25 yards.

Bullet weight and velocity, handguns
Recoil is set in motion as the bullet accelerates in the gun. Since the hand is below bore axis, the muzzle inclines upward. The vast majority of recoil after the bullet is long gone. Nevertheless, the heavier the bullet----the longer it takes to accelerate----the more time it has to elevate the muzzle before it exits. A heavy bullet raises the muzzle higher than a light bullet, causing the heavy bullet to register a higher POI.

BARREL TIME
Given the same bullet, a load producing a long barrel time raises Point of Impact.
David Bradshaw

David somewhere you posted lighter bullet/heavier bullet, and faster powder/slower powder,faster bullet/slower bullet info and I looked in my notes and must have deleted it accidentally, I’d greatly appreciate reposting that info so I could re save it. It should help this fellow as well.

Trapr

[bradshaw]

Sept 29, 2023 11:01:50 GMT -5 kb9424 said:

Thank you both. Is there any way besides trial and error to roughly estimate POI based on wt and velocity? Hypothetically speaking, a 260gr @ 1400 fps, 280gr @ 1300 fps and 300gr @ 1200 fps all impacting at a similar POI?

*****

Short answer: NO.

Long answer: Yes, for a specific revolver of specified barrel length, for a specific cartridge bullet weight.

Note: grip pressure may reduce recoil, mostly after the bullet departs the muzzle. Unlike a constrictor snake, our musculature isn’t designed to maintain a death grip of serious duration. The sooner a new shooter learns this, the sooner he or she can relax and learn the direct relationship of BREATHING to SQUEEZE & FOLLOW THROUGH.

It is impossible to fight the revolver and hold a consistent POI (Point of Impact). To fight the gun induces flinch, ruins squeeze, and utterly destroys follow through. Anything that jolts squeeze throws the shot.
David Bradshaw

[blackmamba]

A lighter bullet would need to be slower than a heavier bullet to regulate the same. Lighter recoils less, so needs more time in the barrel to exit at the same point.

[kb9424]

Sept 29, 2023 14:11:33 GMT -5 bigbrowndog said:

Sept 29, 2023 10:12:03 GMT -5 bradshaw said:

*****

The formula for sight correction may be expressed a couple of ways. A useful feature is to see it as a triangle.

Sight triangle, all measurements in inches----(thousandth-inch)
* SIGHT RADIUS.
* ERROR----distance between POA (Point of Impact) and POI (Point of Impact).
* DISTANCE to TARGET.

Steps
1) Multiply sight radius times error.
2) Divide #1 by distance to target.
3) Product of step #2 = CORRECTION.

Example
* Sight radius = 6.25”
* Error = 4.0”.
* Distance to target = 25 yards (900”).

6.25” x 4.0” = 25.0".
25" divided by 900” = 0.027”
Thus, an elevation or windage adjustment of .027” moves POI 4” @ 25 yards.

Bullet weight and velocity, handguns
Recoil is set in motion as the bullet accelerates in the gun. Since the hand is below bore axis, the muzzle inclines upward. The vast majority of recoil after the bullet is long gone. Nevertheless, the heavier the bullet----the longer it takes to accelerate----the more time it has to elevate the muzzle before it exits. A heavy bullet raises the muzzle higher than a light bullet, causing the heavy bullet to register a higher POI.

BARREL TIME
Given the same bullet, a load producing a long barrel time raises Point of Impact.
David Bradshaw

David somewhere you posted lighter bullet/heavier bullet, and faster powder/slower powder,faster bullet/slower bullet info and I looked in my notes and must have deleted it accidentally, I’d greatly appreciate reposting that info so I could re save it. It should help this fellow as well.

Trapr

Trapr,

Is this the information you were referencing from Mr. Bradshaw? I had to go all the way back to Sept 2014 to locate it! I’ve done lots of reading in the past 24hrs…

“Notes----45 Colt

Barrel Time and Point of Impact (POI)
a) Long barrel time raises POI.
b) Short barrel time lowers POI.

Bullet weight & Point of Impact
a) Heavy bullet raises POI.
b) Light bullet lowers POI.

Same bullet----Powder Burn Rate (BR) affects POI.
a) Fast powder (fast BR) shortens barrel time to lower POI.
b) Slow powder (slow BR) lengthens barrel time to raise POI.
c) Medium powder (medium BR) puts POI between fast and slow powders.”

David Bradshaw

[bigbrowndog]

Yep, that’s it

Trapr