what do you think the proper slug is for a 20 gauge remington 870 pump express mag? and for a 12 gauge remington pump express mag
There are a lot of choices out there and one could spend LOTS of money searching for the best for a particular gun. There are two types I've used that seem to be a great combination of performance/cost. Remington makes a slug called the Buck Hammer that will work well in a smoothbore, and also in a SG with rifled tube or barrel. Not the absolute least expensive, but excellent performance, power and penetration.
The other slug I'd recommend is the Brenneke Foster type KO version . It also is recommended for both smoothbores and rifled tubes and it is priced very competitively. Brenneke is the original make of "rifled" slugs and has been making and modifying them for over 100 yrs. They are excellent slugs.
Do not waste any money on the more costly sabot-type slugs as they are primarily designed for rifled barrels and would not give superior performance from a smoothbore barrel.
When calling coyotes, more often than not they will circle on a target they are
coming into and approach from the downwind side. Presumably they do this in
order to align what they smell, with what they are hearing.
This means that you should always have your downwind side camouflaged and have
an open shooting lane. If the area is heavily covered the coyote could come in
take a look and be gone, with you none the wiser.