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Old 23rd April 2010, 03:49 PM
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Scoch Scoch is offline
Join Date: Sep 2009
Member of: Tayside Airgun Club
Location: Dundee, Scotland
Posts: 556

Copied from elsewhere but always relevant, this is how your gun will be tested, I know because I have been in the Forensic firearms lab whilst they did it, they do not go out of their way to get max power just a standard test for consideration of court purposes:

Air weapons seized by the Police are checked for safety, (unloaded) and submitted for testing by a Home office approved and trained firearms officer. The first stage is an examination of the gun, recorded is its calibre, any serial number the make or manufacturer and the overall condition.

The tester has to in the first instance be able to successfully load and fire the weapon . He will for instance attempt to clear a blocked barrel, but his interventions are limited.

He is in possession of a variety of magazines and fill probes to cover PCP,s he also has at his disposal Co2 capsules and a wide range of pellets.

He also has available a calibrated Skan Mark 9 chronograph hard wired to a PC. He also uses a calibrated weighing scale. Both of these devices receive regular calibration tests.

The test shots are fired at a distance of one metre from the Skan chronograph.

The pellets he uses are normally of a good quality brand, I have seen Air Arms pellets used frequently, although the brand is not identified in his report.

He then proceeds to weigh five of each different brand of pellet, pre selected for their known propensity to be either light weight, medium weight or heavy weight.

The ambient temperature of the test site is recorded

The gun is loaded and each of the string of five shots is fired through the chronograph, ( this part of the test is not recorded) although the velocity appears on the screen of the PC. He then identifies which string of shots gives the most consistently high power.

( It should be mentioned here that light weight pellets are more prone to being over the limit in a spring gun, whilst a PCP generally produces higher readings with heavy weight pellets).The tester is obviously familiar with the power out put of various types of air weapons with regard to their construction & operational capacities.

Once he has established the highest output, he will then select ten pellets from that particular brand that gave high readings & proceed to record the velocity of each shot. Obviously what he is looking for are the shots that exceed the set limit, 12ft lbs for a rifle, 6ft lbs for a pistol.

He has discretion, but not much, if three or more shots in the fired string of ten shots exceeds the limit, his report will indicate a S1 firearm. Under 3 shots over the limit, he will mention this in his report, but not indicate that it falls into the firearms category.

I have listed a copy of how a log is presented, the weapon is fictitious, but the chart is genuine. Weapon tested Pistol, .177 Walther PPK, Co2 powered.

Weight (grains) Velocity (ft/s) Muzzle Energy (ft lbs)
7.30 381.69 2.36
7.30 368.90 2.21
7.30 374.49 2.27
7.30 351.95 2.01
7.30 349.19 1.98
7.40 343.08 1.93
7.40 348.09 1.99
7.40 337.52 1.87
7.40 330.98 1.80
7.50 303.00 1.53

Mean velocity = 348.90 ft/s - standard deviation = 21.77

Mean muzzle energy = 2.00 ft lbs - standard deviation = 0.23.

The uncertainties in calculations shown above are for a confidence of not less than 95%

From the above graph it can be seen the pistol falls below the power level of a standard 6ft lb pistol, so does not constitute a S1 firearm and is not subject to the provisions of the Firearms (dangerous Air weapons) rules 1969 & as such does not require a firearms certificate. However, it does fall within the remit of a lethal barrel weapon, case law is used to decide this principal based on the following :

An air weapon, upon firng has to produce sufficient energy at the muzzle to have a “lethal potential” on humans.

This is based on the fact that if a projectile has the ability to penetrate human skin and underlying soft tissue, it has the potential to cause more than a trivial injury from which death may result.

Case law has it, Minimal Velocities Necessary for the perforation of skin by airgun pellets , have determined that a .177 calibre air pellet would penetrate skin at a velocity of 245 feet per second (331 in .22).

Therefore the pistol as tested would fall within the category of a lethal barrel weapon.

Guns that fall below that level of power, are often referred to as BB guns, these do not escape censure, classification follows that it would have the appearance of a genuine firearm and therefore fulfils the criteria of an “Imitation Firearm” as defined by Section 57(4) Firearms Act 1968.

There are many circumstances that the Police become involved in the seizure of guns.

One such scenario for instance, a person has his air rifle seized by the police for testing, following his car being stopped by the police with a gun in the boot.
The gun owner believes that his gun conforms to the law, but has no means to test it.
Following a test the air rifle shows four shots at 12.50 ft lbs. From this point a file of evidence is submitted to the CPS or Procurator Fiscal in Scotland for advice on the way to proceed. Critical factor considered by the CPS, are the circumstances & is it in the publics interest to proceed with charges?

The answer in this case is no, it would not be in the publics interest to prosecute, however, this decision would be based on the consent of the gun owner surrendering any right to the weapon. Legislation has it that once a weapon is tested over the limit, it becomes a S1 firearm, it cannot by law be returned to its previous status. If the owner decided to contest his right to own the gun, a case would then be prepared for court based on the evidence provided.

If a person is caught on land with an air weapon over or under the limit without lawful authority, taking pot shots at random targets, dogs, cattle etc, will invariably face a whole raft of charges as it would be without doubt within the publics interest to prosecute.

Now you know, personally its 770 to 777 fps for me using JSB 4.53
Steve CochraneWalther LG300, Leupold MK4
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