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1/22/2020 12:12:56 PM
Posted: 9/14/2009 2:34:39 PM EST
OK, so I'm curious as to how everyone here zeroes their A1's. I've got one completed A1 rifle here so far, but I replaced the A1 aperture with the A2 when I put the upper together. When I zeroed the rifle, I zeroed it for 200meters with the small aperture ala the "Marine Improved Battle Sight Zero". I used that zero because I figured I would take advantage of the relatively flat trajectory of the cartridge. IIRC, it's less than 2 inches above the line of sight most of the way to the 200m point, and only 2 inches below at 250 meters. Thats plenty of distance for me to play with without worrying much about adjusting or fudging for impact point, and with an A2 aperture I've got a large hole that's great for, uh, hunting and stuff, and a small hole for target shooting.
The A4 carry handle on my HBAR is set using the same zero and the 3/6-4 trick.

But now I'm wondering, how would a 300m zero work with the A1 rifles? Supposedly it shoots too high with the A2's but I don't know if thats speaking purely about having the rifle in battlesight zero mode (Either hole, 3/6 or 3/8 rear sight settings), or if that includes all of the range adjustments?

So, what do you think of the 200m zero, and how are your retro rifles configured in terms of aperture and zero?
Link Posted: 9/14/2009 5:18:21 PM EST
[Last Edit: 9/14/2009 5:36:32 PM EST by DakotaFAL]
Back in the day when I shot an M16A1, I was a big fan of the 300m zero. It made sense as the targets are people sized.

Since the mid course trajectory from 100-250m was between 5 and 7 inches high, you could aim center of mass to 350 meters and get a reliable hit if you did your part. If you only had a head shot at 75-250m you just held 4-6 inches low - essentially on the base of the neck. At 350-400 meters you could flip up the LR aperture and again shoot center of mass. Alternatively you could hold 6" to 15" high if you did not want to switch apertures. Not switching also made sense as on a full torso at 350-400m, you just held on the base of the neck again to get the rounds center of mass. Very quick, very simple and it allowed you to engage targets accurately and quickly from 25-400m.

If you are shooting with a ghost ring aperture however, it will limit your options a bit. A ghost ring aperture is great in low light conditons but it has some downsides. At that time we had 2 small apertures and we were trained to shoot with both eyes open. Consequently the small aperture was not an issue in target acquisition at close range and at night you still shot the same way basically seeing over/around the carry handle. In that regard it was not much different that snap shooting over the sights with an M14.
Link Posted: 9/16/2009 2:34:41 PM EST
Ok...I know I am not the only guy with an opinion on zeroing an A1.
Link Posted: 9/16/2009 4:24:19 PM EST
Actually, I'm starting to think that nobody here shoots their retro rifles. They just build them and take pictures.

A somewhat not-retro question... When I went to re-zero my A4 according to the Marine IBSZ (Rear sight four clicks below 6/3, small aperture, 50 yards) I pretty much ran out of elevation on the front sight, I think...
Is it normal or OK to have the "base" of the front sight post above the flat top of the front sight post? As I have the rifle now, the bottom of the post's base is just BARELY below the level of the front sight tower. Exactly how high can these things go?
Link Posted: 9/16/2009 4:27:47 PM EST
I zeroed my early 604 a while back at 50 yards and it shot true at 200. I don't really remember exactly what the steps to get there were, but it worked.
Link Posted: 9/16/2009 4:42:49 PM EST
I zero my ARs at 100 yards.
My HK51 is zeroed at 50 yards.
I zeroed my .50 BMG at 300 yards.
Link Posted: 9/16/2009 7:56:51 PM EST
I zero my A1s at 25. Actually I zero all my ARs at 25 since its what I am used to.
Link Posted: 9/16/2009 8:22:02 PM EST
I zero mine at 50. Walking all the way to the 100 yard line to retrieve my targets is too far! I've been rethinking it though and 25 is looking pretty damn good.

Really though, I use 50 because of the trajectory, +/- 2" out to about 230, if I recall. Point blank being the worst at -2.5". I shoot 100 yards or less, so this is good for my needs. If I was shooting farther, I'd reconsider.

Why did you use 6/3 - 4? Do you have half clicks between the settings on your A2? If -4 t is correct for your sights and you are concerned about the front sight you could consider a taller post. I think Bushmaster sells a .040 taller post.

Here is a interesting article on a variation of the IBZO. It is more of a LE application than a military one.

http://www.policeone.com/police-products/firearms/accessories/sights-scopes/articles/1298015-Sighting-choices-for-your-patrol-rifle/

And here is what I used for the IBZO when I had an A2 (I got rid of it after the last poll) Nothing new - but I reread it every once in a while.

http://grburnett.us/guns/ImprovedBattlesightZero.pdf

If you have an Iphone there are a few ballistics calculator applications that are fun to mess around with. Handy at the range, too.
Link Posted: 9/17/2009 12:06:02 AM EST
[Last Edit: 9/17/2009 2:12:00 AM EST by Der_Hans]
RLR - Yup, thats the method I followed all right...Guess I need to call Bushmaster up for a new front post.

I guess this also means that tritium night sight posts don't fit this rifle?

Edit to add rant: I've F!@$ING HAD IT WITH DETACHABLE CARRY HANDLES! Why is it that the A1 that I put together in my basement with a few tools and damn near no clue as to what I was doing was zeroed in with only three clicks of windage adjustment from center, but my A4 'match grade target' rifle needs to be re-zeroed every time I so much as look at it funny, AND needs a new front post!?
Link Posted: 9/18/2009 4:11:54 AM EST
Originally Posted By KJB:
I zero my A1s at 25. Actually I zero all my ARs at 25 since its what I am used to.
Zeroing an A1 at 25 meters with M193 or something very close will get you very close to a 300 meter zero. The difference will usually be less than, or not much more than one click up or down on the front sight post. With the A1, we would do the initial zero at 25 meters and then just check it at 300 meters to confirm.

At 25m you have to be dead center with a very small group as even a 1/4" error from center will result in a 3" built in error at 300m.

The A1, A2 (or any rifle with a significant distance between the sight line and the center of the bore) is susceptible to significant errors if you cant the rifle away from the vertical. That can be masked with a 25m zero as the effects will not show up until you begin to reach out to longer ranges.

Think of it this way...if you lean the rifle to the right so that the top of the front sight post is to the right of the center of the bore, the line of sight has to be angled to the left to intersect the line of flight of the bullet at 25m. The line of sight will maintain the same angle so the line of sight will be farther and farther to the left of the line of flight of the bullet as the range increases. So if you cant the rifle to the right, you will end up shooting to the right of the point of aim and vice versa.

Canting errors increase as the range increases but also, the error is more pronounced with a short zero range. If the sight is 1/4" to the right of the center of the bore, and I zero at 25m, I have to have enough angle on to get the line of sight to converge with the line of flight in only 25m - a fairly sharp angle that then maginifies the canting error at longer ranges. If on the other hand, I can confirm the zero at 300m on a no wind day, I only have to have an angle large enough to make up the 1/4" distance in 300m so the angle is much smaller (1/12 as small) and the canting error commensurately less.

Also, since the front and rear sight adjustments are perpendicular to each other, but are not centered over the bore, a sight adjustment for a horizontal change will also have a vertical vector and any vertical adjustment will also have a horizontal vector and those errors also increase as the range increases. So again with a baltle sight equipped rifle where sight adjustment is minimal, you want to keep the angles and errors small by at least confirming the zero at your maximum battle sight range, because everything less than that will have a reasonably small degree of error even if you cant the rifle slightly.

What it all means is a 25m or 50m zero is fine, but you need to confirm it at longer ranges.

In the immediate wake of Vietnam where the focus was still more or less on short range engagements, none of that was taught in basic marksmanship courses. My opinion was that this contributed greatly to troops missing at longer ranges due to a combination of a reliance on a 25 m zero with longer range shooting only on pop up silouettes and a lack of awareness of what results from canting the rifle. We would have had much better shooting at longer ranges under field conditions if troops had been conditioned to be aware of the importance of having the rifle in as close to aperfectly vertical position as possible. And, the M16A1 would have had a better reputation for accuracy as nearly all of them were capable of 1-1.5 MOA accuracy with M193 and iron sights if the shooter does his part.
Link Posted: 9/18/2009 4:45:54 AM EST
Originally Posted By KJB:
I zero my A1s at 25. Actually I zero all my ARs at 25 since its what I am used to.


This.
Link Posted: 9/18/2009 6:07:37 AM EST
I have all my A-1's zeroed @ fifty yardish meters. Also, the A-2's in the stable are zeroed @ fifty meters. I have the BUIS on my M4gery zeroed @ 50 meters. I guess thats unanimous for me.
Link Posted: 9/18/2009 8:48:43 AM EST
Originally Posted By Der_Hans:
Actually, I'm starting to think that nobody here shoots their retro rifles. They just build them and take pictures.


+ 1 here...
Link Posted: 9/18/2009 9:11:29 AM EST
Originally Posted By Der_Hans:
Edit to add rant: I've F!@$ING HAD IT WITH DETACHABLE CARRY HANDLES! Why is it that the A1 that I put together in my basement with a few tools and damn near no clue as to what I was doing was zeroed in with only three clicks of windage adjustment from center, but my A4 'match grade target' rifle needs to be re-zeroed every time I so much as look at it funny, AND needs a new front post!?


Simplify young man, simplify.

I zero mine at 100 yards, 'cause that's what I've got. And at my age, my eyeballs have started turning to granite.

Link Posted: 9/18/2009 9:24:21 AM EST
Originally Posted By Der_Hans:
Actually, I'm starting to think that nobody some here shoots their retro rifles. They just build shoot them and take pictures. ....











Link Posted: 9/18/2009 12:26:23 PM EST
[Last Edit: 9/18/2009 12:32:51 PM EST by DakotaFAL]
Originally Posted By MarkRSims:

Simplify young man, simplify.

I zero mine at 100 yards, 'cause that's what I've got. And at my age, my eyeballs have started turning to granite.

I agree it is easist to use the range you have, but that does not limit the range you can zero the rifle for.

For example:

I had a range in the back yard that was 100 yards in lenght - 100 meters would have been just past the neighbor's fence. 100 yards is 92 meters, and setting an A1 up for a 300 meter zero with M193 (or an equivalent load - a 55 gr FMJ BT with a BC of .237 at 3250 fps) just requires zeroing it 4" high at 100 yards.

At 25 yards (23 meters), you'd zero with the same load 0.5 inches low at 25 yards to get a 300 meter zero.

At 25 meters, you'd zero it 0.33" low - or alternatively just zero it dead center at 25m and then raise the front sight post 1 click / 1 MOA to get the 300 meter zero.

Now as for old eyes, 25 years ago shooting 1 MOA with iron sights was no big deal, but now it is a bit more of a challenge and I can use all the help I can get. If my A1 is zeroed for 300m, it shoots 4.0" high at 100yards - which coincidentally just happens to be half the diameter of the black on a 100 yd yard small bore rifle target. Consequently with a 300 meter zero I can use a 6 o'clock hold and hit in the center of the bull. My eyes will handle the greater contrast of a 6 o'clock hold a whole lot more accurately than they will trying to split the exact center of the black bull with the black front sight post.


Link Posted: 9/18/2009 7:21:27 PM EST
Sighted in my XM16E1 at 50 yards, since the range didn't allow 25 yard rifle practice. Of course, they also required that you shoot a pistol at no less than 25 yds - not too practical IMO. Now that I have the Colt 3X sighted in, I hate to pull it before I shoot it at least once more, then I'd like to run some 25m close quarter drills then throw it back on and see if it zeros. I wanted to zero it at 25M (30 yards or so?) for the 300 meter zero, which seems like it would be flatter shooting, but we played the cards we were dealt and started at 50yds. It will definitely get rezeroed, but I'm bumping my range post to show that people actually DO shoot their retro rifles occasionallly. Had a blast and want to get out more. MORE. MORE!
Link Posted: 9/18/2009 8:02:41 PM EST
50 yards is actually a great zero distance with the A2 aperture, not sure with the A1 aperture.

If you zero at 50 yards, the trajectory is no more than 2 inches above or below point of aim from 0 to about 250 meters. It's the "Improved Battle Sight Zero", it's just that you don t have an A2 range wheel to jack around with.
Link Posted: 9/19/2009 3:53:19 AM EST
Originally Posted By Der_Hans:
50 yards is actually a great zero distance with the A2 aperture, not sure with the A1 aperture.

If you zero at 50 yards, the trajectory is no more than 2 inches above or below point of aim from 0 to about 250 meters. It's the "Improved Battle Sight Zero", it's just that you don t have an A2 range wheel to jack around with.


The difference between the short and long range apertures on the A1 is about 0.014", 2.3 MOA, and the change in point of impact is about 2.5" at 100 yards.

If you are zeroed for 300m with the short range aperture, the long range aperture will be zeroed for 370m. As such the LR aperture will shoot about 4" high at 350m and about 7" low at 400m.

With a 50yd / 46m zero, the bullet will pass back through the line of sight at about 185 yd / 170m. and will be about 1.7" low at 200m, so it is ball park close to a 200m zero. (moving the front sight post down one click will leave you 3/4" high at 200m.) With a 50 yd zero, the LR aperture will then be zeroed at about 235m or 256 yards and you will be 10" low at 300 yards and 14" low at 300 meters.

In either case the LR aperature does not really add much range. In the A1 the intent was to push the zero range out to 250-300m with the short range aperture and then allow the shooter to get another 100m in effective range.

When zeroed for 300m the mid range trajectory will be 7" to 8" in the 150-225m range and will be about 7" to 8" low at 350m, allowing the solider to aim center of mass and get a solid hit in most cases. (at shorter 100-200m ranges, you'd hold 6"-8" low on a head and shoulders shot). Then with the LR aperture, you will be about 4" high at 350m, 7" low at 400m and 23" low at 450m - enough to still hit a standing soldier in the torso if you hold at shoulder level. In other words it worked well considering the size of the target. out to 400m and could be stretched a bit to 450m.

With a 200m zero, you gain a lot in terms of precision on the front end as the mid range trajectory is only about 2.5" high, but you are 2" low at 225m , 4" low at 250m , a foot low at 300m and 2 feet low at 350m. The LR aperture would then be zeroed at about 275m, and would be 2.5" high at 250m, 3.5" low at 300m, 8" low at 325m, 13" low at 350m and 2 feet low at 400m., so you in effect lose 75m in effective range.

But if you plan to shoot at ranges of 300m or less, you can use the 200m zero and then switch to the LR aperature at 225m and shoot to 300m without ever being more than 2-3 inches above or below the point of aim.

To get a 200m zero with an A1 and M193, you would shoot 0.9" low at 25 yards, 0.4" high at 50 yards or 2" high at 100 yards.

Link Posted: 9/19/2009 5:07:54 AM EST


Anyone have a .pdf of the target that could be printed out on a home printer? or is it greatter than 8 1/2"x 11 (or 14")?
Link Posted: 9/19/2009 5:57:06 AM EST
Well I can’t say much on how to zero an M16a1, but I can tell you how we currently zero the M16A2 (Yes some of use still use those), and the M4 in the Marine corps. When you first Zero your rifle for the 200-500 meter course of fire, you zero it at 200M with the sights set to 8/3-2 (So take your A2 sight to 300m, then to clicks down from that), zero the weapon. Now here is were it gets tricky, for the Battle sight zero, all Zeroing is done at, I think 32m, with the sight set to 8/3 (300m). The idea is that the trajectory of the round will be the same elevation at 32m as it will be at 300m ( round trajectory, it goes up then comes down). If you don’t zero your sights like this it makes all sight adjustment not relevant, because the sights are set for 100m increments. So if you zero at 50 or 25 yards with sights on 8/3 (300M) you may need a calculator to adjust your sights for 500m.

Hope this helps, to any Marines that qualified without optics recently, feel free to interject
Link Posted: 9/19/2009 7:49:33 AM EST
Sounds like not much has changed with the A2.

The ballistic coefficient of M855 is higher (.304) and the velocity is a bit lower (about 3150 at the muzzle in a 20" barrel.) but the higher BC will tend to make up for the lower initial velocity as it will retain more velocity at longer ranges.

The sight on the A2 allows enough vertical sight movement to fire to point of aim beyond 350m, but a 300m zero still makes sense for the same reasons at ranges under 300m.

Link Posted: 9/19/2009 9:12:47 AM EST
Originally Posted By LonghunterCO:

Anyone have a .pdf of the target that could be printed out on a home printer? or is it greatter than 8 1/2"x 11 (or 14")?


Here's one:

M16A1 25 M ZEROING TARGET
Link Posted: 9/19/2009 11:35:40 AM EST
Originally Posted By AKARS:
Originally Posted By LonghunterCO:

Anyone have a .pdf of the target that could be printed out on a home printer? or is it greatter than 8 1/2"x 11 (or 14")?


Here's one:

M16A1 25 M ZEROING TARGET


What's interesting about that target is the mention of M855 ammo being it's an M16A1 target.
Link Posted: 9/19/2009 12:11:21 PM EST
Originally Posted By AKARS:
Originally Posted By LonghunterCO:

Anyone have a .pdf of the target that could be printed out on a home printer? or is it greatter than 8 1/2"x 11 (or 14")?


Here's one:

M16A1 25 M ZEROING TARGET


Thanks!

Link Posted: 9/19/2009 7:15:06 PM EST
Originally Posted By crewcheif:
Well I can’t say much on how to zero an M16a1, but I can tell you how we currently zero the M16A2 (Yes some of use still use those), and the M4 in the Marine corps. When you first Zero your rifle for the 200-500 meter course of fire, you zero it at 200M with the sights set to 8/3-2 (So take your A2 sight to 300m, then to clicks down from that), zero the weapon. Now here is were it gets tricky, for the Battle sight zero, all Zeroing is done at, I think 32m, with the sight set to 8/3 (300m).


Setting the rear sights at 8/3-2 (8/3-4 for carry handles) is correct for both 200m and for the 50 yard crossover to obtain a 200m zero.

Originally Posted By DakotaFAL:
To get a 200m zero with an A1 and M193, you would shoot 0.9" low at 25 yards, 0.4" high at 50 yards or 2" high at 100 yards.


Iiinteresting...I'm going to remember this one!

Oh, about my carry handle issue...I spoke to a very helpful gent at Bushmaster, whom I've spoken to several times before, and he informed me that my rifle was not built with an "F marked" FSB...Which is the popper FSB for a flat top. This means that I'll need (And I HOPE its tall enough!) the longer front post, which he said he'll send for free. .03 of an inch sounds like NOTHING to me, given the drastic difference its going to need to make. The other thing that I'm pissed about is that this means that night sights are probably out of the question too. Provided that I can zero it, I'll be happy enough, but I'll remember that next time I buy a flat top, IF I buy another flat top.
Link Posted: 9/20/2009 4:24:00 AM EST
With the A1 you can check the mechanical zero of the weapon by adjusting the front sight post so that the base of the post is flush with the front sight block, then turn the rear sight all the way to the stop and come back 17 clicks to center it. With the weapon bore sighted at 25m, the sights should be close to the center of the target - if not, you have a problem somewhere.
Link Posted: 9/20/2009 5:42:20 AM EST
Link Posted: 9/20/2009 7:48:05 AM EST
Originally Posted By Der_Hans:
Originally Posted By crewcheif:
Well I can’t say much on how to zero an M16a1, but I can tell you how we currently zero the M16A2 (Yes some of use still use those), and the M4 in the Marine corps. When you first Zero your rifle for the 200-500 meter course of fire, you zero it at 200M with the sights set to 8/3-2 (So take your A2 sight to 300m, then to clicks down from that), zero the weapon. Now here is were it gets tricky, for the Battle sight zero, all Zeroing is done at, I think 32m, with the sight set to 8/3 (300m).


Setting the rear sights at 8/3-2 (8/3-4 for carry handles) is correct for both 200m and for the 50 yard crossover to obtain a 200m zero.

Originally Posted By DakotaFAL:
To get a 200m zero with an A1 and M193, you would shoot 0.9" low at 25 yards, 0.4" high at 50 yards or 2" high at 100 yards.


Iiinteresting...I'm going to remember this one!

Oh, about my carry handle issue...I spoke to a very helpful gent at Bushmaster, whom I've spoken to several times before, and he informed me that my rifle was not built with an "F marked" FSB...Which is the popper FSB for a flat top. This means that I'll need (And I HOPE its tall enough!) the longer front post, which he said he'll send for free. .03 of an inch sounds like NOTHING to me, given the drastic difference its going to need to make. The other thing that I'm pissed about is that this means that night sights are probably out of the question too. Provided that I can zero it, I'll be happy enough, but I'll remember that next time I buy a flat top, IF I buy another flat top.


You can also buy a DPMS carry handle which has about .060 lower adjustment that USGI. This allows for a proper zero without the taller post when using flattop carbines with standard FSB. Do this and you can use a standard night sight.
Link Posted: 9/20/2009 11:46:13 AM EST
What is the effect of using an A2 aperture in an A1 sight, BZOing at 36/300 with the small (unmarked aperture) and then flipping it to the 0-2 aperture? Is the 0-2 still effective for 0-200m like it would be on an A2 sighted rifle or carbine?
Link Posted: 9/20/2009 12:55:20 PM EST
Originally Posted By KJB:
You can also buy a DPMS carry handle which has about .060 lower adjustment that USGI. This allows for a proper zero without the taller post when using flattop carbines with standard FSB. Do this and you can use a standard night sight.


I'll try to remember that, but I don't think I'm ready to spend another $100 on a rifle im kinda irked about just yet. Perhaps later, but thanks again for that info!

Originally Posted By SSeric02:
What is the effect of using an A2 aperture in an A1 sight, BZOing at 36/300 with the small (unmarked aperture) and then flipping it to the 0-2 aperture? Is the 0-2 still effective for 0-200m like it would be on an A2 sighted rifle or carbine?


If you BZO an A1 with an A2 aperture at 36/300 with the small aperture, then it is exactly the same as having an A2 with the sight wheel permanently locked on the 8/3 setting. 0-2 aperture is for 0-200m or any time you need a big hole, and the small one is 300m and out by using a holdover.
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