US made 40x311R Bofors 40L/60 clips

Can anybody explain why there are so mann different designs and why some have typical “M” designations while some have naval “MK” marks.
Is there any good information source for all the variations?

The highest “MK” number I have seen recently was MK7. So does it mean there are at least 7 naval clips + their Modifications?
And what about the “M” types then?


There is at least a MK 3 and a MK 5 MOD. 1 version as well and based on construction differences between these two, I would guess there was an evolution towards a much simplified device.

I don’t have any “M” clips but I think while the “MK” are Navy the "M"s would be Army, etc.

Would be interesting to see the series of US clips as compared to Bofors’ original design.


Dave, right now I can’t even tell how the original Bofors clip looked like. I assume it was the cast aluminum design as we know them from the UK and Hungary (and also copied by others) but I have no info as for the “original”.

The US “M” type I know of was the M3. The US types I have seen looked all like simplified versions made of steel sheet and the MK7 made of zamak (cast zinc alloy).
If the 40mm is still in use in the AC-130 gunships I would like to know what clips they are using today.

Maybe somebody can shed more ligth on this?

Here’s a picture of gunnery practice aboard a US aircraft-carrier, I believe quite early in the war. The clips, in their ‘ready-use’ holders are easily seen, as is quite a bit of expended ammunition.

I wonder how many turned ankles there were, reaching for a new clip with all that stuff underfoot.


Peter, it is still impossible to ID the clips in the images.

The spent cases went to the front while full clips were coming from the back.

I’ve looked high and low for drawings that show the clips and how they work, but without success. Even the manuals seem to assume that the clips just exist with no other information necessary.

These things are rather beyond my collecting interest anyway, they’re clips and they hold cartridges, but if I ever allowed myself to collect them of this size I’d soon be living in my shed. I’ve handled lots of them but I’ve never even been tempted to buy one and take it home … phew!

Here’s another picture, again only with limited detail but I hope someone, somewhere has more detailed information.


Here are a couple images of the U.S. MK 3 clip with one case installed and a U.S. MK 5 Mod.1 in roughly the same orientation to show the differences in construction.


Dave, thanks a lot! That MK3 should be an M3 no?

The MK5 I have not seen before, again it shows the variety of all of these clips.

Anybody out there who could show the most recent US clips?

I did a quick image search in the web. Found these: … bnail1.jpg

Here we can see at least 3 different clips: … _small.jpg

Here another type: … 47-013.jpg

Not to forget an old thread we had here before:
[40MM clips)


Nice pics and thanks for the link to the old Forum.

The items I showed above are marked as follows:

40 MM. CLIP MK.3
INSPT. A.L. [US Anchor]

NOs. 90903
DR. NO. 328801

INSPECTOR R.V. [Anchor] [1945 in stylized “M” in circle]


Other than the fact that I’m not as smart as Peter when it comes to collecting such larger things, I don’t have any other specific info on these clips. I take it the one marked “MK.3” is like an “M3”? From the pics in the thread you linked to, my “MK.3” does look different from the one shown there.


Interesting, so the M3 and the MK3 look very similar.

In both the AC-130 pictures the clip is visible but wasn’t thought important in the picture so is obscured by the shell cases. I ran the second picture through Photoshop and found that the ‘ready use’ ammunition is visible although it doesn’t make a pretty picture. From it though it might be possible to compare with other clip pictures to see what model was being used.

I can’t believe that something as vital to the operation of the gun isn’t illustrated somewhere, there must be design drawings, manuals and training protocols somewhere.


Peter, the drawings do certainly exist as it would not work without. It just depends on if the regular soldier needs to know the details (and we know the answer to that). In the supply chain it is nothing else but a 4-round charger clip which is being handled, loaded and used in the same way and same weapon. Putting details into a manual would be superfluous as there is already other important stuff to be known which is impossible to remember for so many guys (knowing all the incidents and accidents and just stupid things related to all this)…