- I originally posted most of this to 'home guard thread' reposted here since I think it's relevant to 'reloading' or more correctly manufacturing 'heavy weapon ammo.'

- I think most decent colleges, and certainly all agricultural or mining schools, chemistry departments have the foundation knowledge to make base components for munitions. Black powder is fairly easy, smokeless powder and explosive components more challenging. Primary explosives for primers and initiators more challenging still. The know how to make explosives would be found in most chemistry departments, it is likely it would have become more readily available as the nation moved to war footing.

"For a militia or home-guard unit, a decent bomb squad would be 'fairly capable of providing the knowledge to design fuses and make "home made explosives." Combined with machine shop capabilities this could be very powerful/useful to the Militia (or a marauder band.)

Land mines and IEDs are fairly simple to improvise. Grenades as well, the first were simply metal balls filled with blackpowder and lit by a burning fuse. I would not think rifle grenades would be that hard to manufacture.

Fuses for explosive rounds are harder, but not impossible. Different types of shells have to have different types of fuses. exploding rockets, mortars and then cannon shells might need different fuses to function based on the increasingly high velocities and forces involved in firing.

"Barrage Rockets would not be hard to improvise, but 'accurate rockets would be more challenging. Recoilless rifles have been improvised by the IRA, but they require a quality steel and knowledge to make the breach. I could see a "bazooka" making a come back, perhaps firing either HE or shaped charge rounds.

Munitions for AFVs. The easiest round to make for any gun would likely be a 'cannister or 'shotgun' round. It could be as simple as a black powder charge behind the appropriate weight of ball bearings, lead shot, marbles, rocks..., initiated by an electrical current passing through a glow plug.

Solid shot would require machining but should not be hard for a machinist to make, with tools common in high schools.

High explosive shells would be fairly easy to make. Reliable fuses for them more difficult.

Electrical ignition might be easier and more reliable, but then your rounds are likely going to have to have a battery, and thus a 'shelf life.'

Small Arms:
- Reloading of revolvers, shotguns and some rifles (30-30 for example) with black powder is very doable. Most automatic/semi auto firearms will not reliably work with black powder.

- Reloading of modern rounds, if smokeless powder is available, is easy, and thousands of American hobbyist do it.

- Making smokeless powders and primers is more challenging. I'd expect that getting plants into production would be a major drive for organized groups. Once built they would produce a very valuable trading item. The technology is not that difficult, but it does assume a level of security and trade.

Forgot that the WWII to Vietnam mortar rounds used a modified shotgun shell for ignition. The WWII 60MM used a paper 20 gauge. I know a cartridge collector with fun items in his collection. Some autocannon use electric primers, and won't work in similar guns, 20MM's are like that.

The British L118 Light Gun used electrical ignition via a piezo-electrical device, no battery needed.

It used brass cased semi-fixed ammunition IIRC.

for larger guns if you don't have a large amount of metal you can make sobot rounds. it's easier than it sounds since the material for the sabot only has to work once, unless your sending people out to collect the spent sabots after an engagement.

sabot ammo can also be made for a wide array of calibers all the way down to .30 M1 carbine.