I've been shooting iron sights all my life. I'm 67. I shot smalkolbore competition as a kid and became an expert at zeroing an iron sight-equipped rifle. I just traded a Colt SP1 I've had since 1978, and another gun, for the above described rifle.

I am primarily interested in zeroing for close enocounters...0/200 yards.

The documentation in the handbook is poor and obtuse. I called Bushmaster customer service and got some macho guy who's personal communications skills left something to be desired.

His instructions directly contradicted those in the manual.

The rear sight has an elevation wheel that rotates. It has a setting that appears 6/3. The next click shows a small lstter "Z".

The manual says to begin, logically, at a range of 25 meters, with the rear sight set at "Z". It describes firing groups and adjusting the front sight until the group is brougnt into the bull. The flip-up aperature is supposed to be set at the longer range setting.

Then, after obtaining the proper group location, the manual advises me to rotate the elevation wheel tothe 6/3 mark for a 300 meter zero.

The guy at Bushmaster directly contradicts this. He advised me to begin zeroing at the 6/3 mark and to press on from there.

Since this rifle will serve as a home defense/vehicle defense wqeapon, it would seem to me that the shorter range rear sight aperature, almost a ghost ring with a larger aperature, should be used.

What should I do? Zero on the "Z" mark and then rotate counterclockwise to the 6/3 mark, as the book says, or zero at the 6/3 mark and then shoot for group using the ghost ring, or initially zero with the ghost ring at 100 yards at the 6/3 setting with the bullet strikes at about an inch high?

I've never seen something so apparently simple become so complicted.
Any pertinent advice will be deeply appreciated.

I've seen several different theories for correct BSZ with an AR. The one that makes the most sense to me is zero in the "Z" setting at 50 yards with a 16" rifle or 25 yards with a 20" rifle using the small aperture. Then set the dial-a-miss wheel to 6/3 and use the appropriate aperture for rapid or precision fire.

I've done so on my rifles and just shoot point of aim out to 200 yards and the bullet will stay close enough to let them know you're thinking about them.

On the original M16A1 the apertures were at different heights, with the A2 aperture they are both on the same plane, just different diameter openings.

YMMV but so far so good for me and my rifles.

Thanks. That makes sense. It's been too cold here all week to try it out, but tommorrow it should warm up enough to give it a try again.

If I'm gonna try to take something out at 600 yards, I'll drag out my Dakota 7mm Rem It performs flawlessy at that range. I'm more interested in what happens if I take the wrong turn in the city and run into an unhappy crowd.

I didn't know the aperatures are in the same plane. On my old Colt, they weren't. Thanks for the info.

Fred

jet,
Down and dirty.
Mechanical zero first:
1. Run the windage all the way to one side (til it stops) and count the clicks back all the way to the other side (til it stops). Divide by 2 and run it back that number of clicks to the middle. This is your mechanical windage zero.

2. Move the front site post until the base of the post is flush to the front site post housing. Move the rear site wheel to "z". This is your elevation mechanical zero.

For a 25M zero: Simply shoot center mass at that range with the small aperture and adjust as necessary, but adjust elevation using the fron post only. That will probably give you a zero somewhere on the other side of 100M as well depending on ammo/barrel.


There are other more useful zero methods out there if you anticipate adjusting elevation.

For home defense, skip both aperture and post. Sight thru the ears of the front and rear sight.
Don't forget your barrel offset indoors!!! Your sights are almost 2 inches above the bore line so make sure your muzzle is clear of cover even if you have a good site picture.

If you really want to mess with it, here is a link to some more useful zero methods:
ARFCOM's RIBZ method

quote:

Originally posted by jetdrvr:I am primarily interested in zeroing for close enocounters...0/200 yards.

Then you'd probably like about 2 or 3 clicks under your 3/6 zero! Easily done and the adjustments on your "dial-a-miss wheel" stay the same.

Jetdvr;

Set the elevation wheel at Z, zero to COM at 25 Meters, using the SMALL aperature (better sight picture). When Satisfied with your zero, turn the elevation wheel back to 3/6 (I am assuming this is an M4gery or CAR w/short sight radius and 16" barrel).

The only difference in zeroing with Z or 3/6 is that the Z range is 25m (standard Army zero range distance) and 3/6 is 42m with M855 ball, so you can zero at either 25 or 42, whichever is more convenient I guess. Both enable a carbine to be "on" at 42 and 300 m, with sights set at 3/6 (or 3/8 if a rifle). Insure you set the elevation to 3/6 once comleted, if zeroing at 25m.

Your carbine will be zeroed to strike POA/POI at 42 meteres and 300 meters, with a rising POI from 42 to about 275, dropping down to be back on POA/POI at 300M using M855 ball.

Note: if you shoot at ranges past 100m or so, zeroed thusly, your impact will be quite HIGH, especially as you range out to 250m, I mean 12+ or so inches at 225-250m.

This carbine is designed to allow "no sight change" hits on a human torso sized target from 0m to 300m when properaly zeroed (and using M855 ammo).

If you are certain that you max range will likley be, say, not more than 100m, zero it at 100m with the sight set at 3/6 and you'll be "on" from muzzle to about 150m (point blank diameter of about 4"-slightly low at short range, slightly high out to 150m.

Remember, these sights were designed with the trajectory of M855 ball ammo in mind, so your trajectory may vary dependent on weight, BC and velocity of the rounds you are using.

Choice of aperature size is up to your preference-but many use the 0-200 peep for field of view increases-if you are like me-presbyopic, using the small aperature helps see that front post better....

Contray to many "beliefs", M193 55 grain and M855 ball (milspec,not just similar FMJs) do very well in soft targets at milspec muzzle velocities.

http://www.razoreye.net/mirror...racle_Mirror.htm#762

best;

quote:

Originally posted by Andrew cempa:
Contray to many "beliefs", M193 55 grain and M855 ball (milspec,not just similar FMJs) do very well in soft targets at milspec muzzle velocities.

We had a rep from Winchester last year who wanted to show us how well his ammo worked. He brought a trailer with several blocks of ballistic gel to the range and the fun began.
We mainly shot handgun rounds but did get in some shooting with a 16" carbine in 5.56mm. He really wanted to sell the FBI load which features a Nosler partition at $1 per round. We issue the Winchester 64gr softpoint and it really does a pretty good job at a good deal less per round. The surprise was when I got out a box of plain old Q3131 55gr ball and shot it into the gel. You could see the track where it penetrated @4" and then flipped up just like Dr. Fackler says it will. It then blew apart and shredded the inside of the gel for about 10" in every direction. The Winchester rep and all in attendance were amazed at the destruction compared to all the other rounds we'd tested. It's good stuff if you're close enough for it to rotate and break apart.

RickR;

Yes indeed-as long as impact velocity is upwards of 2500 FPS, they yaw, tumble and fragment at the cannelure with rather impressive results. The benefit over soft point or expanding ammo is that they still do quite well at penetration of barriers such as equipment, IIIA and below body armor and moderate protective structures (windsheilds, car doors etc).

Of course, they do not do well on heavy clad or concrete block construction....

I have seen real results in far off places. Of course, any non-CNS hit with even a 338 lapua will still allow a motivated bad guy to fight for a while-so rapid multiple hits is required, just as with a handgun.

The idea that a 762x51 drops them while the 556 pisses them off is not proven in combat.... The 762 bores deeper before yawing, so all you get is a larger diameter throat, and usually no/little dynamic effect.

We are talking combat ranges from 0 to about 200 m.

quote:

Originally posted by Andrew cempa:

If you are certain that you max range will likley be, say, not more than 100m, zero it at 100m with the sight set at 3/6 and you'll be "on" from muzzle to about 150m (point blank diameter of about 4"-slightly low at short range, slightly high out to 150m.

Andrew, there's a better way to handle the short range stuff using POA/POI ....... and still keep the "dial-a-miss" wheel adjusted for those longer ranges if needed.

You can get more clicks downward by adjusting the two piece "dial-a-miss wheel". All you need is a 1/16" hex key. Figure out how many extra clicks down you'll need for the 100 yard zero.... and adjust by seperating and adjusting the two parts of the elevation drum using the elevation drum index screw.

PS - The term "dial-a-miss wheel" is the sole priority of RickR...... and I use it with his permission.......if he grants it!

DaMan,
I saw that technique several years ago on AR15.com and used it in my first M4orgery. It's a good system if you have the patience and skill to shoot decent groups and understand the principle.

Most of my guns now have a BUIS for irons without the elevation wheel and my most used carbine has an A1 style upper with an A2 sight installed.

I've seen a few guns come out of the cruiser or gun bag with the dial a miss moved by Mr. Murphy and I try to thwart him on my guns.

Most of our guys have carbines sporting big white blobs of paint or whiteout marking the proper sight adjustment so you can easily check while getting down to business.

Feel free to use that term to your hearts content.

jetdrvr

Here is another method.

With the small aperature, sight the rifle in at 100 yards, withn the "wheel" all the way down on 3/6 [or 3/8 depending on which wheel you have].

Then shoot at 200 yards, turning up the wheel until you are dead on. Repeat at 300 if you want.

Then if you want to be able to hit small targets up close, then shoot at 15, 25, 50, 75, and say 150, yards, turning up the wheel until you are dead on at each distance.

Just keep an accurate record of your comeups.

You will probably discover, that you wil be point of aim/point of imact "in the house" [ie up very close] when the wheel is all the way up, or very nearly so.

Basically you are using the wheel as Ballistic Cam, tuned to ranges more suited for sporting purposes.

At some distances you may find you need some windage adjustments as well to be perfectly dead on.

If you rifle has the standard small hole big hole rear aperature, then when you go to the big hole, it will move you down and left a fair amount at 100 yards.

You can dial up for this change as well.

Some guns now have same plane rear apperatures and point of impact is not changed.

At work after testing at varis ranges we decide about 1.5 inchs low at 25 dead on at 50 and apox 1.5 inchs at 100 dead on at 200 for are ARs.

If you site in dead on at 25 you'll be apox 12 inchs high at 200 dead on again at 350.

quote:

Originally posted by p dog shooter:
At work after testing at varis ranges we decide about 1.5 inchs low at 25 dead on at 50 and apox 1.5 inchs at 100 dead on at 200 for are ARs.

IF you have the M4 A3 carbine with the removeable carry handle........ and IF you set the 3/6 zero to strike dead on at 25m....... and you have adjusted the rear site drum as I described above to allow you to come down 3 clicks from that 3/6 zero...... then you'll have that 50 yard POA/POI zero.

PLUS....... your dial-a-miss will still be calibrated in meters!

Try it! You'll find this is the best way to do it.

FM 3-22.9

do a google search for "improved battle sight zero." it really works and gives you a genuine 100 yard zero without compromising the rifle's long range capabilities.

jtdvr

As you can see an answer is difficult unless you can tell us whether you have a M4 model or an M16A2 model. The difference is in the sight radius which effects the point of impact at 25 meters for a 200, 250 or 300 meter zero.

Larry Gibson

quote:

Originally posted by Larry Gibson:
jtdvr

As you can see an answer is difficult unless you can tell us whether you have a M4 model or an M16A2 model. The difference is in the sight radius which effects the point of impact at 25 meters for a 200, 250 or 300 meter zero.

Larry Gibson

Larry, I think jetdvr has the M4 type with A3 removable carry handle sights. These sights are advertised as having 1/2 MOA elevation value per click on the elevation wheel vs. the supposed 1 MOA of the A2 fixed handle carbine sights.

I've found that the shorter 14.5" sight radius on my A2 sighted carbine (16" bbl.) moves the POI about 1.4" per click of elevation at 100m. So I would guess that .7" per click of elevation at 100m could be expected with the A3 sights.

It's really pretty damn simple once you understand the concept and know the elevation values of your particular sight.

DaMan

I was just wondering because it does make a difference. The directions are simple but if you follow the directions for the wrong sight/rifle then all will not be well.

I agree with you that he needs to set the rear sight 2 clicks under the 3/6 zero setting and then use the front sight to get a 200 yards actual zero. With the rear sight set at 2 clicks under 3/6 and zeroing at 25 yards the POI should be around 1.35" below point of aim for a 200 yard zero. Of course a lot depends on the ammo used. Confirmation at the actual 200 yards is the only way to know for sure.

Larry Gibson

quote:

Originally posted by Larry Gibson:
jtdvr

As you can see an answer is difficult unless you can tell us whether you have a M4 model or an M16A2 model. The difference is in the sight radius which effects the point of impact at 25 meters for a 200, 250 or 300 meter zero.

Larry Gibson

I have the M4 model, 16" bbl, with 6/3 on the wheel.

I am shooting 55 grain ball. Finally got a good zero by using the smaller aperature over the 6/3 mark, putting me about 1.5" high at 100. Since that is the max range I have available, I can only assume that I should be good out to 300 or so. Please correct me if I am wrong.

Thanks, everyone.

I'd think you'll be "good to go" for anything you'd want to shoot with a 55gr bullet out of a 16" barrel with iron battle sights.

Stick a scope on that puppy and you can hit a bit further out, but the cartridge isn't realizing it's full potential from the sort tube.

How do you like the M4 compared to the 20" rifle?

quote:

Originally posted by Larry Gibson:
Confirmation at the actual 200 yards is the only way to know for sure.

Agreed! Confirmation at actual range with the chosen ammo is the best way to know for sure.

jetdrvr,
i have 19 ar-15 platform patrol rifles to keep up and running. the concern for the personell is 100 yards and closer. here is what we do. enlarge the close range apature to make a true ghost ring. turn the elevation all the way down to bottom on the frame. sight the rifle in with your prefered ammo using the front sight.cops are notorious for messing with things. if i take a gun out of the car i can see the rear sight is centered and down i know it will be well withing a minute of man and the officer can confidently use it. even at 200 yards the center mass of a man is in extreme danger.

quote:

Originally posted by Rick R:
I'd think you'll be "good to go" for anything you'd want to shoot with a 55gr bullet out of a 16" barrel with iron battle sights.

Stick a scope on that puppy and you can hit a bit further out, but the cartridge isn't realizing it's full potential from the sort tube.

How do you like the M4 compared to the 20" rifle?

I prefer it. It's actually more accurate than the old Colt SP 1, and it's a lot handier I can collapse the stock and stick it behind my trucks seat and use it out the window, if necessary. It swings better with the shorter barrel. Since I'm in an urban environment primarily, I don't anticipate using it past 200 yards, anyway, but I'm good out to three.

quote:

sight the rifle in with your prefered ammo using the front sigh

I did. With the drum set at 6/3, I used the front sight for elevation. I'm dead on at fifty and 1.5 high at 100. Since I only have a 100 yard range, I figure from the tables I'm good for M.O.M out to 300.

I've had a lot of old surplus stuff laying around for years. Some PMC and other stuff, I think Filipino, and it still groups at about an inch or a bit more at 50. Using higher priced fodder, I'm getting 1.5" at 100. I'm happy, and thanks for all the references and good advice. I hope to eventually scope it, but a sick pet is eating up my spare cash in vet bills now and it may be a while.