I have to jump in here and say there isn't really a shortage of ammo. We've got plenty and its usually prepositioned based on the forcasts that users gave us.
From what I have seen is there is one main problem with perceived ammo shortfalls. Lack of communication. If the user does not tell us that they need ammo until the day before they want to draw it, well if it is in stock in at the base where they are using it they will probably get it, if it has to be ordered in, maybe they will, probably not though. In Gagetown we regularly get orders for items that were not reflected on the forcast we got in Feb for the upcoming year that we ordered our stock against. Ammo sections do not control allocations and therefore don't get info'd on changes to allocations, normally we get a draft of the proposed allocation in the Feb-Apr time frame and order against that. So if you unit is gifted with an extra 20000 rounds of sniper ammo but don't bother telling the ammo compound you need it until two days before the range, well I hope we have in stock (very real, very recent example, no shortage there, just poor planning).
The other point, and one that is getting better in recent years, is units wasting their allocation, especially of SAA. We regularly get back loose mixed rounds, and unless the unit is willing to repack it, it'll be considered expended unless you are authorized to keep it loose in your own ammo lockup, and for visiting units thats not an option. I have seen units show up, draw several cases of ammo, only have a few pers show up to shoot, and return thousands of rounds loose. Tell them, "You wont get credit for this unless you repack it", reply "Thats fine, we've got to get home." And I wont even get into amnesty boxes, it is obvious to me that either, A. Range staff are not doing declarations, B. Pers are lying on their declarations and then getting cold feet, or C. Pers find a good chunk of ammo in vehicle/kit/lunchbox after delcaration, hand over to CoC who then throw it into amnesty box because its almost time to go home or the QM staff aren't around to take it.
Yes, ammo does have 5 year or so purchase cycle but the ammounts we buy are driven by Ops not Log. They tell us how much they will need and we buy it. If it changes, well that can be dealt with, but you need to pass on the info in a timely manner. We no longer have Crown ordnance factories, we have to deal with private companies that are both profit driven and probably dealing with other contracts.
The ammo is in the system, the G4 side of things are only to happy to push it out the door to the users and get nothing but salvage back. I hate to play a branch/cap badge blame game, but G4 generally don't make decisions, they execute plans developed by Ops/Trg. However until Ops/Trg down to the lowest level can tell us what is needed when and where in a timely manner problems will exist.