What are the apeture sizes for M-16/M-4 family of weapons, and I mean MIL-SPEC.

Troy, little help here please, or anyone else.


[:)]

The M16 and M16A1 have a rear aperture of 2mm.  The Low Light Level Sighting System (early GI issue night sights) used a 2mm long range tang and a 7mm short range tang for use with the promethium front sight.

The M16A2 and M4 use a 2mm long range tang and a 5mm short range tang.  I've also seen references for the long range tang being 1.75mm, but the 2mm figure comes from the military and that's what you wanted.  

Ross

Thanx, I remember the M-16A1's having 2 different sized apetures, oh geez the memory is the first thing to go. We did have some front sights equipped with tritium, any idea how prevalent the 2mm/7mm rear sights were?

thanx

So for my information was one for short distance (0-200m), and the other for ranges further than 200m? There is lots of info on the A2 sights but I have never seen any info on the A1 sights.

  I have read the Colt handbook method for setting the sights on my A2 based on the 25 yard zero but had a Marine who was supposedly a firearms instructor tell me the large aperture was for low light shooting and the smaller one for day. He also told me that they (Marines), using the small aperture, zero their rifles at 200m. Hell..I can't see that far!

The A1 2mm/7mm was prevelant in the early 80's in some Infantry units.  Other than that, they really didn't exist.  There was really no point in cooks and cat skinners having night sights.  Remember there is an obvious cost that goes along with switching them out, and that's absorbed by the unit that orders them.  All units have a budget believe it or not.  Buying night sights means less of something else.  They weren't compatible with NVGs or other NODs so once those became commmon, they disappeared.  You can still find them for sale once in a while, and quite frankly it's a great rear sight.  The 7mm is a better close range sight than the A2 5mm short tang, and you still have the 2mm long range tang for aiming.  

The A1 is zeroed for 250M.  That's the short range tang up.  This will provide hits on a man sized target out to 325M without much, if any holdover.  The long range tang will be zeroed at 375M when you flip over to it.  This will allow you to hit a man sized target from 350-460M.  Below 350M the path of the bullet is actually above a man.  So in a nutshell, you use the short range tang to 325, and flip to long range after that.  An easy guide is the front sight is about the width of a man a 175M.  If the target is half the size of the front sight post (when aiming through the sights) the range would be 350M, and you should flip to the long range tang. (obviously it depends on the size of the target, but this is close enough for govt work)

The A2 is zeroed at 300M.  With NATO ammo the height of the trajectory does not exceed the height of a man out to 600M.  The short range (large aperature tang) is used for short range engagements, which are by nature faster.  It's also used for lower light, but it's only of limited value.  Once it get's dark you can't really see the sights anymore anyway.  The 0-200 is really there to remind you that it's only for short range work.  If you have the time to aim, use the smaller aperature tang, and adjust the range with the BDC dial.  Below 200M the big hole will be good enough because of the flat trajectory of 5.56mm.  

Obviously the M4 has a shorter sight radius which will change things.  They were just coming out when I got out, so I really don't know anythig about them

Ross

Thanx for the responses.