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The Proof Master
The Worshipful Company of Gunmakers
London Proof House
48 C1 1LP

"Small arms" includes explosive-operated small arms of every description, whether of present use or future invention, adapted for the discharge of shot, bullet or other projectile. Such arms include shotguns, rifles, pistols, revolvers, cattle killers, line throwers, signal pistols, alarm guns and nail driving or other industrial tools.

Purpose and brief history

Proof is the compulsory and statutory testing of every new shotgun or other small arm before sale, to ensure so far as is practicable, its safety in the hands of the user.

Reproof is the similar testing of a small arm which has previously been proved. Both necessarily involve the firing through the barrel of a considerably heavier load than is customary in the shooting field, thereby setting up pressure and stress on barrel and action much in excess of the pressure generated by standard load cartridges. Such pressure should, and is intended, to disclose weakness in guns, whether new or used. For it is preferable that weakness be found at a Proof House rather than in the field, where personal injury may result.

Proof in Great Britain dates back to 1637, when the Gunmakers Company of London was granted its Royal Charter. Proof was necessary to protect the public against the many unsound arms then being made and sold, which not only endangered the public but, indirectly brought discredit upon reputable gunmakers.

The Gunmakers Company secured its Ordinances in 1670 and from that time was enabled to enforce proof in and around London. The original proof marks are still in use today.

The Birmingham Proof House was established for public security in 1813 by Act of Parliament, requested and obtained by the Birmingham Gun Trade at its own expense. At a considerably earlier date private Proof Houses were in use in Birmingham. Marks similar to those used at one of them controlled by the gunmaker "Ketland", became the first proof mark of the officially established Birmingham Proof House.

Since 1813 it has been an offence to sell or offer for sale an unproved arm anywhere in the United Kingdom.

These pages are intended to give the information most likely to be required by those owning or interested in the purchase or sale of shotguns and other small arms. They do not claim to be, neither are they intended  to be a complete encyclopaedia on the proof of guns or of all the proof marks available.

The law

The present law on the subject is to be found in the Gun Barrel Proof Acts 1868, 1950 and 1978 and various Rules of Proof, but particularly those of 1925, 1954, 1986 and 1989, when the metric system of measurement was introduced. Copies of the several Acts and of Rules of Proof of 1989 may be obtained from either Proof House, details of which appear at the end of these particular pages. The maximum prices per barrel, which may be charged for proof, are set down in the Gun Barrel Proof Act of 1950 and subsequent statutory orders.

The Proof Acts

The provisions of the Acts apply to all small arms, whether of present use or future invention, within certain fixed limits of bore size and projectile weight (with the exception of some military arms made for the use of H. M. Forces ). Air guns, not being "firearms", are specifically excluded.

The Proof Acts lay down that no small arm may be sold, exchanged or exported, exposed or kept for sale or exchange or pawned unless and until it has been fully proved and duly marked. The maximum penalty is 1,000 for each offence, but with provision for higher penalties where, for instance, the sale of a number of guns constitutes one offence. Alteration to or the forging of proof marks is a still more serious offence.

Arms previously proved and bearing apparently valid proof marks are deemed unproved if the barrels have been enlarged in the bore beyond certain defined limits or, if the barrel or action has been materially weakened in other respect.

The offence of dealing in unproved arms is committed by the seller and not by any unwitting purchaser.


The importation of unproved arms into the United Kingdom is subject to control as prescribed in Section 122(4) of the 1868 Act, as amended by the Act of 1978.

Notification of importation has to be given to the Proof House within seven days and/or the arms submitted to proof within twenty eight days of arrival in this country.

These regulations do not apply to small arms imported by any person for his own personal use, while they remain his own property. Penalties for offences are similar to those for the sale of unproved arms.

Foreign proof marks

Prior to June 1980, there was reciprocal agreement for recognition of certain foreign proof marks, by international accord. At that time the United Kingdom became a signatory member of the International Proof Commission (C.I.P.), Secretariat, at the Belgian Proof House, Liege. Since then the United Kingdom has recognised all the proof marks of the other member nations and, reciprocally, they all recognise UK marks. The C.I.P. has been working since 1914 for the standardisation of proof, which also involves standardisation of pressure measurements, of chamber and bore sizes and cartridge dimensions.

Currently its members are: Austria, Belgium, Chile, Finland, France, Germany, Hungary, Italy, Russia, Spain and the United Kingdom.

Previous reciprocal agreement continues with the Republic of Ireland as it is not a member of the C.I.P.

It should be borne in mind that all countries have made changes in their proof marks from time to time and it is not practical to include within these pages all the proof marks that have been used over many years.

It should also be observed that proof in France was optional until 1960 and there have been marks impressed by some French gunmakers, which appear to the layman, to be official proof marks, but are not.

Additionally there were proof marks used in Austria, Germany and Italy which were valid in this country before and up to the outbreak of World War ll, but which are now invalid and have been replaced by new marks. Care must be taken in differentiating between the old unacceptable marks, and the newer valid type.

A book containing all the currently valid, foreign and UK proof marks, is available at a small charge from the London and Birmingham Proof Houses.

In general the importation of foreign arms, bearing no proof marks or bearing marks not now recognised is an offence, unless those arms are submitted to a Proof House within 28 days of arrival. The sale of such guns unproved would constitute a further offence. This warning applies particularly to arms made in countries where there are no official Proof Houses.

Rules of proof

Rules, Regulations and Scales of Proof, a schedule to the Proof Act, are the working instructions of the two Proof Houses. The Rules specify the pressure to be used in proof, standards of view and the marks to be impressed on guns which pass proof, together with such detail as bore and chamber dimensions, proof and service pressures.

The latest Rules of Proof, those of 1989, were approved by the Secretary of State, to come into force on 1st November 1989. However, proof under earlier Rules of 1875, 1887, 1896, 1904, 1916, 1925, 1954 and 1986 remain valid provided that the barrel or action has not been materially weakened or altered so that it no longer conforms with that proof mark.

Black powder guns

Many shotguns proved under Proof Rules before 1904, when the nitro proof marks were introduced, and some shotguns proved before 1925, when nitro proof became compulsory, were proved only for use with black powder.

Such guns will not bear any of the nitro proof marks. It should be clearly understood that, whilst such guns may be proved for black powder, they are unlikely to be legally proved and must be deemed unsuitable for use with present day cartridges, until they pass a nitro proof test.

Types of proof

There are two main types of proof:

Provisional proof in general applies only to shotgun barrels in an early stage of manufacture and is designed to prevent the maker continuing work on defective tubes.

Definitive proof applies to all arms and is effected either in the "white" or in the finished state.

Additionally there is a special proof to cover loads developing pressures in excess of normal service loads. This can be either as a voluntary proof, to satisfy a particular requirement, or as a compulsory proof where the arms are designed for unusually heavy loads

Proof for steel shot

In 1993 a C.I.P. specification was adopted covering special proof for guns which can be used with steel shot. The specification lays down shot size and hardness, the number of proof rounds to be fired through each barrel and the pressure to be generated at 25mm and 162mm. A special "Steel Shot" proof mark will be stamped on each barrel of such weapons that have successfully been proved.


Reproof, or the further test of a gun after its original proof, may be necessary for a variety of reasons, of which the main ones are:

  1. Indications of weakness in action or barrel, including cracks, pitting, bulges, dents or failure of the brazing of the lump.
  2. Potential weakening, such as by conversion to ejector, repair of the action or barrel by welding, electrolytic deposit of hard chrome or other metal in the barrel.
  3. Enlargement of the internal diameter of the barrel, or lengthening of the chamber so that it no longer conforms with the existing proof marks.
  4. Replacement of action, barrel, barrel lug or extension.
  5. Fitting of any attachment, such as a variable choke, which must withstand the pressure of firing.
  6. Present inadequacy of earlier proof. Black powder proved guns, most commonly proved over 90 years ago, may not be safe for use with smokeless cartridges and require reproof for nitro powders.

If mishandled or neglected, a gun may be damaged or weakened, even in a short period of service. In such circumstances work necessary to return it to serviceable condition, may render invalid the original proof marks.

Indications of weakness may only be apparent to those trained to recognise them. For that reason, inspection of guns by a gunmaker, at regular intervals, is recommended, and advice to submit for reproof should be followed without delay to avoid undue risk of personal injury.

Guns are submitted to reproof at the owner's risk and the gunmaker is entitled to payment for his work, regardless of the result of proof. Guns will not be accepted for reproof, if it is the decision of the gunmaker that they are not in a fit condition to be proved.


Submission to proof

Any individual may submit arms for proof or reproof direct to either of the two Proof Houses, but it is more usual, and generally more satisfactory for all concerned, that arms be submitted through a gun dealer. Primarily this is because the majority of old guns require attention prior to proof.

Proof Regulations require that shotgun barrels shall be "struck up" and smooth and that insides shall be clean. Pitting should be removed so far as is practicable, bulges knocked down and dents raised. Actions should be in good safe working order and tight on the face to resist the increased strain of proof pressure. Since stocks, and particularly those with unusual "bend" or "cast", are not designed to withstand the heavy recoil of proof, it is customary for the wood to be removed. Indeed, the Proof Houses do not accept responsibility for damage to stocks resulting from proof.

It will be apparent that to fulfil these requirements, the preparation necessary will best be undertaken by a gunmaker who is accustomed to submitting to proof.


In the event of a proof rejection, or failure to withstand the proof test, guns may be repaired and resubmitted. On final rejection, that is when the submitter accepts that further attempts at repair are unlikely to succeed, the existing proof marks upon the barrels and/or action will be defaced or barred out.

It is unlawful for a weapon to be sold with defaced proof marks, except where later reproof marks have been impressed. It is recommended that such guns be deactivated, so as to ensure that it can never be used by some person unaware of its unproved condition.

Memorandum on black powder guns

Up to 1887 there was provision only for the proof of guns for black powder; but by that time the use of smokeless or nitro powders was commonplace. In that year a proof to cover their use, supplementary to definitive proof, was introduced. The service load of the powder intended for use, i.e. E.C. or Schultze, was then impressed on the barrel at proof. Under the 1896 Rules, proof to cover the use of nitro powders was still supplementary to the ordinary proof for black powder, but the words "Nitro Proof" were introduced as a proof mark.

The NP marks were introduced in 1904 but the nitro proof test remained optional until 1925, when new Rules of Proof made it obligatory. By that time most gunmakers had been voluntarily submitting their guns to nitro proof for many years.

Except on guns proved since February 1955 the NP marks were always used in conjunction with the words "Nitro Proof". The black powder proof marks remain valid, and a gun bearing them may still legally be used with black powder cartridges, provided it has not undergone any alteration taking it out of the category and state in which it was originally proved. Such alterations include conversion to ejector, rebrazing the lumps, increasing the depth of the chambers to take a longer cartridge or the enlargement of barrels beyond certain defined limits.

A gun, through neglect or misuse, may become unsafe even in a short time, and a gun made over fifty years ago may be extremely dangerous.

Shooters are therefore urged most strongly to buy only guns bearing the marks of nitro proof and not to permit the use of nitro or smokeless cartridges in any black powder gun already in their possession, until it has passed the nitro proof. If owners wish to use such guns with nitro powders, they should send them to their makers, other gun firm or gunmaker for advice, estimate for preparation in accordance with the Rules of Proof, the carrying out of such work, and submission for nitro proof.

The charges involved must of course be paid whether or not a gun passes the proof test, but it is better that any weakness be revealed at the Proof House rather than in the field.

Muzzle-loading and black powder proved guns may be reproved for black powder. It will hardly be necessary to point out to members of the gun trade that neither their own interests nor those of their customers can be served by the sale of black powder guns which may have become dangerous. For many years some firms have not sold black powder guns and, in addition, will not do any work to such weapons except preparation for and submission to proof.

Such a policy may not be possible in all cases, but apart from any question of legal liability for repairs carried out, it is urged that there is a heavy moral responsibility to point out the age and condition of any of these veteran guns before accepting them for repair.

Muzzle-loading arms should never be fired with nitro powders.

The sale at auction of shotguns and small arms

Care should be taken in accepting small arms for sale, because under the Gun Barrel Proof Acts of 1868 to 1978, it is an offence to sell or offer for sale by auction or otherwise, any small arm, i.e. shotgun, rifle, revolver, pistol or other firearm, unless it bears lawfully impressed and valid proof marks.

Caveat emptor does not apply if the arm is unproved. It must be emphasised that the sale of unproved arms between auctioneers and registered gunsmiths or dealers, is as much an offence under the Act as is the more obvious offence of selling an unsafe and unproved gun to a member of the public.

The Act makes no distinction between trade, auctioneers and the public. The offence is absolute!

All arms made in Great Britain are proved and marked at either the London or Birmingham Proof Houses prior to sale to the public. Valid proof marks of certain other countries with which reciprocal agreements are in force, also legalise sale in this country.

All ex-military arms proofed by the Government Arsenals must pass the civil proof tests, prior to sale to the public. Following privatisation of small arms manufacturers in 1982, all small arms were subject to proof by the British Proof Authorities and do not require reproof.

There is no provision in Proof Regulations to permit the sale of unproved arms as ornaments, nor is there any exemption for antiques

Used small arms, particularly shotguns, may appear properly proved and marked, but may have been weakened and the proof marks rendered invalid, by enlargement of the bore to remove rust or pitting or by other material alterations. This is not uncommon. Special equipment and knowledge of the subject are necessary to determine whether proof marks are valid or otherwise.

The advice of the Proof Authorities as to the disposal of guns bearing proof marks, where barrels are beyond repair, (and it is understood that this is already the practice in many auction sales specialising in arms), is that the stock, action and fore-end may be sold, but the barrels may not.

Where the barrels are repairable and can be reproved, this must be done prior to sale.

A certificate is available, on payment, from either Proof House for guns which are not to be used, as for example antiques or collectors items, which cannot be proved, as where no ammunition is available.

An increasing number of complaints is being received, of the unlawful sale of small arms at auction - at times in condition dangerous to the user. Recommendation is made that auctioneers take expert advice before offering small arms for sale. The Proof House will give every reasonable assistance but must warn that they will institute proceedings where offences are considered to justify such action. The auctioneer, the owner of the arm and the person submitting the arm to auction bear equal responsibility at law.

Notes on the purchase of second hand shotguns

The purchase of a second hand shotgun involves somewhat similar risks to those incurred in the buying of a second hand motor-car, or an expensive second hand watch. Each to a degree is the product of  skilled craftsmen, and in none is it a simple matter for the layman to detect every defect or weakness.

To suggest that one should go to a reputable gunsmith or dealer and buy the best gun one can afford may be sound advice, but it is cold comfort to those who really cannot afford a good second hand gun or to those who may be tempted to purchase a second hand gun from an acquaintance, in the market place, at auction or sale room or even at the local tavern.

When contemplating the purchase or sale of a used gun, check must be made that the proof marks remain valid. Proof marks indicate the soundness of the gun when it was last proved, but the gun may have been so altered that it is unproved in its present state, although the proof marks remain.

The incidence of VAT on new guns added to their already high cost. This has placed a premium on the better class of second hand guns so that there are many cheaper, old guns being offered for sale, which in more normal times, would have been considered past further service.

Where purchase is contemplated from sources other than reputable gunmakers, gunsmiths or dealers, it is suggested that the gun be submitted to a reputable gunmaker for report on its condition prior to completion of the transaction. Where difficulty is experienced in obtaining such a report, request may be  made to one of the Proof Houses for advice as to whether or not the gun is or is not in a fully proved condition. However, the Proof House should not be expected to advise as to mechanical condition, quality or value.

Adaptation of shotgun magazines

Section 1 (3) of the Firearms Act 1968, as amended by Section 2 of the Firearms (Amendment) Act 1988, defines the types of smooth bore guns which may be held on a shotgun certificate. It includes a smooth bore gun which has been adapted to have a non detachable magazine, incapable of holding more than two cartridges. In such a case the magazine must bear a mark approved by the Secretary of State, and the adaptation must be certified in writing, by the London or Birmingham Proof House, as having been carried out in a manner approved by him.

This adaptation is carried out on pump-action and semi-automatic, large magazine shotguns which, prior to the above Act, could have been legally held on a shotgun certificate. Unless the required adaptation is carried out, these weapons can now only be held on a firearms certificate.

The following show those proof marks, approved by the Secretary of State under Section 1 (3A) of the 1958 Act, for denoting that guns have been so adapted. The figures "89" relate to the calendar year and changes as appropriate.

Proof House
Proof House (1)
Proof House (2)

Deactivation of firearms

Section 8 of the Firearms (Amendment) Act 1988 provides that a firearm which has been certified by one of the Proof Houses as having been deactivated in a manner approved by the Secretary of State, and marked to that effect, shall no longer be regarded as a firearm.

Firearms so deactivated and proof marked, are no longer subject to any of the conditions or controls contained in any of the Firearms Acts or Rules.

The following show those proof marks, approved by the Secretary of State under Section 8 of the Firearms (Amendment) Act 1988, for denoting that guns have been so deactivated. The figures "89" relate to the calendar year and changes as appropriate.

Proof House
Proof House (1)
Proof House (2)

Services of the Proof Houses

The information within these pages form a small extract of the services available from the two Proof Houses. Advice on the following matters is also available:

The proof of guns for magnum cartridges
The use of welding in the repair of guns
The repair of gun barrels by the sleeving method
Information as to barrel enlargement and details of proof sizes
Information on pimple bulges in shotgun barrels

A comprehensive booklet is also available, at a small charge, on the "Proof of shotguns and other small arms". It contains details and illustrations of most foreign and British proof marks and would prove invaluable to the shooting enthusiast.

If you are in any doubt as to the condition of a firearm possessed, or intended for purchase by yourself, the Proof Houses are there to help you. A gun may have a number of faults not apparent to the inexpert eye. Examination by the Proof House can determine:

Whether the gun has been proved, bears the relative marks and is suitable for use with modern cartridges
Whether the bores have been enlarged since the barrels were last proved, and if so to what extent
Whether the barrels are in good condition generally, i.e. free from rust, pitting, dents and bulges
Whether the chambers have been altered to accept a longer case since the gun was last proved
Whether the action is "off the face" of the barrels or otherwise loose
Whether the action is in good safe working order
Whether the gun patterns well at normal distance

It is regrettably true, and commonplace, that there are guns offered for sale by irresponsible persons which would not pass examination satisfactorily on any one of the points listed above. Such a gun may well be unproved, unsafe and expose any user and nearby spectator, to extreme danger.

The shooting public are given protection by the Gun Barrel Proofing Acts of 1868 to 1978. The Proof Authorities and the Proof Houses were established for public security and closer co-operation between the shooting public, gunmakers and the Proof Authorities must result in a reduction of the risks involved in the purchase of second hand shotguns and small arms from chance acquaintances, unscrupulous dealers or misinformed friends.

British Proof Authorities


The Worshipful Company of Gunmakers of the City of London,
The Proof House, 48 Commercial Road, London, E1 1LP
Tel: 020 7481 2695
Fax: 020 7480 5102


The Guardians of the Birmingham Proof House,
The Gun barrel Proof House, Banbury Street, Birmingham, B5 5RH
Tel: 0121 643 3860
Fax: 0121 643 7872

Further information can be obtained directly from the Birmingham Proof House Web-site: www.gunproof.com

Send mail to cdrpc@btconnect.com with questions or comments about this web site.
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Chesterfield And District Rifle And Pistol Club
Last modified: May 03, 2016