I want to use a flipup rear sight on a BM flat-top with the standard front sight tower.  It looks like my choices are the ARMS 40 or the new Bushmaster B.M.A.S  flipup sight.  The ARMS seems well regarded, how about the Bushmaster sight?  Will I need the .040" higher front sight if my max range is 100 yds?  Long range use is not a consideration so the cut horizon on the ARMS is not a factor.  Thanks

Yeah, I am going to build a rifle here soon hopefully, and there is no contest in price or functionality, get an ARMS 40.  Same price as a carry handle and 10 times better.

Quite a few people have said that they didn't need the .04 higher front sight post.

The standard A2 sight leaf doesn't compensate for sideways movement on the windage screw, so you can have your compromise up close or far away.  Quite a few people just order the standard A2 leaf with it, not the ARMS cut one.  They say that the cut leaves the top of the ring too thin and that it "ghosts".

My plan is to get an Ashley outdoors slight leaf.  Both big hole and small hole are zeroed to the same elevation and compensates for the windage screw shift.  Another $35 that would make it a little better.

Zero your flip up with the big opening.  If you ever had optics break down and REALLY NEEDED to shoot, you would probably be close enough that you would use the big hole.

That is just what they tell me on AR15 world!

I installed a, cutomized, A1 aperature in my #40, and it sighted in fine with my BM M4 barrel.

no freaking comparson, ARMS #40 is the only way to go.