I need a flip up rear, I had a arms40 and it did not move far enough to left to bedead on, I'm a lefty and usually do not have a problem with BM zeroed battle sights and do not have to move them much, since i had to on the arms40 i thought the m4 was overtorqued,sent to BM and they say nothing wrong and checked to make sure my gas block and everthing else aligned right. It still shot that way so i sold the arms 40 and i need a rear flip up. Thinking on a m600 or m300(its KAC oe something along that brand),I guess the 300 one be all i need.Just need opinoins on what everyone likes other than the arms40.

I got to looking at the prices on the knights 300 and 600 and price is out of the "?", so what about the mad rear flip up sight, think i seen them for 80.00 and higher.

I have a sneaking suspicion you're going to have the same problem with any sight you put on the rifle.  Excessive windage is almost always an indexing problem.  

Bravo2
You should have kept the #40 as they have 6 or more clicks of travel than the M16A2 rear sight, or more than any others I know of.
Suggest you try a zero'd flat top from a friend that has a #40 on it, as I guess that your bushmaster check out was flawed.
Good shootin, Jack

Agree with 3rdtk and Bradd, I think your front sight post might need to be reindexed.  just pop out the tappered pin on the gas block and reindex the front sight.  try to get that #40 back, it is by far the best feature BUIS on the market.

I already had gotten rid of it, although i liked it ,just i could not get dead on and windage was all the way to the left. BM sat on rifle for a week and did not log it in they evan had it, then they took a few days to get to it and sent it back saying nothing was wrong, it was the only BM i had that i had this problem.I still believed it was indexed wrong. I got a fulcan gas block on it with a BM flip up front sight. They evan supposedly religned to make sure my everything was right, i know my cmore was dead on before and after. They said they took it apart and checked it and nothing was wrong. I really wonder if they evan did anything too it.It was same way before i took off factory sight and forearms,figured surly gasblock and flip up sight would fix the problem but did not.it would shoot to the right and arms 40 be all the way to the left, charging handle would be over quite a bit too. The front sight would have to move to the right and it would be not aligned plain as day! I wasted time and money with BM on getting it fixed. I guess i better setup the carryhandle and try sighting it in again so i know how much its off and get a gunsmith to fix it. I will probably have to buy another arms #40,but got to get it right first.