When Otis, Baby and Spaulding are riding in the car toward the road block, after the incident with officer Wydell, there is blood all over the car, except not on the lower part by baby's leg where she was shot previously.
When storming the Firefly house, Sheriff Wydell is loading a Remington 1100 shotgun (a semiautomatic), but when he is shown from behind firing upon the house he is clearly using a Remington 870 (a pump action shotgun).
The Chevrolet K5 Blazer that Wydell Drives is an '86 Model, but according to surroundings and other tell tale signs, the movie takes place in 1978. This can be proven when Officer Ray Mentions that Groucho Marx and Elvis Presley "died last year".
Two of the officers storming the house at the beginning of the movie are firing M-16's, which fire a .223. The armor the Fireflies wore would likely not have provided sufficient protection at the ranges the officers fired from.
The license plate from the vehicle that is stolen from the maid by Baby and Otis is an all numbers license plate. This type of license plate is only used by government vehicles. Civilian vehicles would have both numbers and letters.