Methods of measuring barrel pressure

Assuming that the weapon is in good condition and that the correct type of ammunition is being used, it is the pressure produced in the barrel which ultimately decides whether the bullet will either reach the muzzle, exit from the barrel at an acceptable velocity or destroy the weapon completely.

Homemade Guns And Homemade Ammo

Figure 3.1 Pressure barrel.

Often weapons are received with reloaded or home- made ammunition and for safety sake, it is often necessary to determine whether the ammunition is in fact safe to fire. At other times, it is necessary to evaluate the suitability of an ammunition/weapon configuration and once again knowing the barrel pressure produced could be advantageous.

A knowledge of the basic facts concerning how the pressure is measured and what the figures mean is therefore a useful adjunct in this field.

The measurement of maximum chamber pressure is carried out with a 'pressure gun'. This is a very strongly built action and barrel with a hole drilled into the top of the chamber. Clamped over this hole is a closed tube with a free-moving piston (Figure 3.1).

Between this piston and the closed end of the tube is inserted a small disc of metal of a known and uniform hardness. On firing the cartridge, the pressure produced forces the piston up against the metal disc which is crushed against the closed end of the tube. Crushing the metal disc in this way reduces its thickness by a measurable amount. By subjecting similar discs to known pressures, it is possible to calculate the pressure of any cartridge by measuring the compression of the disc.

As no single metal will give consistent results over a wide range of pressures, discs made of lead and copper are used. The lead discs are for lower-pressure cartridges and the copper discs for cartridges producing higher pressures.

As the discs only give accurate pressure figures over the mid part of their range, they cannot be accurately related to actual pressures in pounds per square inch or kilograms per square centimetre. As a result of this, the results are referred to as ' lead or copper units of pressure' .

In more modern pressure guns, the metal disc is replaced by a small quartz crystal. This crystal will, when subjected to pressure, produce a tiny quantity of electricity which can be directly related, with great accuracy, to the pressure exerted upon it. These are called ' piezoelectric' pressure guns. The pressures

Table 3.1 Some illustrative chamber pressure figures for modern ammunition.

Cartridge

Velocity (ft/s)

Bullet weight (gr)

Pressure (psi)

0.22" LR

1200

40

15 300

0.32" ACP

960

71

21 700

0.38" Special

650

148

21 700

9 mm PB

1200

125

35 500

0.45" ACP

855

234

14 000

5.56 mm M16

3250

56

52 000

12B Shotgun

2.5" Cartridge

1200

490

10 000

measured with these guns are referred to in pounds per square inch or kilograms per square centimetre and are absolute figures (Table 3.1).

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Responses

  • makda
    How to measure barrel pressure?
    4 years ago
  • togo
    How to mesure pressure barrel?
    3 years ago
  • Erik
    How do you measure a firearms chamber pressure?
    2 years ago
  • david
    How to produce pressure in the gun barrel?
    2 years ago
  • pierina
    What are the methods in measuring barrel pressure?
    1 year ago
  • berenice
    How cartridge pressure is measured?
    1 year ago
  • Letteria Lombardi
    How bullet pressure is measure?
    1 year ago
  • zewdi
    How is gun barrel pressure measured?
    12 months ago
  • JOHANNA
    How to calculate muzzle pressure?
    2 months ago
  • Eugenio
    HOW TO FIGURE BARREL PRESSURE?
    2 months ago
  • bellisima
    How to calculate barrel pressure?
    2 months ago
  • brody christie
    How to determine muzzle pressure in a firearm?
    22 days ago

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