I would contact your airline.
As E said, in RSA the ammunition case will be flying separate. So, if it gets banged around will the soft case protect the ammunition. It is considered a hazardous good by the airlines. Do you want to test the theory?
From one airline:
"Ammunition must be packed in a separate, secure and strong container made of wood or metal. The original fibreboard carton can also be used but it recommended that the carton be placed in a secondary package such as a resealable plastic container. To avoid shock movement, the properly packaged ammunition must then be placed inside a suitcase and cushioned with clothing."
Still does not lay out what "secure" is.
Transport Canada:
Boxed cartridges: With the approval of the airline(s), passengers may bring securely boxed cartridges (1.4S, UN0012 or UN0014 only) as checked baggage only, in quantities not exceeding 5 kg per person for that person's own use, excluding ammunition with explosive or incendiary projectiles. Allowances for more than one per person must not be combined into packages.
IATA airline scheduled flight permissions and approvals
The phrase Div. 1.4S, UN 0012 or UN 0014 denotes the categories of ammunition that the IATA permits to be carried on passenger flights. In simple terms, each passenger may carry up to 5 kg of weapons cartridges of less than 19.1 mm caliber being either blanks or with solid projectile(s), in their checked baggage. The IATA published the minimum requirement for an airline for the carriage of dangerous goods in a table, where ammunition of the following nature can only be carried subject to the following permissions and approvals:
Ammunition (cartridges for weapons), securely packaged (in Div. 1.4S, UN 0012 or UN 0014 only), in quantities not exceeding 5 kg (11 lb) gross weight per person for that person's own use, excluding ammunition with explosive or incendiary projectiles. Allowances for more than one passenger must not be combined into one or more packages.
Permitted in carry on baggage: NO
Permitted in or as checked baggage: YES
Permitted on one's person: NO
The approval of the operator(s) is required: YES
The pilot in command must be informed of the location: NO
Division 1.4S
Division 1.4 refers to the specific nature of the ammunition, and the suffix "S" refers to the packing, as follows [2]
Articles and substances that present no significant hazard. This division comprises articles and substances, which present only a small hazard in the event of ignition or initiation during transport. The effects are largely confined to the package and no projection of fragments of appreciable size or range is to be expected. An external fire must not cause virtually instantaneous explosion of almost the entire contents of the package.
Note: Articles and substances in this division are placed in Compatibility Group S when they are so packed or designed that any hazardous effects arising from accidental functioning are confined within the package unless the package has been degraded by fire, in which case all blast or projection effects are limited to the extent that they do not significantly hinder fire-fighting or other emergency response efforts in the immediate vicinity of the package.
United Nations UN 0012
UN 0012 defines the category 'Cartridges for weapons, inert projectile or Cartridges, small arms', being "Ammunition consisting of a cartridge case fitted with a centre or rimfire primer and containing both a propelling charge and solid projectile(s). They are designed to be fired in weapons of calibre not larger than 19.1 mm. Shotgun cartridges of any calibre are included in this definition."
