I used to "berm mine" and it is a mixed experience - on one hand you get free lead, then you actually make money when you sell the copper jackets at the recycling yard ($1.70/lb last time I did it), on the other hand it is hard work, then waiting for the things to dry, then messing with melting them - if you shoot a little it is OK, but unless you get them from an indoor range it is too much work for me.
If the bullets are from an outdoor range, make sure they are dry before melting them - 2-3 days spread under the sun on the driveway will dry them very well.
Make sure you try to separate the TMJ bullets and intact copper plated bullets - as noted above, they can and will squirt molten lead when the pressure gets high enough.
Using a heavy lid will help in two ways - it will keep those popping rounds inside (yes, you will have them no matter how long you dry them, some moisture will remain trapped inside until the rest of lead is melted) and also will keep the heat inside - copper is a very good heat conductor and it is much harder to melt jacketed bullets that lead ones.
Wait until you don't hear any more popping and use a long stick to open the lid and see if they are melted. The copper jackets will float on top of the lead. Using a straining spoon to shake the jackets will release most of the lead still trapped inside them. It is a slow process, in the end you will end up with a bunch of copper jackets, some dirt and some lead.
The lead will have different hardness, if cast bullets are allowed at the range it can be anything. In my experience it was about BHN 9-10.
If only FMJ bullets are allowed, it will be close to pure.