20x102 experimental aluminum case

GMI-1-4 53 20MM - T61E1

Edit: found more info on @orpheus72 's site

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Jess, is your’s inerted, a dummy or a TP?

I believe a TP… has no markings at all that I can see and is not inerted.

I have the T61E1 Projectile listed as:

Projectile, Experimental, 20mm (made from a shortened M99 projectile)

you can find one of the (early) reworked M99’s here:

I guess they should be considred as ball/TP (as the M99 was Ball)

As for my complete round, it’s emptied by drilling a small hole in the case

Here are a couple of draw pieces and an electric primed fired case.
The upper has some light turning on the base and case. The middle case MAY I’m not sure need another draw at the neck / mouth, as it seems a little thick,


Those are very nice!


The fired one has an inner bulge / step at the base of the neck & looks to be a bullet seating stop, as it seems to be placed exactly right at that point. The case mouth / rotating band and the crimping knurled groove all match up with various bullets.

Loaded example is pretty neat too,