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Mk1 grenade detonating fuze :

The US grenade fuze with the "mousetrap" mechanism was first used in WW1 on the Defensive grenade Mk1. A cocked striker was kept in place by the lever which in turn was kept in place by the fuze cover.
The fuze body was made of lead and held a 5 seconds delay. It was fitted with a No.6 fulminate detonator.


unidentified Mk1 fuze

The fuze shown on the right seems to be a bit different from the normal ww1 fuze.
Does anyone have any info about it?
Let me know.

Mk II detonating fuze :

Around 1918, the old style Mk1 fuze was altered to ease both production and use. The old fuzes in stock were changed by grinding off the lug. Instead of the rotating lever, a new short lever was fitted, see right photo.
When all old type fuzes were used up, the fuze manufacturing was continued in this form. This production has no grinding-marks.

Like the Mk1 fuze, it was fitted with a No.6 fulminate detonator. Lead fuze body.

Photos below show an altered fuze on the left, and a factory produced fuze on the right.
Photos right and below © Dr. Ruby.

Like above, but with rare dirt cover:

1939? M10 variation :

The photo on the right and the two below show what appears to be one of the earliest types of M10.
The dirt cover differs from the type shown above.

Photos © Bradley.

M6 detonating fuze :

The following types exist in this serie:
M6, M6A2, M6A3, M6A4, M6A4C, M6A4D.
"C" is a Curved lever (
Mk2A1), "D" is a straight lever (M15/M34)
The detonator is waterproofed with RED sealing paint.
When the fuze was fitted onto a grenade, they were waterproofed with a tar-substance.

Detonating type with a delay of 4-5 seconds. Alloy body.
Used with Mk2A1, Mk3A1, M15 and M34.

M6A4C and M6A2

M6 left, M10right :

when half black, the lever is re-used :

M10 igniting fuze :

The fuze body and lever are similar in appearance as the M6 detonating fuze.
The tube on which the igniter is crimped is slightly longer then on the M6(see above).
This igniting fuze has a delay of 4-5 seconds, and was only to be used with grenades filled with EC blankfire powder or Blackpowder. Alloy cast body. (fully aluminium are known too and might be end- or postwar).
The blackpowder-igniter is waterproofed with GREEN sealer.


M10 : 4 - 5 seconds delay
M10A1: declared unsafe
M10A2: 4.3-5.5 seconds delay.
M10A3: 4.0-4.8 seconds delay.

M10series fuzes were used on MkII, Mk2A1, MkIIpractice and M30practice.

WW2 production line :