View Full Version : 25yd Zero VS 50yd Zero
Spent this last Sunday on my range measuring out exact distances for testing and zeroing purposes. When I got done, I thought it would be nice to show people what a 25yd zero vs a 50yd zero looked like at 25, 50 and 200yds. I also wanted to use two entirely different rounds to see if there was much difference at distance.
The weapon that was used was a Charles Daly LE M4 that is on loan to me for T&E. The weapon was zero'd with Remington 55gr. I also used BH's 77gr MK's for the shoot. The groups were shot from the prone position with a magnified optic.
DISCLAIMER: This is not a formal ballistic test or evaluation. The sole purpose was to have a little fun and hopefully show people what a 25yd zero looks like on paper vs a 50yd zero. For a true accuracy test, I much prefer to use 5rd groups (minimum) or 10rd groups (preferred). So take what you want from this discussion.
There are some interesting things about my little test. First, the group sizes at 200yds were VERY tight (around 1MOA) with the 25yd zero and nearly triple with a 50yd zero. Why this is, I have no idea. :confused:
The second interesting thing is that with a 50yd zero, the 55gr ammo was 1.5" low at 200yds. The 77gr was at least 4" low at 200yds. This was surprising to me as I would have said that the 77gr would have been much closer to point of aim at 200yds.
Hopefully this will help some of you to better understand point of impact at various distances and understand what your offset or hold over needs to be at different distances.
C4
http://www.gandrtactical.com/images/archive/CD/groups%20shot%2025yd%20zero.jpg
http://www.gandrtactical.com/images/archive/CD/Groups%20shot%2050yd%20zero.jpg
RogerinTPA
04-28-08, 18:22
I guess the old adage of a 50 yard zero only applies to the 55 grain bullets. That looks spot on. I am surprised to find the heavier bullets impacting so low at 200 yards with 50 yard zero and way high with the 25. I wonder if you zeroed both at 200yards, would the impact be the same or higher at 25 or 50 yards... I'll have to try that with 55 grain vs 62. Good shooting by the way!
Interetsing stuff.
Did you have a chronograph? Bipod? Sling?
Do you recall the order in which you shot these rounds? When you start mixing powders, it can take a while for shots to settle in.
BTW, your load must have been smoking -- using this ballistics calculator (http://www.eskimo.com/~jbm/calculations/traj/traj.html), and a 2.6" sight height (guesstimate), that 77 grain load had to be clocking 2925 fps at the muzzle to end up 10" high at 200.:eek:
Not bad for a M4. ;)
Interetsing stuff.
Did you have a chronograph? Bipod? Sling?
Do you recall the order in which you shot these rounds? When you start mixing powders, it can take a while for shots to settle in.
BTW, your load must have been smoking -- using this ballistics calculator (http://www.eskimo.com/~jbm/calculations/traj/traj.html), and a 2.6" sight height (guesstimate), that 77 grain load had to be clocking 2925 fps at the muzzle to end up 10" high at 200.:eek:
Not bad for a M4. ;)
No chrono, sling or bipod. Just shooting prone (which is how real men do it). ;)
Yes, I do remember the order. The 55gr was always shot first and then the 77gr.
I have some MK262 MOD 1 coming in soon, and I intend to shoot some groups with that VS .223 77gr and see what the differences are at distance.
C4
50 yard zero is rough. You should use the 50 yard zero to get "on paper", then move out to 200 to fine tune, then back in to 50 to reconfirm. Quite often when you first get to 200 you'll find that you're not as "on" as the theory would dictate that you should be. Once you zero at 200, however, and move back in to 50 you'll find that you're very nearly spot on.
This is done at every single Randy Cain carbine class that I'm aware of. It takes at least half of TD1 in a 3-day class, but it is well worth it. Randy believes strongly that one of the things you should leave the class with is a good, strong, known, zero. I appreciate this as I don't have ready access to a 200 yard range for this type of thing.
No chrono, sling or bipod. Just shooting prone (which is how real men do it). ;)
Exactly. There's no tables, benches, rests, and bean bags in a gun fight. So why zero that way? :p
50 yard zero is rough. You should use the 50 yard zero to get "on paper", then move out to 200 to fine tune, then back in to 50 to reconfirm. Quite often when you first get to 200 you'll find that you're not as "on" as the theory would dictate that you should be. Once you zero at 200, however, and move back in to 50 you'll find that you're very nearly spot on.
This is done at every single Randy Cain carbine class that I'm aware of. It takes at least half of TD1 in a 3-day class, but it is well worth it. Randy believes strongly that one of the things you should leave the class with is a good, strong, known, zero. I appreciate this as I don't have ready access to a 200 yard range for this type of thing.
I agree. On my normal training weapon, I zero at 50 and then shoot at 200yds to see where I am at.
C4
Exactly. There's no tables, benches, rests, and bean bags in a gun fight. So why zero that way? :p
LOL, very true. JMART was just trying to get exact data and this was just something fun I was messing with on a lazy Sunday afternoon.
C4
Thanks for the testing and then posting of results.
Keith
Failure2Stop
04-30-08, 06:55
50 yard zero is rough. You should use the 50 yard zero to get "on paper", then move out to 200 to fine tune, then back in to 50 to reconfirm. Quite often when you first get to 200 you'll find that you're not as "on" as the theory would dictate that you should be. Once you zero at 200, however, and move back in to 50 you'll find that you're very nearly spot on.
Thank goodness I am not the only one insisting on this zeroing method!
I thought I was losing my mind after a discussion a couple of years ago on TOS. (ETA- I guess we all have similar experiences ;))
I put a lot of weight in correctly zeroing.
DavidFourteen
04-30-08, 09:13
Thanks!
I have read many pages on the merits of the 50yd zero on another site, but the impression I got was that the posters believed that the 50yd setting was the same as the 200yd setting, with all ammunition types -- which it obviously is not.
16" barrel
www.box.net/shared/static/k1v7or2g4k.jpg
20" barrel
www.box.net/shared/static/wy10zgtck8.jpg
I thought I was losing my mind after a discussion a couple of years ago on TOS.
Not a subject to discuss on TOS for sure!
After the last class I took, I'm convinced that the average AR owners don't have a solid grasp of marksmanship or a good zero. It was a carbine class with all shooting inside of 100 yards, and all targets were checked after each drill both days.
It seemed to be just like most of the bean classes I've taken before. People with neat stuff on their guns, but they can't get a decent group. The AR is an accurate enough gun that you can get away with a bad set up and still trick yourself into thinking you have a good zero or know your POI.
The groups I shot were not that impressive, and were what I'd consider average at best overall. But I outshot everyone in the class with my old beater SBR.
Thanks!
I have read many pages on the merits of the 50yd zero on another site, but the impression I got was that the posters believed that the 50yd setting was the same as the 200yd setting, with all ammunition types -- which it obviously is not.
Depending on how tight your zero is at 50yds, you can be pretty close, but it is always a good idea to confirm your POI at 200yds.
C4
Not a subject to discuss on TOS for sure!
After the last class I took, I'm convinced that the average AR owners don't have a solid grasp of marksmanship or a good zero. It was a carbine class with all shooting inside of 100 yards, and all targets were checked after each drill both days.
It seemed to be just like most of the bean classes I've taken before. People with neat stuff on their guns, but they can't get a decent group. The AR is an accurate enough gun that you can get away with a bad set up and still trick yourself into thinking you have a good zero or know your POI.
The groups I shot were not that impressive, and were what I'd consider average at best overall. But I outshot everyone in the class with my old beater SBR.
Right you are. My favorite is watching folks make head shots at 10-15yds and seeing everything 1.5"-2" low and cannot figure out why. :confused:
I generally win competitions in classes with a 4MOA Aimpoint and 10.5 (competing against variable powered optics and ACOG's). This should never happen.
C4
Robb Jensen
04-30-08, 11:38
Right you are. My favorite is watching folks make head shots at 10-15yds and seeing everything 1.5"-2" low and cannot figure out why. :confused:
I generally win competitions in classes with a 4MOA Aimpoint and 10.5 (competing against variable powered optics and ACOG's). This should never happen.
C4
Yeah you and I with our 10" SBRs with Aimpoint T1s were kicking ass on the 'walk backs'. :D
50 yard zero is rough. You should use the 50 yard zero to get "on paper", then move out to 200 to fine tune, then back in to 50 to reconfirm.
And if you find you are off at then off at 50, what do you do? Adjust to get zeroed at 50 again, or do you keep the 200 yd zero and just make a mental note of where you are at 50?
Wayne Dobbs
04-30-08, 14:19
jmart,
You won't make that big a correction unless something is terribly wrong with your hardware or even more likely, with your software. Remember that the purpose of the 50 yard zero is to get you close at 200 (which has been reinforced above). Get the 50 yard zero done fairly well and then refine the 200 to a "dead nuts" standard. Then shoot it at 50 and 100 and note what's happening. I guarantee that you won't be able to hold within the variation distance that may come up at 50 and for dang sure not at 200 in FIELD positions.
I pretty much agree with everything you're saying. It's just the idea about getting "gross" zero initially, move out to 200 and "fine tune", then check back at 50. Well if you are off again at 50, what to do? Just make a mental note or readjust? You can't have both.
I'm more inclined to get a good zero at 50 and then just shoot at other ranges and see what it's doing. Hell, in a field situation, I doubt you are going to be able to determine whether you are at 175, or 200 or 225 unless you have ranging capability in your optic. Let alone hold tight enough for the distance.
And I tend to believe, at least for my purposes, I live in a 0-to-100 world.
And if you find you are off at then off at 50, what do you do? Adjust to get zeroed at 50 again, or do you keep the 200 yd zero and just make a mental note of where you are at 50?
I've never seen anyone be off more than an inch or so at 50 after correcting at 200.
I've never seen anyone be off more than an inch or so at 50 after correcting at 200.
Gotcha.
Just out of curiosity, when you establish your initial 50 yd zero, how far off at 200 are you before you fine tune? More than an inch or two?
I've got to admit, my time shooting at 200 and beyond is very limited. Most of the time I'm working between 25 and 50.
I pretty much agree with everything you're saying. It's just the idea about getting "gross" zero initially, move out to 200 and "fine tune", then check back at 50. Well if you are off again at 50, what to do? Just make a mental note or readjust? You can't have both.
I'm more inclined to get a good zero at 50 and then just shoot at other ranges and see what it's doing. Hell, in a field situation, I doubt you are going to be able to determine whether you are at 175, or 200 or 225 unless you have ranging capability in your optic. Let alone hold tight enough for the distance.
And I tend to believe, at least for my purposes, I live in a 0-to-100 world.
If you look at the shots I made at 50yds (on the 50yd zero target), they were low. Those black dots on there were 1MOA. So if I went to the top of them, I would get a little closer to hitting the POI at 200yds.
So yes, you could fine tune a little more if you so chose and it would not hurt your 50yd zero.
C4
Gotcha.
Just out of curiosity, when you establish your initial 50 yd zero, how far off at 200 are you before you fine tune? More than an inch or two?
I've got to admit, my time shooting at 200 and beyond is very limited. Most of the time I'm working between 25 and 50.
I think as a Civy, you are never going to be taking 200yd shots (in defense of yourself), but you just never know and it is a good idea to understand what your AR is doing at those distances.
C4
Gotcha.
Just out of curiosity, when you establish your initial 50 yd zero, how far off at 200 are you before you fine tune? More than an inch or two?
I've got to admit, my time shooting at 200 and beyond is very limited. Most of the time I'm working between 25 and 50.
Well, for me the "group" at 200 is more like a "pattern". :D
I like to fire at least 20 rounds at 200 to get an idea of the center of the "pattern" and throw out any obvious fliers. Because my groups aren't always as tight as I'd like I don't have a specific "off by 2 inches" answer I can give.
Remember that the purpose of the 50/200 zero is so that you will always be within 2-2.5" from contact out to 200+ yards. If you're not getting the 50/200 cross then who knows where you are at 100. I guess you could check, but if you're 1" high at 50 and 2" high at 200 you may well be 5" or more high at 100, making the whole excercise somewhat pointless.
This really is one of the unsung values of a class like Randy's. I'll probably take another one of his carbine classes early next year JUST to get a zero on a couple of different carbines. :D
50 yard zero is rough. You should use the 50 yard zero to get "on paper", then move out to 200 to fine tune, then back in to 50 to reconfirm. Quite often when you first get to 200 you'll find that you're not as "on" as the theory would dictate that you should be. Once you zero at 200, however, and move back in to 50 you'll find that you're very nearly spot on.
This is done at every single Randy Cain carbine class that I'm aware of. It takes at least half of TD1 in a 3-day class, but it is well worth it. Randy believes strongly that one of the things you should leave the class with is a good, strong, known, zero. I appreciate this as I don't have ready access to a 200 yard range for this type of thing.
I thought the 50yrd IBZO was ment for 200meters and not 200yards. This would explain why its off.
I thought the 50yrd IBZO was ment for 200meters and not 200yards. This would explain why its off.
You are correct that a 50yd zero would re-zero around 200M (218yds). The problem is that it really depends on the barrel length and ammo used. As you see in my pics, the 55gr ammo is only 1.5" low from the 200yd point of aim.
What was interesting is that the 77gr followed the 50yd/200M rule, but the 55gr did not.
I also have another theory about 25yd zero and its down range accuracy capability, but will hold off on it until I get to test it out.
C4
Wayne Dobbs
04-30-08, 18:38
Grant,
200 meters is 218.7 yards, not 182. I always take meters and add 10% for a quick and dirty estimate of how many yards a distance is.
jmart,
Don't wrap around the axle about 50 yard error vs a refined 200 yard zero. Remember that we're dealing with geometry here and a small change up close (50) will equate to a large change at a distance (200) and vice versa. If you make a four inch change at 200 yards, it will only affect your 50 yard point of impact a whole inch. And, like I said before, you're most likely completely incapable of holding inside that "error area" at any distance of consequence (unless you're not human).
Wayne
jmart,
Don't wrap around the axle about 50 yard error vs a refined 200 yard zero. Remember that we're dealing with geometry here and a small change up close (50) will equate to a large change at a distance (200) and vice versa. If you make a four inch change at 200 yards, it will only affect your 50 yard point of impact a whole inch. And, like I said before, you're most likely completely incapable of holding inside that "error area" at any distance of consequence (unless you're not human).
Wayne
Got it (although not quite sure I was wrapped around axle. Do a search for other posts from me and you'll get a much better sense of the jmart "wrappage" index. This one rated maybe a 2.3;). Hardly one of my best efforts:p )
John Hearne
04-30-08, 19:51
I thought the point of a 50 yard zero was to have an easily obtainable zero that worked out to reasonable distances. I've been told that a 50 yard zero will be within 6" out to 250 yards. Nothing I've seen in these posts seems to indicate otherwise unless you have hardware issues.
I sight in dead on at 8/3 at 34 yards. This will give a 300m zero at 8/3 according to my ballistics charts. Then I move it down to 8/3-2 clicks and wherever that is SHOULD be IBZ. I fired a group at 100m and it was 2.25" high. The alternative would be 1.25" high if I moved the sight-post down one click. (it is 1 MOA clicks IIRC, no?). Either way, 1.6" is what it SHOULD have been. Good enough for me! (this is iron sights afterall!, the group was a 5-shot with M855 measuring 2.25".)
Grant,
200 meters is 218.7 yards, not 182. I always take meters and add 10% for a quick and dirty estimate of how many yards a distance is.
jmart,
Don't wrap around the axle about 50 yard error vs a refined 200 yard zero. Remember that we're dealing with geometry here and a small change up close (50) will equate to a large change at a distance (200) and vice versa. If you make a four inch change at 200 yards, it will only affect your 50 yard point of impact a whole inch. And, like I said before, you're most likely completely incapable of holding inside that "error area" at any distance of consequence (unless you're not human).
Wayne
You are correct. I for some reason was doing yards to meters and should have been doing meters to yards. That is what I get for not paying attention. :D
C4
I thought the point of a 50 yard zero was to have an easily obtainable zero that worked out to reasonable distances. I've been told that a 50 yard zero will be within 6" out to 250 yards. Nothing I've seen in these posts seems to indicate otherwise unless you have hardware issues.
The common logic is that a 50yd zero will give you a 200M repeat zero. This is a desirable zero because you are getting towards the end of hte 5.56's capability. What we are finding interesting is that the shots I took at 200yds (182M) were all really low (especially the 77gr).
C4
03humpalot
05-01-08, 10:39
WS6,
you mentioned 8/3, are you shooting a 20 inch rifle? A2/or A4 style?
If so its 1 1/4 MOA per click on the front sight post IIRC.
Speaking of which anyone know the MOA value per click of the M4 front sight post? I seem to have forgotten.
Wayne Dobbs
05-01-08, 12:43
A2 Front Sight
Range in Yards 25 50 75 100 200 300
1 Click in Inches 11/32 11/16 1 1/32 1 3/8 2 3/4 4 1/8
Clicks to get 1" 2.9 1.5 1.0 0.7 0.4 0.2
Notes For M4 (Approx.), Approx 1" Low at 25Y for 200Y BZO (BH 68gr), (AE55=1.3")
Grant,
It might be interesting what you find trajectory wise when comparing the 55, 62 and 77 out past 200M...say 300/400/500...etc.
Think the 77's may retain velocity better at the extended ranges as the 55's drop off?
RogerinTPA
05-01-08, 20:49
Getting a good idea of your zero at 50 yards makes a lot of sense. Optics dependent you may want a 100 meter zero or a 200 yard. Most people don't take into account the sight height, muzzle velocity/bullet weight (from a shorter vs. longer barrel), and zero requirements for a bullet drop compensator in optics.
I chrono my rifles, with my ammo, in my area, I usually set up my ARs to hit 1.5" low at 25 yards.
5.56
Due to my optic 2.9" height with BDC needs a 200yd zero
14.5" 55gr 50yd 0.5" low gives 200yard ZERO
16" 55gr 50yd 0.5" low gives 200yard ZERO (only about 3" less drop out to 800yards than the same round from a 14.5")
14.5" 62gr 50yd 0.3" low gives 200yard ZERO
16" 62gr 50yd 0.4" low gives 200yard ZERO (Only about 6" less drop out to 800yards than the same round from a 14.5")
7.62
16" barrel has 2.9" high optic that needs a 200YARD zero
150gr 50yard 0.1" high gives a 200 yard zero (MV 2540)
20" barrel has a 1.75" high optic that needs a 100METER zero for BDC
150gr 50meter ZERO gives 100 METER ZERO (MV 2660)
So with an AR I shoot a nice accurate group at 25yards 1.5" low or 50yards 0.5" low and then "fine tune" it at the 200 yard or 100 meter line.... then confirm your BDC works by shooting at 400, 500, 600, 700 yards.
These great groups were shot, by a very goof friend, with a 16" AR, a 200yard Zero and 62gr loads...
400 yards
http://i275.photobucket.com/albums/jj290/c2008pictures/G%20Stuff/USE/400yardscoldbore01.jpg
500 yards (taping the targets, we were shooting from the line of trees in the center of the picture)
http://i275.photobucket.com/albums/jj290/c2008pictures/G%20Stuff/USE/08260704.jpg
600 & 700 yards
http://i275.photobucket.com/albums/jj290/c2008pictures/G%20Stuff/USE/082607600700.jpg
Cameron
Thats great gouge and very good marksmanship. Was it a powered scope or red dot optic used?
Failure2Stop
05-02-08, 06:11
Just another 2c, since this thread has taken a turn.
A rifle can only be considered to be zeroed for a given distance when fired at that distance. (True Zero- Achieving point of impact (POI) at the point of aim (POA) at a given distance)
i.e.- a 36 yard POA/POI group is NEITHER a 300 yard zero or a BZO. It is a 36 yard zero, which should give approximately COM hits at 300 yards with no weather effect. Key word are "should" and "approximately".
I have shot a lot of 36 yd, 25 m, and 50 m/yard zeroes. Most of them were not True Zero correct at their supposed trajectory match. The intent of the 25/36 were not as end-states, but simply to expedite the actual zeroing process. Any field expedient method (25m, 36 yd) should be confirmed at actual distance, and though a 50m/yd zero is very workable, it is not a true 200m/yd zero.
I zero all my irons at 50y. It's a great zero for the ranges around where I am. I do Zero the ACOG at 100m and IOR at 100m. I need to look into the 50m with my Aimpoint(on Arsenal AK) and EoTech(on Steyr/Saber A3).
Where would we be at 300y? Pretty low I'm guessing?
This is great stuff- thanks, very helpful- CB
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