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boostmin
05-24-2011, 12:07 AM
I've been reading about USMC zeroing procedure and I am a bit confused.

I have 3 questions:
1. Where do I set my rear site to start?
2. Is it going to be a big deal if I zero at 25 yards as if it were 25 meters?
3. When it says "go to 6/3 -2 clicks", is "-2" up or down?

I have an A2 front sight and a removable carry handle that has a 6/3 setting and uses half-clicks (6 half-clicks between 6/3 and 4). When I lower the rear sight it stops short of 6/3, at a small "z" that is 1/2 way (3 half-clicks) between 6/3 and 4.

The procedure says I should start at 6/3 -2 and then turn it back to 6/3 when done, but I can't because my site stops at "z".

javalos
05-24-2011, 6:48 AM
I've been reading about USMC zeroing procedure and I am a bit confused.

I have 3 questions:
1. Where do I set my rear site to start?
2. Is it going to be a big deal if I zero at 25 yards as if it were 25 meters?
3. When it says "go to 6/3 -2 clicks", is "-2" up or down?

I have an A2 front sight and a removable carry handle that has a 6/3 setting and uses half-clicks (6 half-clicks between 6/3 and 4). When I lower the rear sight it stops short of 6/3, at a small "z" that is 1/2 way (3 half-clicks) between 6/3 and 4.

The procedure says I should start at 6/3 -2 and then turn it back to 6/3 when done, but I can't because my site stops at "z".

1. On a rifle length AR ("20"), set the carry handle on the Z setting. On an M-4 ("16"), set it on the 6/3.
2. Difference between 25 yards and 25 meters is 2.3 feet and it does make a difference from what I understand.
3. I think it was trying to say in procedure if you are zeroing a rifle length AR or M-16, you go back from the Z setting -2 clicks back to the 6/3 setting when you are done. Be aware that some carry handles are in half clicks and others are in full clicks.

PoofNoEyebrows
05-24-2011, 6:58 AM
On a full length rifle doing a BZO at 36 yards with your rear set at 8/3 (6/3 - M4 or A4) will get you on at 300. This is actually from CMC-22R:

A BZO is the elevation and windage settings required to place a single shot, or the center of a shot group, in a predesignated location on a target at 300 yards/meters, under ideal weather conditions (i.e., no wind). A BZO is the sight settings placed on your rifle for combat. In combat, your rifle’s BZO setting will enable engagement of point targets from 0 – 300 yards/meters in a no wind condition. (Note that 8/3 is the rear sight elevation knob setting for the M-16A2 BZO. 6/3 is the rear sight elevation knob setting for the M-16A4 & M-4 Carbine.)

Call_me_Tom
05-24-2011, 8:51 AM
USMC uses 36 yards for a 300 yard zero. The Army uses 25 meters for a 300 meter zero. You can't use 25 meters or 25 yards to obtain a 300 yard zero.

dieselpower
05-24-2011, 9:04 AM
You are confusing two zeroing procedures. IBZ and USMC.

Click my TM9-1005-319-10 link which is the ARMY M16 field manual. It has the USMC procedure in it also.

your rear BUIS should bottom at 6/3, two clicks lowers the point of impact to align it at 25 meters, then going back to 6/3 is your 600/300 meter zero.
http://i655.photobucket.com/albums/uu272/Wiringguy/Zerobulletpaths.jpg

Once you master this, you can read up on the Improved Battle Zero at 50 yards and adjust the mechanical stop on your rear BUIS to give you a proper 50 yard zero.

Hope this helps

HighLander51
05-24-2011, 9:18 AM
Call_me_Tom,USMC uses 36 yards for a 300 yard zero. The Army uses 25 meters for a 300 meter zero. You can't use 25 meters or 25 yards to obtain a 300 yard zero.

That is correct. 50 yard zero will zero again at 225 yards (55 grain).

Most competition 3 gun shooters run the 36/300 yard zero. Some run 28/350 or 23/400, depends on target size and home range. The long zero is of course more important than the close zero.

http://www.box.net/shared/static/xuhqpttxnv.jpg

dieselpower
05-24-2011, 9:41 AM
Yeah there are two schools of thought.
1) A 25meter zero gives a better distant engagement since it requires less hold over. With a 500 meter/yard threat that you must return fire at, with a 25meter zero your hold over is minimal. When closing that gap your POA (point of aim) is at the worst 10" (target 200 yards away), your MOA of the AR15 carbine + the MOA of the optic/BUIS means your POA is nearly your Point of Impact (POI) anyway. All things being equal with a target 200 yards away, you aim for the gut, you hit the chest. The fact you can see your impact is an added benefit. Your impacts are above your aiming point.

2) The 50 meter/yard zero has a flat trajectory. Forget AT&T shots, thats not your main use of the carbine. The majority of your threats and engagements are within 200 yards. The best fragmentation of your ammo is 200 yards. With a 50 yard/meter zero where you POA is where you POI.

Choose whats best for you and your optic.

HighLander51
05-24-2011, 9:46 AM
dieselpower, Choose whats best for you and your optic. Agree, depends on what 'window' size your target presents. My .223Rem bolt gun is set differently than my AR-15's.

dieselpower
05-24-2011, 10:03 AM
dieselpower, Choose whats best for you and your optic. Agree, depends on what 'window' size your target presents. My .223Rem bolt gun is set differently than my AR-15's.

I agree and disagree with that. The window size has zero to do with how I zero my firearm months or years before that encounter...which is why you have two rifles..LOL

I see many guys carry the M1A and a M4A1 for this reason. People still need to choose how they set up that carbine.

Ignore everything past the 250 yard mark. You still have two zeros which require a different mindset before hand.

For me, I carry 1 rifle. I have a 4MOA Dot, non-magnified. At 200 yards, my Dot covers 8". My 25meter zero mixed with my 8" dot tells me my POI will be on the top edge of my dot. I place the dot on the target, my bullets with strike on the top edge (quadrant) of that aiming point.

If i had a 2MOA dot, I may choose the 50 meter. the dot is considerably smaller. This still doesn't allow for the MOA of the rifle, nor my ability to hold steady on a 4" "window" as seen from 200 yards away.

That drawing of yours is OUTSTANDING as a training aid. It needs 1 more thing. I may steal that from you and add it. The POI/POA/MOA of the RDS LOL

akjunkie
05-24-2011, 10:49 AM
Great thread. Glad everyone is chipping in and keeping it civil.

Always wondered why there were so many different "standard" ways of zeroing for the Army and USMC.

saint7
05-24-2011, 11:08 AM
LOL... because both are always trying to see who has the bigger pecker size.

Semper Fi!

Droppin Deuces
05-24-2011, 11:22 AM
My rear sight doesn't click at "6/3." It clicks at 6 and again at 3. Does that mean it's a 1/2 clicker? I always zero the rifle at 25 on the 3 and get great results at ~300 yards.

HighLander51
05-24-2011, 11:32 AM
saint7 LOL... because both are always trying to see who has the bigger pecker size.

No, that's why I never worry about carrying a loaded Glock appendix style, the chemo therapy took care of that problem years ago.......

For the last 7 years I have been running a Trijicon Accupoint 1-4. The greatest amount of eye relief on any scope ever. The pinpoint reticule takes a little getting used to, but it is fast. I keep a graphic on the rifle buttstock that shows holdover from 0 to 350 yards.

http://webyshops.com/ns/images/Trijicon/TRIJICON-AccuPoint-1_25-4x24-Riflescope-Red-Triangle-Reticle-TR21R-Pic1.jpg

1911su16b870
05-24-2011, 12:40 PM
Some additional info from arf com on the Revised Improved Battle Zero...

http://www.ar15.com/forums/topic.html?b=3&f=18&t=328143

Only difference is for the M4 6/3 sights they have double clicks (4 in lieu of 2) past 6/3.

boostmin
05-24-2011, 2:39 PM
Wow, lots of great info.

Where can I zero my rifle at the correct distance (since the range by me only goes 25yds)? I'm in OC.

dieselpower
05-24-2011, 3:42 PM
If someone spots an error with this tell me. Sorry this is so small. Imageshack is downsizing it.

I will take it down and try to fix it. I am doing 10 things at once and didn't check everything. The math is a bit fuzzy anyway. 1 MOA is not a true inch, and all barrels have a different error due to button rifling, cut rifling, twist 1:7, 1:7.25, 1:8 ..blah blah blah

You can see as your target gets farther away, your POA/POI/MOA all stay at a relationship to your zero. This is why the Army and USMC all zero about 25 meters. With a 2 or 4 MOA RDS you can see the relationship of the POI to your POA. The 50 yard zero is great for those guys who are not going to pull the trigger on something over 350-400 yards away.

This is also why the 5.56x45 is not the best choice for 500 yard threats.

I like the 25 meter zero since I can deal with being a bit high. I like to see my target. I just do a Hold-Under not Hold-Over.

http://img714.imageshack.us/img714/7025/trajectorydisplay2.jpg

Knife Edge
05-24-2011, 3:48 PM
You are confusing two zeroing procedures. IBZ and USMC.

Click my TM9-1005-319-10 link which is the ARMY M16 field manual. It has the USMC procedure in it also.

your rear BUIS should bottom at 6/3, two clicks lowers the point of impact to align it at 25 meters, then going back to 6/3 is your 600/300 meter zero.
http://i655.photobucket.com/albums/uu272/Wiringguy/Zerobulletpaths.jpg

Once you master this, you can read up on the Improved Battle Zero at 50 yards and adjust the mechanical stop on your rear BUIS to give you a proper 50 yard zero.

Hope this helps

Excellent!!

HighLander51
05-24-2011, 7:24 PM
It's a bit fuzzy, but you get the idea. Taped to the left side of my rifle buttstock. Where to hold to get zero from 0 to 350 yards. 18" compensated running 55-62 grains. Zero at 36/300 yards for a 10" window.

http://www.californiavtxriders.com/phpBB3/gallery/image34955.jpg

Justintoxicated
05-24-2011, 7:46 PM
I zerod in at 100 so I can use the BDC reticle on my nikon :P

Guess that makes me a cheater.

Army
05-24-2011, 7:49 PM
Just blast rounds downrange until you hit something :)