AR-15 Zeros and Trajectories

[danco]

Highly recommend just going point of aim/point of impact at 100.

Why? So that you're low at every range but 100 yards?

Pardon my ignorance, but looking at the ballistics charts tells me that if you zero for 100 yards/meters, that's it...you're at the top of the parabolic arc.

When you zero for 25/300 or 50/200 (your choice), you're high between these distances, but not by more than 8"-10" (with a 25 zero) or 4"-5" (with a 50 yd zero)...

Am I missing something?

Edit: Maybe I am...Reading your "Zen of 100m Zero" now...Maybe I'll learn something! :-)

[Cincinnatus]

Why? So that you're low at every range but 100 yards?

Pardon my ignorance, but looking at the ballistics charts tells me that if you zero for 100 yards/meters, that's it...you're at the top of the parabolic arc.

When you zero for 25/300 or 50/200 (your choice), you're high between these distances, but not by more than 8"-10" (with a 25 zero) or 4"-5" (with a 50 yd zero)...

Am I missing something?

Edit: Maybe I am...Reading your "Zen of 100m Zero" now...Maybe I'll learn something! :-)

The arc is not a rainbow. It's a difference of within six inches or so, depending on what distance one is shooting. Well within the accuracy requirements for minute-of-badguy in a defensive carbine--Unless one seriously thinks you're going to be using your rifle to take out a hostage-holding terrorist at 400m. )

[danco]

Looking over Failure2Stop's Zen of the 100 Meter Zero, I must admit it makes a lot of sense. I'll have to give it a try.

~Dan

[Pimpin007]

Thanks Molon alot of great info in one thread so I don't have to search for it on the web.

[KarbonChemist]

This is a FANTASTIC thread. Tons of useful info.

[initialkev]

If you put the barrel parallel to the ground and the bore axis perfectly centered on the bulls eye at a 100 yards, how much will a 55gr bullet drop?

[Failure2Stop]

If you put the barrel parallel to the ground and the bore axis perfectly centered on the bulls eye at a 100 yards, how much will a 55gr bullet drop?

http://www.jbmballistics.com/cgi-bin/jbmtraj-5.1.cgi

[Doc. Holiday]

There are a bunch of ballistic calculators out that that can help you figure that out including Apps for your phone.

[7 RING]

Thanks Molon. I have been running a 200 yard zero on my AR-15s for about 30 years with good results. About 10 years ago I read an internet post by a US Marine Corps officer, his name was Sanchez I think, and learned to reset the rear sight elevation knob like you showed on your post. I can shoot neck hold at 300 yards or come up 3 minutes to the 300 yard setting and shoot POA with good resuits.

I am going to check out Failure2Stop's Zen of the 100 Meter Zero and give that a try. Sometimes you can teach an old dog new tricks.

[rlodi1911]

I k ow tho thread is as old as can be, so ill just ask an hope the best. I'm hoping for the 100 yrd and my Matech BUIS lowest setting is 200. Are these instructions on how to adjust the rear sight applicable for the MaTech BUIS as well or is there another scheme I should apply to get this particular rear sight set to zero at 100. I like the 100 yard due to my only concern should be hold over (and not under). Well, her's me wishing for a reply on a older than dirt thread. I'm just hoping enough people (like me) are referred to this thread tht I might find one person who an lens their guidance