That is true (Though lack of a strength bonus might become a pain against the tougher monsters [But perhaps they are meant to be painful?
). And of course Holy, Silver, whatever bullets are to be encouraged but it remains that in 3.5 DR is overcome in many cases by damage type (i.e. Slashing, Piercing, etc.), that Ballistic damage is not included in 3.5, but that if it were (or, had Modern used similar rules for DR) there would have been creatures with DR X/Ballistic.
If I want to implement this into a game my options seem to be:
1) Create new creatures with DR X/Ballistic
2) Change the DR of some creatures to be X/Ballistic
2a) Alternatively, add this as an 'or' entry to DR of some creatures.
3) Rule that Ballistic damage overcomes some other type(s) of DR
Currently I lean towards #3, with Ballistic counting as Bludgeoning & Piercing
Arguments against: This might make firearms far too desirable, especially if it is not difficult to acquire special materials for ammunition (cold iron bullets?), with almost everything but slashing being covered by one weapon.
So, I don't know. Maybe I should just keep going with the simulation and take note of how the alternatives would have affected things. Although again, the only enemies in use with DR overcome by damage type want slashing, so whatever effect I see will be understated.
Seems I am posting a number of threads with the resolution 'sort it out on my own' (Though, responses/advice still welcome!). Sorry about that folks. Seems to help the problem to type it out like this, at least.