In II Samuel 24:13 God told David that he could choose 7 years of famine but in I Chronicles he could choose three years. Is this a contradiction?
In the case of 1 Chronicles 21:12 the manuscripts are unanimous that the proposed time of discipline was three years. In the case of 2 Samuel 24:13, the Septuagint has three years, but the majority of Hebrew texts have seven years. It is hard to be sure what the original of 2 Samuel 24:13 was. The fact is that in the copying of manuscripts, the copyist can make errors. The original text of the Old and New Testaments was without error and fully inspired. However, the copiers of the manuscripts were not inspired. They made errors of copying which is proved by the variations between the different ancient texts. The fact is that the copying of numbers is more problematic than letters because a misspelling is obvious, whereas a different number is not obvious. For example, if I saw the word dinofaur in a text about ancient lizards, I would know that a copying error was made and that the f should be replaced by a s. On the other hand, if someone said that Billy Bob Smith lived at 8550 Lincoln street, I would not be able to tell if there was an error and the correct address was 8552 Lincoln street. The most common and likely copying error from ancient manuscripts involves numbers, which would explain the apparent contradiction between these two passages.
The simple answer is no, this is not proof of a contradiction. It is evidence that there was a copyist error, more likely in 2 Samuel (7 years) than in 1 Chron (3 years). The Bible deserves the benefit of the doubt, given all the evidence for the inspiration of the scripture. However, bottom line, we cannot PROVE that there was no contradiction in the original, but neither can the skeptics of biblical inerrancy prove that there was an error in the original. This is an apparent contradiction but if we consider the history of the text, it is an apparent one, but very likely the original of 2 Samuel 24:13 and 1 Chron 21:12 did not contradict and that a copying error occurred.