Gordon,
I'll respond to your PM here, to throw the info out for everyone.
The question was; whether or not the munitions could be destroyed in a manner to save the adapters.
These adapters were used in different sizes on all US CW filled projos from 75mm to 240mm. This included smoke fills such as WP and FM/FS.
As the US never used the CW filled projectiles in anger, there are only a few of them found out and about in the field today, mostly with smoke fills.
Both the chemical and smoke fills smoke can be pretty corrosive however, so there is normally not much left after 50+ years in the field.
By treaty, all chemical weapons, including those from WWI and WWII, must be declared, verified and destroyed in a specific manner. This is the Chemical Weapons Convention (CWC), which is monitored and enforced by the OPCW, where I and a few other BOCN personnel are employed.
In regard to field recoveries, how they are destroyed depends on the country involved. The CWC prohibits open detonation or burning, though allowances are made for certain extreme circumstances (not the recovery of collectable fuze adapters). Most countries that recover on a regular basis now use some sort of detonation chamber, to eliminate the need to disassemble the munition and reduce the hazard to personnel. Additives to the explosive can prolong the heat phase of the detonation, furthering the destruction of the chemical agent. The off-gases are then run through a furnace and scrubbers to decontaminate them. Typically, detonation chambers leave nothing other than small fragments of a munition the size of a 75mm.
In one country, however, a detonation furnace, or static kiln is used instead of a detonation chamber (also referred to as a hot detonation chamber vs a cold detonation chamber). This is a large vessel heated to 500 degrees C. Items pass through airlocks and drop into the chamber, where they either burn out or detonate, depending on the explosive and other factors. They are then kept in the chamber for at least 12 hours. Once the chamber is full the scrap is dumped, shaken and vacuumed to remove contaminants (arsenic) and turned over to the smelter. Often this leaves bodies in much better condition, though the metal softens and one good detonation during that time deforms everything else nearby in the chamber. This site does not see any munitions with these adapters though, plus they have pretty tight regulations in regard to their scrap going directly to the smelter.
The end result is that these can be very difficult projectiles to find adapters for. Of the CW projectiles I have seen about 75% need one, including my 4.7-inch and 155mm.