Typically the best ammo for your Windicator is what shoots best in it.There are many different brands and weight of ammo available for you to try.I find that most every firearm likes one or two loads the best.It will be up to you to find out.If you do reload centerfire ammo then it is really enjoyable to try different weight bullets and powder combinations to bring out the best of your firearm in terms of accuracy and velocity.
Slugs! If its rifled it is a deer hunting barrel.
It depends on what you are using it for and which one groups best.
You need to provide the choke of the barrel and the type of game or sport you intend to use it for
Assuming you mean the Remington 870 shotgun, with a scope- is your barrel rifled? If so, sabot slugs are generally the most accurate. If smoothbore, then rifled slugs will be most accurate.
Standard velocity 158 gr semi-wadcutter. The small light 38s do not do well with +P ammo, and a 2 inch barrel does not work well with most JHP rounds (too slow to expand)
There are varying opinions on what ammo is the "best." Generally speaking, the best ammo to use is whichever ammo is the most reliable in your particular gun.
Federal premium ammo
If your barrel is marked .300 Savage then you can shoot .300 Savage ammunition by any manufacturer. I do not know of a "300 Savage Winchester Magnum".
With no more than that to go on, the best I can give you is a range of 300-3000
The ammuntion it is chamberd for.
Idaho potatoes
I have had good success with Federal rifle ammo.