Factors Relative To Rifle Accuracy

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SeekHer
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Factors Relative To Rifle Accuracy

Post by SeekHer »

Factors Relative To Rifle Accuracy

HEAT = Increased pressure = increased velocity = higher impact
COLD = Decreased pressure = decreased velocity = lower impact

FASTER TWIST = Heavier bullets Stabilized
SLOWER TWIST = Lighter bullets Stabilized = Heavy Bullet “Waddles” side to side in flight

ELEVATION = Thinner air = less air resistance = higher impact
HUMIDITY = Increased humidity/air density = lower velocity = lower impact

ANGLE UP = (You will) Shoots lower
ANGLE DOWN = (You will) Shoots higher

You will have a tendency to miss because you will aim wrong
You will misjudge your distance when you are above or below your target (NO LASERS)
When looking up targets appear to be closer...When looking down they appear to be farther

The faster the barrel’s twist = The heavier the bullet stabilized

It’s because the method with which we usually calculate bullet energy is heavily tilted in favor of velocity. Double a bullet’s weight and you only double its energy if velocity remains the same. But double its velocity and energy increases fourfold!

Extreme velocity eventually destroys accuracy, as it will eat barrels…

The longer the barrel the greater the velocity, shorter the barrel the more accurate it is because it is stiffer and subject less to harmonic frequencies...

Caliber Twist
1” in xx"= one complete revolution of the fired bullet in that amount of barrel length

.172 9” For bullets heavier than 30 gr.
10” For bullets up to 30 gr.

.204/20 12” For all bullets.

.222 RF 14"* Twist for pistol barrels {RF=Rimfire}
16” Standard twist for rifle barrels
17"* Special twist for rifle barrels

.224 CF 8” For bullets heavier than 70 gr. {CF=Centerfire}
9” For bullets up to 70 gr.
12” For bullets up to 63 gr.
14” For bullets up to 55 gr.
15"* For bullets up to 55 gr. driven 4,100 fps or more
16"* For bullets up to 55 gr. driven 4,300 fps or more

6mm/.243 8” Special for VLD bullets over 100 gr.
10” For bullets up to 120 gr. and VLD under 100 gr.
12” For bullets up to 85 gr.
13"* For bullets up to 75 gr.
14"* For bullets up to 70 gr.
15"* Special for bullets up to 70 gr.

.257 9” For bullets heavier than 100 gr.
10” For bullets up to 100 gr.
12” For bullets up to 90 gr.
13"* For bullets up to 80 gr.
14"* For bullets up to 70 gr.

6.5mm/.264 8” For bullets heavier than 130 gr.
9” For bullets up to 130 gr.

.270 10” For all bullets

7mm/.284 9” For bullets heavier than 140 gr.
11” For bullets up to 140 gr.

.307 13"* Special size and twist

.308 8” For bullets heavier than 220gr.
10” For bullets up to 220 gr.
12” For bullets up to 170 gr.
14"* For bullets up to 168 gr.
15"* For bullets up to 150 gr.

7.65mm/.311 10” For all bullets

8mm/.323 10” For all bullets

.338 10” For all bullets

9mm/.355 14” For low-velocity wadcutters
16” For all other bullets

.38/.357 14” For low-velocity wadcutters
18” For all other bullets

.358 14” For all bullets

.375 12” For all bullets

10mm/.400 16” For all bullets

.411 14” For all bullets

.416 14” For all bullets

.44 20” For all bullets
16” For low velocity wadcutters

.451 16” For all bullets

.458 14” For all bullets

Twist chart from **Charlie Sisk Custom Rifles**

Twist/bulletweight/caliber chart from Lilja Barrels

Submitted by SeekHer

[[Category: Rifle]]
[[Category: Ammunition]]
[[Category: Shooting Tips and Techniques]]
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