CAUTION: The following post includes procedural information beyond or not covered by currently published handloading technique. USE AT YOUR OWN RISK. Neither the writer, The Firing Line, nor the staff of TFL assume any liability for any damage or injury resulting from use of this information.
May be just stuck from compressed load packing, but I've also pulled down old surplus with grains stuck together because it was a double-base powder whose nitrocellulose had started to break down and the oily nitroglycerine had come out and jammed it up. Such powder may or may not have deteriorated deterrent coatings, too. If so, then the burn rate can be higher than it originally was, also posing a danger.
The fact it was stored properly is not a guarantee it is good. There have been several instances of powder recalled by its manufacturer because it began to deteriorate prematurely. In particular, one lot of IMR4350, a powder sometimes used in your chambering, and a lot of IMR4007 (though that was too recent to be of likely concern in 15 year old loads). The problematic 4350 lot, though, was in the early 2000's, IIRC, which is right in your time frame.
In your shoes, I would not try to fire the loads. Old powder makes good lawn fertilizer, though, so I would figure out how to remove it. For myself, I would probably wrap a strip of rubber around each case to allow me to grasp it with pliers. Wearing appropriate eye, ear, and hand protection, I would then submerge it in a bucket of water, holding on with the pliers, and use a 1/4 inch by 1 foot long electrician's drill bit (these were available at Lowe's last time I looked) on a variable speed hand drill to carefully drill the powder loose down close to the flash hole. This should remove enough of the bind for a dental pick, O-ring pick, or even bent coat hanger wire to remove the rest. Should inadvertent ignition occur, the water offers considerable protection, but I would have a full face shield on anyway.
Primers can be hard to kill. They may or may not survive the submersion. But if you want to reload the brass with your favorite load and you don't know which primer he used, I would consider knocking them out with a Lee manual decapper, also under water, or else decap on a press very slowly. Again, wear appropriate protection doing that.
If that is all too much trouble relative to the value of the cases to you, I would pull the rest of the bullets to reuse, but ask the local fire department to dispose of the primers, cases and powder, and buy new cases with some of the potential savings in medical bills from not having fired them.
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