I always save chicken backs, wing tips, hearts and gizzards,bones after boning and scraps from cleaning BSCB. The bags add up fast. Since my freezer runneth over I pulled out a 5lb bag of chicken scraps. Using my 6 qt pressure cooker I made 2 batches each combining chicken with an onion, celery, carrots and 2 qts of water. I cooked at pressure for 40 min then did a natural release. The bones were soft and crumbled to the touch. The stock was remarkably clear and all the scum was stuck to the bottom of the pressure cooker. This was a shocker. I had expected it to be all over the lid or suspended in the stock. I had to really scrub this out between batches. My last attempt at stock with 10lbs of scraps and bones and cooked for 8 hours did not produce the concentrated flavors I got with the pressure cooker.
The stock was light brown in color and gelled nicely when cooled. This will be my preferred method of making stock. The only problem is volume in the 6 qt. PC but can be made up in speed and multiple batches. This is also a nice way to make stock on the fly for immediate use.