When 13 year old Bob decide to handover certain family artifacts and heirlooms of over 300 years to the British National Museum, an ancient war resumes and to stop the war, Bob has to go into the past to right the wrongs made by his ancestors.

I hear you loud and clear JanCabal... Perception is the main challenge here. Writing is just like art, people can read different meanings into a piece of work and people can give different "expert" opinions based on varying p.o.v.

As sharkeatingman once replied to me, writing loglines is an excellent tool to uncover potential weaknesses of the script in the entire beginning of the process. And I have to agree. You can spend one week shaping up your logline to save months writing the script which you won't sell - because you will fail to present it to someone who matter with an intriguing logline. It helps you to identify basics - protagonist, antagonist, inciting incident, goals and whats a at stake.

"He have to correct mistakes" is very unclear whats going on - It can be minor thing, or it can be chain of important events and smart manipulations. Trait of a hero may give us a clue how he will do that. Cunningt, genius, courageous ...

Lines about history if its 300 or 500 does not matter in the logline. Same goes for the name of protagonist or which museum it is. You can save some words by cutting that out.

Hope it helps!

Thanks nicholasandrewhalls...

Is it just me or it's easier to write a script than write a logline? :)

I don't want to get sucked into a situation whereby progress is dependent on a logline.

"A young boys quest to close a dark chapter of his lineage unwittingly opens up a whole new world of trouble for him."

OR

"A young boy's quest to close a dark chapter of his lineage unwittingly rekindles an age long war which he struggles to stop."

As an aside, I came across this website which you might find useful -

http://www.twoadverbs.com/logline.pdf

First off, what is Bob's character flaw? (I'd avoid using his name in the logline as well).
The meat and potatoes of the film appears to be Bob going back in time 300 years to ... do what? This unclear. Righting wrongs of his ancestors is a little too vague.
With that in mind, you don't need to spend quite as much time on the set up, I think. Something more along the lines of "When some ancient family heirlooms revive the ghosts of his ancestors locked in a bloody battle ...". Or something like that, only better.
As a note to one of your comments, you say that Bob needs to stop the way to save his own health. Those stakes are just way too low. Maybe save his life? Save the life of everyone in his family? Make them higher for sure.

Thanks mmckean... the revision was just an attempt to reduce the length of the Logline. Bob is a descendant of a man who was a major player during the trans-atlantic slave trade. The artifacts were some personal belongings of some of the they took as slaves. Its the spirit of the slave masters and that of the slaves that resumes fighting... Bob believes he has to stop the war to save his own health

I'm assuming your comment is a revision of your log line, so Ill work off that one. First, the logline brings up a lot of unanswered questions. Like what these treasures are and what ancient war and what wrongs bob's ancestors committed. A little mystery in a log line is essential, in my opinion, but there is a little too much here and it makes the reader unsure whehter or not this story would appeal. Try really thinking about the main idea behind your story and work from there. Is it the war? Is it Bob and his ancestors? Is it the treasures? What do you want to emphasize and what do you want to leave mysterious? I hope this helps. Keep writing.

When Bob hands over family treasures? to the Museum, an ancient war resumes. To stop the war, Bob has to right wrongs of his ancestors.