I'm only making a guess at what an "R" rating is (similar to our "15" rating I suppose) and I don't think I like the sound of anything LBT getting an "R". Still, I've never read any, so I won't make a final judgment.
To explain the ratings:
On FF.net the "R" rating is also known as "M" and it means: "not suitable for under 16".
The true "R" rating is usually used for movies and means: "not suitable for under 17".
On FF.net the "PG-13" rating is also known as "T" and it means: "not suitable for under 13".
The K+ rating of FF.net is about equivalent to a PG rating.
In the British rating system:
British:------------American:
U = G
PG = PG
12 = PG-13
15 = R
18 = NC-17
I got the rough patterning from
http://www.bbfc.co.uk -----------------------------------------------------------------------------------------------
*On a funny side note*: Malte's post:
dinosaurs equipped with human weaponry
That conjured a bizarre image of Ducky wielding a shotgun (not that she'd ever do that. I don't think she could even lift it, let alone fire it in her current size!

)
Remember, it is possible to make a good "LBT war fan fic" (Fan fiction where a dinosaur war is implied or actually occurs. I can cite 3 good ones:
Land Before Time: War of the Worlds (By Falcon88),
Land Before Time: Twilight Valley (By Serris/Jakayrta) and
Innocents Lost (By Tony Dimera). The last one implies war, the first 2 actually involve war.)
Even if you are writing a "LBT war fan fic", I did set some guidelines:
1.) Weapons are permissible but they must be primitive (basically only what would be found in nature: sticks, stones, poisonous plants, fire etc. <fire does appear in
War of the Worlds and will appear in
Twilight Valley for peaceful and military use.> I did make an exception for blowguns as they are simply hollow reeds).
2.) Military lingo is acceptable AS LONG as it is somewhat modifiable to fit in the LBT universe.
3.) No military ranks or titles.
4.) Humans and modern human weaponry are NEVER to appear in a dinosaur war.(That is not to say this can't work in LBT fan fiction
Time Gate X (By Cyberlizard)) provides a fairly good example of how it could work (there's even a scene where *Spoilers*).
But unless you age the LBT characters, sexuality DOES NOT belong in LBT.
*On a side note "links with #4" *:
An original "furry" SF/fantasy fiction I'm writing also features the "time travelling human researcher who finds that dinosaurs are sapient and capable of speech" motif that Cyberlizard's story has but the plot is totally original. The researcher in my fan fic is a civilian but he is familiar with small arms and heavier munitions like rocket launchers (might need to be if you are going into the Jurassic!). He does not have all that much military training other than familiarity with various ranged weapons .
During one of the space station chapters, Deimos (OC from my fan fiction -Deinonychus) will fight with a terrorist and he'll kill him by wresting his pistol away and shooting him in the head. Needless to say, the researcher is suprised (later revealed that Deimos learned to use firearms by imitation <he gets a brief lesson on firearms from the researcher during a little lull in the action and he learns REALLY fast>) I made Deimos a little more human-like (good problem solving skills and human-like dexterity). The Struthiomimus character will also use a weapon (a knife he takes off a terrorist the researcher shot and killed)
I aslo had somewhat inspiration from the plot of Jurassic Park IV (involves genetically modified Deinonychus as mercenaries)
*SPOILER FOR TIME GATE X*Pterano seizes Tanner's pistol and shoots Sierra through the head with it, killing him. Earlier, Yu (OC from the story-Velociraptor) decapitates a velociraptor and stabs another one with a knife, that Tanner gave him.