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Author Topic:   50 yd zero using 25 yd target
Mike_M
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posted 11-28-2003 21:04     Click Here to See the Profile for Mike_M   Click Here to Email Mike_M     Edit/Delete Message   Reply w/Quote
I saw a target especially designed to achieve 50 yd zeros but shooting at only 25 yds. In other words, there was a circle below the point of aim where rounds would strike if rifle zeroed. Anyone got one in pdf format by any chance or know where these are printed or sold? Kinda handy. Saves time.

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It's easier to herd the sheep than to hunt the wolves.

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Tim Burke
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posted 11-29-2003 05:41     Click Here to See the Profile for Tim Burke     Edit/Delete Message   Reply w/Quote
This isn't hard to do, but it is ammo, barrel length and offset sensitive.

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TB., NC

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Keith Neal
Moderator
posted 11-29-2003 05:47     Click Here to See the Profile for Keith Neal   Click Here to Email Keith Neal     Edit/Delete Message   Reply w/Quote
I have not seen one, but suggest it is a gimmick that would be of little use.

First, the 25 yard point of impact would depend on the ballistics of the round and the height of the line of sight above the bore. The target would have to be designed for a specific set of these variables, including barrel length and ammunition.

Second, the 25 yard point of impact is too hard to read to reliably extrapolate to longer ranges, except to get you on the paper at longer range for verification.

Third, the 50 yard zero is usually an intermediate zero. It is the first intersection of the bullet with the line of sight. The bullet then comes back down to line of sight at the true zero range, probably somewhere in the vicinity of 200 yards, depending on the ballistics of the round in a particular rifle. The true zero range must be verified to have a rifle properly sighted in.

I have seen people sight in at 25 yards and be off by feet at the intended zero range.

For a scoped "deer rifle", 1/4" low at 25 will get you in the ballpark for testing at longer range. For a higher line of sight like an AR, 1/2" will get you started.

For a good zero with minimum ammunition expenditure, one round at 25 yards is enough. Adjust sights and repeat to get near the desired point of impact. Then three rounds at fifty, adjust and repeat. At one hundred, three or five round groups centered 2" above point of aim are good for almost any rifle application. Then check and memorize points of impact at 150, 200, 250 and 300. Beyond 300 is just wishing for most folks. If you have been shooting from a bench rest, now go to field positions, where everything will be different, and adjust the zero.

At least that is my approach, and I have been satisfied with the results.

Keith

[This message has been edited by Keith Neal (edited 11-29-2003).]

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Mike_M
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posted 11-29-2003 16:38     Click Here to See the Profile for Mike_M   Click Here to Email Mike_M     Edit/Delete Message   Reply w/Quote
Good info, guys. I should have clarified that this was specifically for the 5.56mm used at an AR15 class. The way the thing worked was we sigted at one point on the target and all rounds struck in circle below (if all went as planned, of course).

I should also add that the target was designed for the round, and that we confirmed Z at 200yds.
Only purpose of post was to shorten the time to zero by shooting first at 25 and then at 200 to obtain the "50 yd" zero that also intersects at 200. Just thought there might be one for sale out there or someone might have rigged up his own and put it on pdf.

Thanks


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It's easier to herd the sheep than to hunt the wolves.

[This message has been edited by Mike_M (edited 11-29-2003).]

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Forest
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posted 11-30-2003 15:26     Click Here to See the Profile for Forest   Click Here to Email Forest     Edit/Delete Message   Reply w/Quote
Mike,
A good rule of thumb is the rounds should strike 1.2" low at 25 yards to get a 50 yard zero for an AR-15 using most any ammunition.

You will need to fire at 200M to 'tweak' the zero - but you should be good enough to 100 yards for a class.

If you are using the A2 type elevation adjustable iron sights you can set them as indicated here: http://groups.msn.com/TheMarylandAR15ShootersSite/25yardzeroingmethod.msnw when sighting in at 25 yards for a 50y/200m zero.

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Pat _Rogers
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posted 11-30-2003 15:41     Click Here to See the Profile for Pat _Rogers   Click Here to Email Pat _Rogers     Edit/Delete Message   Reply w/Quote
Geez Mike, you sholda'asked, and i would have left you some...

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S/F

Pat Sends

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Randy Cain
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posted 11-30-2003 16:37     Click Here to See the Profile for Randy Cain   Click Here to Email Randy Cain     Edit/Delete Message   Reply w/Quote
You could always set up your target right next to you on the firing line, facing downrange. Place a mirror at the 25 yard line facing back at you. Your target would appear to be 50 yards away and you could just reach over and tape your holes without having to get up and walk downrange.

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Randy Cain
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posted 11-30-2003 16:52     Click Here to See the Profile for Randy Cain   Click Here to Email Randy Cain     Edit/Delete Message   Reply w/Quote
PS - Don't hold me responsible if you become subject to 7 years of bad luck!

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David Blinder
Novice
posted 12-01-2003 01:46     Click Here to See the Profile for David Blinder   Click Here to Email David Blinder     Edit/Delete Message   Reply w/Quote
Mike,

Are you talking about the one I provided when Pat was in Atlanta? If so, let me know and I'll be happy to send one.

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Chuck
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posted 12-01-2003 14:08     Click Here to See the Profile for Chuck   Click Here to Email Chuck     Edit/Delete Message   Reply w/Quote
Pat (or anyone else), I'm confused. In the Army we are taught that Point of Aim/Point of Impact is the same for the M-16A2 zero at 25/300 meters. Is the 50/200 meter POA/POI zero simply another technique; i.e. does it zero to different points in the same trajectory as the 25/300 m zero? If that is the case, why is this preferable?

Thanks,

Chuck

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STLRN
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posted 12-01-2003 16:51     Click Here to See the Profile for STLRN     Edit/Delete Message   Reply w/Quote
The Marine Corps originally refused, except for as a no other choice method, to use the 25m zero because the projo doesn't fully stabilize for 27 m.

The last time I looked at the new addition to the A2 user manual for 25m zero it stated to go 3+1 for a 25 meter zero, than reset the sight to 3 for your BZO.

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Mike_M
Member
posted 12-01-2003 21:47     Click Here to See the Profile for Mike_M   Click Here to Email Mike_M     Edit/Delete Message   Reply w/Quote
David-- yep, that was it. Thanks for sending it on by email. I noticed it wasn't copyrighted. Who knows? Maybe after this discussion, it'll become a hot item. You might make a mint on it. Maybe a SWAT tear out item even. It is a good idea, and I appreciate your sharing it.
Pat--I'd figured I could find it for sale on the www. Wrong. Besides, you had me so busy learning and unlearning, that clever little target was the last thing on my mind! I do figure that I'll probably never need it again since the much-despised "tactical Bushnell" will hold that zero 'til Frank Lautenberg and Hillary sign up for one of your courses. Just think how many more federal dollars would be freed up to fund welfare checks if y'all quit wasting money on those expensive Aimpoint thingamajigs. Why, with procurement from Cabelas', you could issue all the troops $90 1.5x--4.5x Bushnells with money left over to fund the prescription drug plan! What a country.
Randy--Funny. Fact is, some weeks, walking back and forth to see where the holes are is the best exercise I get. Probably should just forget the 25-(50)-200 target, zero at 200 and sprint back and forth--with weapon and gear of course.
Chuck and Forest--That Maryland AR15 site link Forest posted has got a lot of good info on it. (Sort of surprising they can still own guns in Maryland.) Chuck, that site explains the advantage of zeroing at 50yds/200yds instead of the military 25m zero (which I think intersects line of sight again at 275m). Flatter trajectory over most frequent combat shooting range, lower apogee, use of yards intead of meters. The target David and Pat brought with them for zeroing at Pat's carbine course in Conyers, GA in October had a small circle just below the target's point of aim. Idea was simple: If zeroed, bullets should strike about inch and a half below point of aim. Then, check it out and make adjustments on 200yd range. Just saved some time and, where the short-range range is less than 50yds long, it let's you put the first zero on the weapon in a limited space. Kinda handy. It made sense to me and, so, another time-honored tradition of conventional wisdom goes by the wayside.
Merry Christmas to all,
Mike

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David Blinder
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posted 12-02-2003 04:00     Click Here to See the Profile for David Blinder   Click Here to Email David Blinder     Edit/Delete Message   Reply w/Quote
Mike,

Actually, based on Pat's advice, I did submit it to the copyright office about two months ago. I don't mind providing it to my students for their personal use and I'm glad you found it useful.

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Chuck
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posted 12-02-2003 14:15     Click Here to See the Profile for Chuck   Click Here to Email Chuck     Edit/Delete Message   Reply w/Quote
STLRN & Mike: Thanks! Leave it to the Army to screw up something simple !

Chuck

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Mike_M
Member
posted 12-02-2003 16:00     Click Here to See the Profile for Mike_M   Click Here to Email Mike_M     Edit/Delete Message   Reply w/Quote
Actually, I see that now. Was just joking before. Good advice. Glad I did not violate your c-right!
Mike

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It's easier to herd the sheep than to hunt the wolves.

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