Food, consistency, strength, and toughness...
People posting on this list may have a somewhat simplistic view of sericulture. A great reference is Principles of Sericulture by Hisago Aruga. There are several issues that are of interest. First, although silkworms can be raised on silkworm chow, those caterpillars are less likely to cocoon. They eat, grow big, and then ... die. Mr. Thompson alluded to this issue in one of the press releases. More caterpillars will cocoon if fed actual mulberry leaves. You can start the caterpillars on silkworm chow and transition them over to mulberry leaves. In any case, actual mulberry leaves are preferable to chow. Hence the purchase of 2,000 trees.
Next, breeding the silkworms is trickier than it might seem, even though they are homozygous for the spider silk genes we want them to have. Some will grow big and fat, others will be smaller. The silk they produce will be slightly different. Thus, someone has to pay attention to the worms and cocoons in order to pick out the right parents for the next generation. Here is why:
When silkworm moths leave the cocoon, they break through the thread any number of places, leaving only short pieces of silk that are not suitable for making thread. You only allow the ones you want to breed to emerge from their cocoons. The rest are killed in hot water as the cocoons are prepared for spinning into thread.
Given that silkworms are different, you have to select which ones to breed and which ones to boil. Randomly picking breeding pairs will lead your colony to produce thread that varies in consistency. I don't know if that was the problem with the first source that KBLB tried to develop, but it is a likely candidate.
One poster recently posted that silk is tougher than kevlar, even though DS is not as strong as Kevlar. This is a very important point. Spider silk will absorb far more energy than Kevlar will, meaning a bullet that will pierce Kevlar will not break through spider silk. This is because of the toughness of the fiber. (I haven't seen stress/strain curves on DS, but I believe it is tougher than Kevlar.)
That might sound like we have the ideal candidate for bullet-resistant vests. Yet there is a tradeoff. The toughness comes from the elasticity of spider silk: It stretches. Kevlar stretches very little and then breaks. DS will stretch a great deal more and, in the process, absorb more energy.
The implication for shot packs is simple: the bullet will crater further, potentially causing blunt-force trauma that could be lethal. This is one of those 'all other things being equal' statements. But they aren't. Kevlar is not tough enough to stop rifle bullets, which is why a higher-grade vest will have a heavy ceramic plate that is tougher than Kevlar. Creating a thicker and denser DS shot pack might improve on their resistance to rifle rounds without the weight of ceramic plates. A big win.
Layering both Kevlar and DS might be another answer -- I certainly don't have the knowledge to model the physics of these blended fabrics.
A third possibility is to use a 3-D weaving process. Fabric is knitted or woven in sheets. But some 3-D weaving technologies can produce a thicker fabric more like a pad. I believe the stretch might be propagated through a larger volume of the shot pack and thus produce a shallower-but-broader impression.
Finally, sericulture is a very labor-intensive process. One reason that Mr. Thompson wants to go to Vietnam is simply the cheap labor costs there compared to the US. Silkworms are delicate and have to be protected from different diseases, fed carefully, selectively bred, and spinning thread from cocoons takes a lot of work.
Expect industrial strength dilution in the coming months!
