I just tried to pressure-can. A trial run. Prepared some green chile salsa and filled five boiled 1/2 pint jars. Tightened the rings finger tight and PC'd on a trivet in about 1" water for 15 minutes with a 10 minute natural release.
Only one jar survived.
The rest leaked real bad and when cooled the rings gave way very easily.
I could have tightened them more but stopped just past the first snugness. Maybe another 5-10 degrees?
Interestingly, the salsa turned out good- the flavors melded and it isn't too mushy. Hot fire in my belly.
Sounds like you might have had the jars too full. Leave 1 inch of headspace - no more, no less. If the ingridents boil out and get between the lid and rim they won't seal. You can snug them down a little more also. The principle is the air escapes out when boiling and then seals and creates a vaccum as it cools. If the rings are cinched down too tight the air can't escape and real tight will distort the sealing surface and keep them from sealing.
Start with hot jars and hot ingredients. Put the jars in boiling water. If you don't have an extra pot that big, fill the jars with water and sit them in a pot with at least water half way up and bring to a boil. Start with cold water inside and out to prevent cracking. If you have a big pot put the jars on their sides and boil. Start with cold again for the same reason.
Be careful of the hot jars and water. Get you one of these if you are taking this seriously. It will save your hide. It has all the handy tools you need.http://www.amazon.com/Back-Basics-286-5-Piece-Canning/dp/B0002BF1WY/ref=sr_1_1?ie=UTF8&qid=1314395947&sr=8-1
(if you use this funnel and fill till the ingriedents touch the bottom then you will have the correct headspace)
Dump the water, fill to within one inch of headspace, wipe the rims to make sure there is nothing on them, lid and ring.
After cooking, let the cooker cool down and on its own and release pressure naturally. At this point it will be at 212f (or your boiling point depending on altitude so be careful). Don't release it manually or run cold water on it. That will also cause the contents to boil over.
Take them out and leave the rings on and let them cool completely at least 12 hours
. Set them on a towel and leave a couple of inches between them. The lids will "pop" concave in 10 - 30 minutes but they haven't pulled a complete vaccum until everything is room temp. If one doesn't seal, throw away the lid, wipe the rim and re-lid using a new one and try again. If you can't do it right away, then refridgerate and eat soon.
Never reuse a lid. The rubber seal part is heat activated and it can't be reused.
Try again, we'll get you canning yet