I have a smith&wesson m&p-15 with a gas block on it. I have some magpul front sights, and it says on the box, "due to excessive heat, do not mount on rails on gas block". My question is, if i mount the sight just behind the gas block on the hand gaurds, will this affect the accuracy of my sights? or do i just need to bzo the sights from there? Also, if i want to remove the gas block, what part do i need to get to replace it with? please help. Thanks.