WeaponType

The type of weapon and the damage it does.:

1 = Piercing

2 = Bludgeoning

3 = Slashing

4 = Slashing and Piercing

WeaponSize

The size of the weapon. These numbers correspond to the rows in CreatureSize.2da.

RangedWeapon

Index to the row in Baseitems.2da specifying the type of ammunition used by a ranged weapon. Projectile weapons point to either row 20, 25, or 27. Thrown weapons point to themselves (i.e. they are their own ammunition).

Note: it does not appear to be possible to create a new ranged weapon, although it is possible to replace an existing one with a new ranged weapon. 

PrefAttackDist

The preferred distance for attacking with this item. Only relevant for weapons. Used to determine how far away the character wielding the weapon can be from the target and considered to be in melee range.

MinRange

The minimum number of models of this type. The actual value to put in here is the range you want x 10. 

For Multi-Part Items (Weapons): A value of 10 here indicates that your model numbering starts at 011, incrementing by one to 019, before indexing by 10 (e.g. 019 >> 021-029 >> 031 etc. 

MaxRange

The maximum allowed number of weapon models of this type. The actual value to put in here is the range you want x 10. The maximum possible value is 255.

For Multi-Part Items (Weapons):  The MaxRange should be set no higher than 250, as the hard-limit is 255, eliminating models 256-259. When making custom content note that you will not need models 010, 020, 030, etc. Nor am I certain the engine will render such models if they do exist.

For Single-Part Item: The full range of numbers is available starting at the MinRange value and ending at the MaxRange value.