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"Nitro Steel" / "Smokeless Powder Steel"

Barrel steel markings · About 1900 to the 1930s.
What it looks like
The words NITRO STEEL or SMOKELESS POWDER STEEL along the rib.
Where it is on the gun
Top rib.
Date range
About 1900 to the 1930s.

What it tells you

What this mark authorises you to say

The lowest grade of fluid steel, and — read correctly — a dating mark. These names appear on guns made in the years when the industry was moving from Damascus and twist to steel bored from solid, and makers had every commercial reason to say so loudly on the gun. The words therefore place the gun in and after that transition, and mark it as a fluid-steel gun rather than a forge-welded one.

What it does not tell you

What this mark does NOT say

This is the most misread marking on any old shotgun. "Nitro Steel" is not a certification and it does not mean the barrel has been nitro proved. It is an advertisement for the material, and one source puts the consequence bluntly: read carelessly, these names tell people their hundred-year-old barrels are certified safe, which is not what they say at all. The proof mark, not the rib, is the safety evidence.

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 barrel steel markings

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.