WARNING!  Sound moderators incorrectly marked by the London Proof House

We strongly advise that any British proof marks on Reflex Suppressors should be treated as potentially misleading and possibly dangerous. If in doubt as to the suitability of a suppressor for your rifle, please refer to the technical guidance on this website or contact us directly for advice... (more info)

NEW!   Counsel's Opinion on the laws of Proof relating to sound moderators and other muzzle attachments

Counsel has confirmed that the October 2001 pronouncement made by the British Proof Authorities is "misleading and wrong in law"... (more info)

Proof testing of rifles and/or suppressors in the United Kingdom - legal and technical considerations

A. Summary and recommendations

B. Background

A. Summary and recommendations:

1. In the absence of any court decision to the contrary, we are advised that a suppressor or sound moderator, which is a freely removable accessory, designed to be interchangeable between weapons of different types and calibres, ought not to be considered to be a "part of a Small Arm". Such an accessory is not liable to fall within the definition of a "Barrel" in the Gun Barrel Proof Act 1868. We note, however, that the English proof houses have expressed a different opinion which is consistent with their own interests as private companies.
2. Whether or not a suppressor is really a "Barrel" for the purposes of the Proof Acts, there can be no legal requirement to submit any "Barrel" for proof unless and until it is fitted to a Small Arm which is to be sold, exchanged or exported, etc. There is no offence in the Acts of selling an unproved "Barrel" on its own.
3. Similarly, there can be no UK legal requirement to submit muzzle-threaded rifles for re-proof unless/until the entire rifle is to be sold, exchanged or exported.
4. In view of the wide range of firearm types and calibres (even air guns) to which reflex suppressors can be fitted, submitting bare suppressors for proof before sale would not be practical.
5. Reflex suppressors are produced in a CIP country by Europe's largest manufacturer of high-power rifle suppressors.
6. Noting that non-CIP countries like Switzerland and the USA manage very well without compulsory proof, we conclude that CIP proof is no substitute for modern workshop quality assurance procedures.
7. Although a number of suppressors have been proof-marked by the London Proof House for calibres larger than the baffle hole diameter, we warrant that firing an appropriate CIP proof cartridge through a correctly-fitted reflex suppressor will not harm it in any way.
8. In principle, we neither recommend nor advise against the proof testing of rifles after they have been fitted with reflex suppressors.
9. In the past, some perfectly good rifles have destroyed due to incorrect proof loads or other errors. Other rifles have suffered the sort of minor or latent damage which is to be expected when a vital component (the cartridge case) is subjected to an unknown pressure at or above its yield stress. Subject to our warranty given in point 7. above, any proof or re-proof is carried out at the owner's risk, particularly with regard to any possible loss or damage to the rifle.

B. Background:

On 31 August 2000, the London and Birmingham Proof Houses issued a circular entitled "Screw cutting of rifle muzzles and the fitting of sound moderators and other items". A further circular entitled "Conversion of Barrels and the Fitting of Muzzle Accessories" was issued by the Proof Houses in October 2001.

The contents and inferences of these circulars have been hotly disputed by the gun trade, and we consider that they are misleading to the extent that they convey the impressions:

(a) that there may be a legal requirement to submit all sound moderators for proof and,

(b) that there may be a legal requirement to submit all rifles for proof or re-proof after the cutting of an external screw thread at the muzzle.

Section 122.(3) of the Gun Barrel Proof Act 1868 ("the 1868 Act") creates an offence of selling or exchanging, or attempting to sell or exchange, a Small Arm the Barrel or Barrels of which are not duly proved or marked as proved.

However, the terms "Small Arm" and "Barrel" are separately and distinctly defined in the Act and from these definitions it is clear that there is no offence of selling, etc. an unproved "Barrel" on its own. Therefore, even if sound moderators were deemed to be "Barrels" as defined by the 1868 Act (a suggestion which is hotly disputed), there is no legal requirement to have them proved unless they are sold as part of a "Small Arm".

Similarly, with regard to the cutting of a screw thread on a rifle muzzle (or for that matter any other repair, replacement or modification of a Barrel), there can be no offence committed unless or until the entire Small Arm is subsequently offered for sale, exchange, export etc. Even if/when this were to happen, the requirement to submit a barrel for re-proof only arises if the barrel has been "unduly reduced in Substance or Strength".

As professional engineers, we reject any suggestion that a threaded rifle muzzle with a factor of safety against failure of more than four (as in the extreme case of a 1/2" UNF thread on a typical 7.62 mm rifle) is "unduly reduced in Substance or Strength", just as similar suggestions were dismissed in written evidence for the case of Regina v Beatham (see R-v-Beatham_evidence.pdf - 986 kB Adobe Acrobat file). We note that on receipt of this evidence, the Crown abandoned its case and the Defendant was duly discharged with his costs awarded from the public purse.