In the first of a new series, Gun Trade Insider explores the history, role, and process of the London Proof House. Proof Master David Miles explains how this centuries-old institution continues to safeguard firearm standards and uphold British gunmaking traditions.
For nearly four centuries, the London Proof House has played a critical role in ensuring firearm safety and quality in the United Kingdom. Established in 1637 by Royal Charter from King Charles I, it remains a fundamental institution in the British firearms industry. The Proof House enforces strict proofing standards, ensuring that every firearm bearing British proof marks has undergone rigorous testing and meets legal safety requirements.
At the head of this institution is Proof Master David Miles, who is responsible for overseeing the proofing of firearms, maintaining compliance with the Gun Barrel Proof Act of 1868, and upholding the long-standing traditions of the Proof House.
“The test first came about in the 1600s because back then, anyone could attempt to make a gun and sell it. There was no safety standard, so firearms were often dangerous to the user,” explains David.
“As a result, skilled gunmakers wanted recognition and a City Livery Company of their own to control the quality of gunmaking and the safety of firearms. In 1637, King Charles I issued a Royal Charter which set up the Gunmakers’ Company, which in turn set up a Proof House.”
The proofing process: Ensuring firearms safety
Proofing a firearm is not simply a case of firing a round through it. The process is designed to subject a firearm to extreme pressures to ensure that it can withstand the forces it will encounter in regular use.
“It’s a process of inspecting, gauging and firing overpressure ammunition through a firearm to stress test it. If the pressure-bearing parts (bolt, action, barrels) change, or it does not meet the measurement tolerances, the firearm fails the test. If it passes, it will be proof marked.”
At the London Proof House, the process involves several steps:
- Visual inspection – The firearm is examined for cracks, bulges, dents, and other structural flaws.
- Measurement and gauging – The chamber and bore dimensions are checked to ensure they are within tolerance.
- Overpressure testing – The firearm is fired using proof ammunition that generates 25-30 percent higher pressurethan standard loads.
- Post-firing inspection – The firearm is examined again to ensure there has been no material change in its structure.
“We proof fire, typically two rounds per barrel. We control the maximum pressures that ammunition can achieve, and from this our proof pressures are typically 25-30 percent higher. We use a secure, remote room where the gun is held in a jig and fired into a snail trap. After firing, we will headspace gauge again and conduct a second view. If the gun is out of tolerance, or if there has been any material change in the pressure-bearing parts, we label it as failed proof.”
If a firearm fails proof, it cannot be sold, exported, or transferred until it has been modified and successfully re-tested. If it passes, it is stamped with official proof marks, certifying that it meets the legal safety standards required for sale.
The legacy and importance of proof marks
Proof marks serve as an official certification of safety, ensuring that a firearm has successfully passed the testing process. These markings are recognised both domestically and internationally, adding credibility to firearms manufactured or imported into the UK.
“If it passes, then we apply our proof marks that indicate what pressure ammunition can be fired through the gun and include crucial dimensions of the bore. The London Proof House has applied the Crowned GP proof mark to all guns which have passed the tests since our Royal Charter of 1637. Next time you hold a British-made gun, have a look for it.”
The Gun Barrel Proof Act of 1868 reinforced the legal requirement for proof testing, making it illegal to sell or offer an unproven firearm. This Act, along with the Rules of Proof, ensures that firearms meet high safety standards before they enter the market.
David Miles: From law graduate to proof master
David Miles did not take a conventional path into the world of gunmaking and proofing. Initially studying law, he quickly realised that he wanted a career that took him beyond an office environment.
“After studying law, I realised I didn’t want a normal office job, so started looking for something I could be interested in. In early 2013, I came across an advert for a gunroom manager position at a gunmaker which had recently re-opened in London – John Rigby & Co.”
Through persistence, he secured the position and spent eight years at Rigby, working with some of the world’s most prestigious firearms. His experience even led to encounters with royalty and high-profile clients.
“One special memory is a customer, a member of a royal family, flying me over to their country to help zero their new rifle.
After several hours shooting guns with his top military officers in attendance, we went to one of the royal palaces for lunch with 15 members of his family. Another prominent family member stood up, took my plate and served me heaps of succulent, spiced lamb. That simple act of service, from a man who had such a high position and power, was a lesson in humility, class, and hospitality that I won’t ever forget.”
His career path ultimately led him to the London Proof House, where he now serves as Proof Master, carrying forward centuries of firearm safety traditions.
The future of the London Proof House
While the London Proof House remains steeped in history, its role is as relevant as ever. Every firearm imported, manufactured, or sold in the UK must undergo proof testing, ensuring safety for users and maintaining the integrity of British gunmaking.
“The Royal Charter (and the Gun Barrel Proof Act of 1868) gives us authorisation to seize guns if we believe someone is selling unproven guns and requires anyone selling a gun to ensure it is proven and in proof.”
As the firearms industry continues to evolve, the London Proof House remains a vital institution, preserving British craftsmanship while upholding the highest standards of safety.
Next in the series
In upcoming instalments of this series, Gun Trade Insider will explore the technical aspects of modern proofing, the impact of changing legislation on UK gunmakers, and further insights from Proof Master David Miles.
For retailers, distributors, and manufacturers, understanding the role of proofing in the firearms trade is essential. Future articles will highlight how proofing impacts sales, exports, and consumer confidence, ensuring that every firearm on the market meets the highest standards.
Get in touch
T: 02074812695
E: proofmaster@gunmakers.org.uk
W: https://www.gunproof.co.uk/
You can read the full April 2025 issue below:
