Bolt Weight Formula 5w5h4z

Bolt Weight Formula Chinn claims that, ignoring friction: momentum of bolt = momentum of projectile + momentum of gas (+ momentum of barrel?) mbolt * vbolt = mbullet * vbullet + mgas * vgas (+ mbarrel * vbarrel?) Since pressure = force / area, the forces on the bolt face and bullet will differ by the ratios of their areas. force on bolt face / area of bolt face = force on bullet base / area of bullet base or force on bolt face = force on bullet base * (area of bolt face / area of bullet base) Now we're getting somewhere! Momentum is the integral of force over time (force is actually defined as the time derivative of momentum), so if we integrate both sides above by time (that is, integrate the pressure curve), then we get: momentum of bolt = momentum of bullet * (area of bolt face / area of bullet base) The area of a circle is of course pi * radius2, or pi/4 * diameter2, so this is equal to: momentum of bolt = momentum of bullet * (diameter of bolt face / diameter of bullet base)2 We can easily look up the momentum of a fired bullet. If we scale that by the area ratio, we get the bolt's momentum. If we divide by the bolt weight, we get the bolt's velocity. If we divide by a target bolt velocity, we get the required bolt weight.

ASSUMING a 4m/s bolt velocity is safe, then the required bolt mass is: bolt mass in pounds = 1.09x10-5 * bullet mass in grains * bullet velocity in fps * (diameter of bolt face / diameter of bullet base)2 The conversion constant 1.09x10-5 comes from asking Google to express 1 grain * 1 foot/second / 4 m/s in pounds. Here's the above bolt mass figured for some common cartridges: Cartridge 22lr

Bolt weight Bolt thrust Bullet Velocity Caliber Base Units pounds 0.4

Proof

Kpounds 0.9

Grains Fps 29 1240

Inches Inches KPSI 0.223 0.224 31.2

32a

0.8

1.8

71

905

0.312

0.338 26.7

380a

1.1

2.4

90

1000

0.356

0.374 28.0

38special

1.3

2.5

110

945

0.358

0.379 28.6

9x19 Parabellum

1.7

4.6

88

1500

0.355

0.391 50.1

7.62x25 Tokarev

2.0

4.0

87

1390

0.312

0.387 44.5

40s&w

2.2

4.9

135

1324

0.400

0.424 45.5

357magnum

2.2

5.0

125

1450

0.358

0.379 57.2

45a

2.3

3.7

200

975

0.452

0.476 27.3

9x23winchester

2.4

5.4

125

1450

0.356

0.392 58.5

45colt

2.4

2.9

185

1100

0.456

0.480 20.8

45gap

2.5

4.1

185

1150

0.452

0.476 29.9

357sig

2.6

5.6

125

1368

0.355

0.424 52.0

10mm

2.8

5.3

170

1340

0.400

0.425 48.8

410bore

2.8

2.4

109

1755

0.410

0.478 17.6

30 carbine

3.2

4.0

100

2200

0.308

0.356 52.0

44magnum

3.8

5.9

210

1495

0.432

0.457 46.8

454casull

5.4

10.2

240

1916

0.458

0.478 74.1

500s&w

5.5

11.0

275

1650

0.500

0.530 65.0

50ae

6.0

8.1

300

1579

0.500

0.543 45.5

7.62x39

6.3

6.9

123

2350

0.311

0.443 58.5

6.8spc

6.6

8.2

85

2900

0.268

0.421 76.7

223 Remington

7.0

6.9

80

2869

0.224

0.376 80.6

30-30

7.2

6.4

150

2390

0.309

0.420 59.8

7.7arisaka

9.9

8.3

180

2200

0.311

0.473 61.1

45-70

9.9

6.4

400

1900

0.458

0.504 41.6

308 winchester

11.3

10.8

168

2680

0.308

0.470 80.6

8mm Ma

11.8

9.9

198

2625

0.324

0.470 74.1

7.62x54R

12.2

10.5

180

2575

0.311

0.485 74.1

7mm Ma

12.3

10.0

154

2690

0.285

0.472 74.1

50alaskan

12.6

8.3

450

2150

0.500

0.548 45.5

30-06

12.8

10.4

190

2700

0.309

0.470 78.0

375h&h

14.2

12.8

235

3000

0.375

0.513 80.6

300wsm

17.4

15.7

150

3300

0.308

0.555 84.5

300 winchester magnum 17.8

13.2

190

3150

0.309

0.513 83.2

338lapua

24.4

18.4

250

3000

0.338

0.587 88.4

300lapua

25.0

18.4

220

2910

0.309

0.587 88.4

50bmg

54.3

27.4

660

3080

0.511

0.804 70.2

20gauge

5.5

4.6

218

1800

0.615

0.699 15.6

16gauge

7.7

5.0

350

1600

0.662

0.746 15.0

12gauge

9.4

7.2

437

1600

0.729

0.812 18.2

10gauge

12.9

6.3

765

1280

0.775

0.855 14.3

Kpounds

Grains Fps

Units pounds Cartridge

Inches Inches KPSI

Bolt weight Bolt thrust Bullet Velocity Caliber Base

Bolt weight = 0.5* (V / Sv *Eb) * (bW / 7000)

Proof