Proofing The Guns: London Proof House

Unlike in the United States, Britain requires that every single firearm imported, produced, or modified on the isle to be “proofed”. This means that at least two high-pressure charges be fired through that firearm before it can be allowed for public sale or usage. Proofing has been an official regulation since the 1600s when numerous Gunmakers put their heads together and asked that a standard be set for their industry. The problem they were trying to solve was that there were too many inconsistencies within firearms of the period and customers were suffering from this through improperly made guns. Today Britain follows the CIP standards set forth by a number of European countries. In the United States we have SAAMI which although is very similar, it isn’t government sanctioned as CIP is.

One of the fascinating things about the Proof House is that the work they do really hasn’t changed since 1637. Taking in a firearm or barrel at a time, proofing it, and sending it back out has been the business’s bread and butter for over 300 years of existence.

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Transcript ….

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Infantry Marine, based in the Midwest. Specifically interested in small arms history, development, and usage within the MENA region and Central Asia. To that end, I run Silah Report, a website dedicated to analyzing small arms history and news out of MENA and Central Asia.

Please feel free to get in touch with me about something I can add to a post, an error I’ve made, or if you just want to talk guns. I can be reached at


  • Marv

    It is the same in Germany. And CIP goes beyond just European countries.

    • Anonymoose

      I like the little antler thing on all HKs and Walthers.

      • USMC03Vet

        So many markings it’s like an ancient aliens episode on history channel.

      • john huscio

        Or the scorpion/twisty circle thing on German SIGs

      • TomT

        Beschussamt Ulm.

  • iksnilol

    I was hoping they’d poke the gun with their finger and go “yup, that’s definitely a gun, consider it proven”.

  • codfilet

    Even my WW2 Mossberg .22 rifle was proofed when it was sent to England for Lend-Lease.

    • RSG

      Wait… mean to tell me that EVERY ww2 firearm we sent to Britain during ww1 and 2 was proofed? Can’t be. There were 100’s of thousands. And during 2, they were pressed into service as fast as humanly possible.

      • codfilet

        It’s got British Proofmarks on it…..

        • Tom – UK

          Yes but does it have a date on it? Could be it was proofed after WW2

      • kyphe

        Generally speaking If it does not have a proof mark it was not in British service. Britain proof marked millions of small arms during WW2 both domestic and imported arms. There are some exemptions to the proof marking rules of 1925 for small arms in place relating to the British armed services, but even then you will never see such an example in private hands as the firearm could not be released out of service without being proofed first.

  • Maxpwr

    The part I like about England is how they proof their guns they will later confiscate from their subjects in the name of public safety.

  • jerry young

    Ours may not be marked but every new gun I’ve bought over at least the last 10 years has a little envelope in the box with a fired round in it with the exception of a gun I won in a raffle, that may not be done to Proof our guns but the manufacturer fires every gun, so what it doesn’t have a proof stamp on it that just means we have a little less government over reach it’s bad enough every liberal out there wants to take away our rights why should we have to pay an extra fee for those rights.

    • USMC03Vet

      That’s a crime thing so they have ballistics on file if the authorities come knocking.

      • Rick O’Shay

        Voodoo science. The point is moot the moment you get a new barrel or firing pin. I get that some states require it and take the spent casing and keep it on file, but I’m not sure anyone could prove a crime has been solved that way.

        • Marcus D.

          Such collections, such as the one in NY, are a dying breed, as they have failed to be used even once in a successful prosecution. Weapons chambers are too uniform and the science inadequate to prove that any given casing came from a particular gun. This is the deficit the various “microstamping” proposals are trying to remedy. So far, only one state (California) has passed a microstamping law, but since there is no technology available that reliably microstamps casings, there are no manufacturers building weapons that leave such markings.

      • jerry young

        It also show they fired it I’ sure if the gun didn’t work properly they wouldn’t sell it, having some law enforcement background I already knew this, some states require the FFL to log that casing and you don’t get it when you purchase a gun not where I live.

    • The Rambling Historian

      Definitely not the same as proofing. When you proof a gun you fire an specially formulated hot load to check integrity. The weapon is inspected before and after the test to see if damage was done.

      • jerry young

        I know that but still it shows the gun had been tested maybe not at certain high pressures but still tested, and I prefer not firing a hot load just to see if my gun can handle it and certainly don’t want another stamp on the guns I own and definitely don’t want any more government regulations

  • Stephen Paraski

    Plumbers & Gas Fitters have been around a long time in London too.

  • Jaedo Drax

    There are a lot less proof houses than there were, a long time ago there was a tower proof (civilian) house.

  • WFDT

    My 1911, made in 1918, bears both “US PROPERTY” and marks from the London Proof House.

  • Marcus D.

    The Italians have their own proofing houses also. My Colt clones all bear proof marks, and many have manufacturer’s house marks as well.

  • survivor50

    Can we get a “Proof House” for politicians???

  • kyphe

    A little etymology. The word Proof or Prove originally meant “Test”(neutral) rather than “Confirm”(Positive) as we use in modern parlance. So the old saying “the exception proves the rule” means the exception tests the rule not confirms it. Now the proof mark is evidence that confirms the quality of the barrel which is one reason we now use the word proof to mean evidence of conformation. Basically firearms history affecting every day language.

  • CavScout

    Criminal institution.