Here is a picture of the two halves apart. You can see that the entire lower slimline tube is present - and much of it extends from the 223 case head. Even so, the transmission isn't inserted as deep as usual. The press-fit part is just barely all in. The upper barrel is longer than a slimline tube by the same amount that the lower tube sticks out. The tube is glued flush at the nib end, leaving an unsupported section of blank that slips over the lower tube. This is very similar to how I make 308 Winchester pens, except that more tube and more transmission are exposed.
I haven't given much thought to listing this cartridge for sale on my website, but I certainly could make it by special order. I've done custom calibers several times before.
I hope this picture shows the colors a little better. The bullet is copper-jacketed; the case is brass, the blank is camo dymondwood, and the kit is 24k gold.
I'll try to post a pic with other pens present (to give a sense of scale) soon.
Regards,
Eric