Home / Proof Marks / British proof — "NOT NITRO" / "BLACK POWDER"

British proof — "NOT NITRO" / "BLACK POWDER"

British proof marks · 1954 to today (the wording dates from 1954).
What it looks like
The words NOT NITRO or BLACK POWDER stamped in full, usually beside a proof mark.
Where it is on the gun
Barrel flats.
Date range
1954 to today (the wording dates from 1954).

What it tells you

What this mark authorises you to say

The gun is proved for black powder only. It is the single most safety-critical mark on a British gun, because it states what the gun may not be fed: this barrel has not been proved for smokeless powder, and shooting smokeless in it is not a marginal decision.

What it does not tell you

What this mark does NOT say

It is not a statement about the gun’s quality or value — many fine guns are black-powder proofed — and it is not permanent in the sense people assume. The gun can be submitted for nitro reproof, and on a Damascus-barrelled gun that is usually refused.

Sources for this page

Every claim above is attributed. The class of source is shown with each one, because a national proof house and an anonymous forum table are not the same evidence — and on proof marks the difference matters.

Related on this site

Makers whose guns carry marks like this:

Reading marks to identify and date a gun

Proof marks name the test and the era. The serial number, where a maker published a browsable chart, can name the year. The lookup cites the threshold behind every result.

Open the serial number lookup

Other british proof marks

Mark descriptions observed and verified 2026-10-14. Proof marks are stamped by hand on guns up to a century old; a photographed stamp and a description in a book are not the same evidence. If a mark on your gun does not match anything here, that is a real answer — see the notes on unidentified marks.