The only complaint most have about the 40L is that it defaults to the small aperature.  Point well taken.

Lots dont like the Arms 40 with the notch because the notch takes away from your sight picture and eliminates part of the Ghost ring principal.  Ive never seen this, but I can see how it happens.  The Idea of a 600 yard mark on the small apperature is a good one, its just not good when it takes away from the effectiveness of the sight.

MY PROPOSAL.  Why doesnt someone make the 40L's small aperature be cut like the 40 with the 600 yard reference.  Someone could use the milled section for long range shots when needed.  The problem of the notch washing out the ghost ring is remedied by just leaving the two aperatures folded together.  The top of the 0-200 aperature would cover the notch cut into the 300 meter aperature.

The best of both worlds, but still no fix to the 40L defaulting to the small aperature.  For Armchair comandos like myself though. theres not real drawback.

BTT, plus after I think about it, you could leave the long range aperature down since its got the notch to clear an ACOG, and the sight will be defaulting to the 0-200 aperature.

With the #40L you can take out the small apeture part and it will default to the large apeture.  But if you do that you will not have the small apeture as an option.

Should I get the #40 or the 40A2?

Quoted: Should I get the #40 or the 40A2?

40A2

What's the difference between a 40A2 and a 40A?

I have never used that large aperature to qualify. If your up close and personal you'll probably be looking over the sights anyway, not worried about your BUIS. From 50M and further the small ring is plenty quick and muchy more accurate, therefore I prefer, and think the 40L is superior because of its default aperature, not to mention its size.

Quoted: What's the difference between a 40A2 and a 40A?

40 has a notch cut out of the long range aperature thats supposed to double as a 500/600 sight.  Its really just the way they had to cut it to fit under an ACOG

40A2 has a completely standard and unmodified A2 aperature

40L has the custom fold together aperatures.

40A2 is best for anybody unless your fittig it under an  ACOG mounted to a flattop.  Even them I think the A2 barely fits.  The 40 with the notch has like 1/10 inch of space between the sights and the ACOG.