Hello everyone.  I just wanted to run this by those who may know the LMT sight system better than me.  Okay, previously I had my AR sighted by the IBZ 50 yd zero method.  I removed my removable carry handle and installed a new LMT BUIS yesterday and took it to the range today without making any adjustments except zeroing the windage on the LMT.  My AR shot WAY high.  I had not moved the elevation on my front sight at all.  To tell you how high this thing shoots, I have a Colt taller front sight post and have had to adjust it to dead level with the (wings?) on either side of it on the front sight base to get this thing to shoot IBZ 50yd zero.  The post is almost sticking above the wings on the front sight base.  What would have made this shoot so high?  Is the LMT a taller rear sight than the bushmaster removable carry handle?  They look to be the same height.  I just dont get it.  Thanks in advance for any replies.  Also, I installed a KAC RAS II at the same time as the LMT BUIS, but it floats the barrel, and I dont see any way that could have caused the rifle to shoot so much higher at 50yds.  Thanks again for suggestions.  Almost forgot, the windage on the LMT is perfect with the rear sight set dead center and its shooting great groups at 100yds (mostly under 2 moa with a couple of three shot groups knocking at the door of 1 moa) so there is no problem there, just this weird elevation problem.  

Also, I wanted to ask what type of screw can be used to screw under the front sight post into the sight base to take any wiggle or play out of the sight post?

I had a similar problem but didn't need to back the front sight out so far.  I think it might be something to do with the FSB being too short and not made for use with a flat top.  Nut at the same time, if your carry handle was mounted on there and it worked, it should still work...  No real idea...

Spooky

[ Nut at the same time, if your carry handle was mounted on there and it worked, it should still work... No real idea.../quote]

Exactly.  I havent changed anything else but replace the carry handle with the LMT BUIS.  I cant think of what it would be except the LMT being too tall, but it doesnt really look like it is when held next to the carry handle I removed.  I dunno.....

The Lmt uppers (ie. the front sight bases)are along with their Buis is .040 higher than other brands.  Just like Colt carry handles and fsb`s being .040 higher.  Not visible by eyeballing. 040 isn`t much,  just enough to frustrate you trying to zero your rifle.  Go with the .040 taller sight post and you should be good to go.

mikeinck, I have the .040 taller front sight post on the rifle, and it is still backed Way out to get a IBZ zero.  The top of the post is level with the "ears" or "wings" on the front sight base.  I cant figure out why the LMT required the front sight base to have to be adjusted so much higher.  I am wondering if something is really out of whack, but cant think of what to blame for it.

JSIG,  I don`t know what to tell ya on that one, since you already have a taller sight post, except maybe try the rear sight aperture that RB precision is selling that has the aperture drilled .040 lower. I would imagine the combination would have to work, right????

I have the EXACT same set up as you JSIG and I have the same issue.  Sucks cause I bought a national match front sight post thinking it'd work fine - it didn't.  I have a 0.40 taller sight in there now and it works just fine.

Quoted: JSIG,  I don`t know what to tell ya on that one, since you already have a taller sight post, except maybe try the rear sight aperture that RB precision is selling that has the aperture drilled .040 lower. I would imagine the combination would have to work, right????

That sounds like it might be a good idea!  I'll have to check it out.  I was not aware RB had this, thanks.

Quoted:
I have the EXACT same set up as you JSIG and I have the same issue.  Sucks cause I bought a national match front sight post thinking it'd work fine - it didn't.  I have a 0.40 taller sight in there now and it works just fine.

[/quote
Yeah, it does suck!  Now that you have the .040 taller front post installed, did you have to back the post out until it is level with the ears of the FSB on each side?  I did, and I have the .040 taller post.  I hate having to have the post backed out so far and so tall it is level with the ears.  Now I have to figure out a way to take the play out of it.  

Quoted: JSIG,  I don`t know what to tell ya on that one, since you already have a taller sight post, except maybe try the rear sight aperture that RB precision is selling that has the aperture drilled .040 lower. I would imagine the combination would have to work, right????

I was not able to find the .040 shorter rear sight aperture on the RB precision sight.  I guess I'll call them.

I'm not too worried about it.  I nail my targets every time with no hesitation.  When I look through the rear aperature I see the post not the ears.