M-4 50m zero vs. 25m zero

[Pattaya]

This is important. using M885 standard green tip 62gn. ammo in an M-4, the difference in zeroing the rifle at 50m instead of 25m means you can hold center mass out to almost 300m and still expect a hit in the vital area.

Here is the ballistics (bullet path in inches):

Z @ 50m: 25m -1.3", 50m 0.0", 100m +1.7", 150m +1.8", 200m +.2", 250m -3.4"

Z @ 25m: 25m 0.0", 50m +2.7", 100m +7.2", 150m +10.1" 200m +11.3", 250m +10.4"

After retiring in 00' from an ODA, I worked as a Dept. of Energy Firearms instructor for 4 years. When someone explained this to me I wished I had known this when I was on the team. It makes sense. Maybe it will help someone out.

[swatsurgeon]

I'm not an expert on this but have read in 2 or 3 sources that a 50m zero will also zero at 200.....your info at 250 makes sense but 200 does not....unless it is the grain or twist rate....my data was for 55gr with a 1:9
ss

[Pattaya]

Check it out with a ballistics program if you want to. I shot it on a range with both zeros and it's the real deal.

[SERPENT5XX]

I use the 50 M zero on my work amd personal guns. I have found it to be much better than the 25m or standard military zero for shooting from 25-200 meters.
Check out this web site. .

http://groups.msn.com/TheMarylandAR15ShootersSite/zeroingmethods.msnw

It has some graphs which show the fight path of the rounds using different zero methods.

If you guys come up with anything different than what they show please let me know so I can make adjustments.

Thanks!

SERPENT5XX

[NousDefionsDoc]

Most excellent thread!

[agzant]

When my agency started a patrol rifle program, we quickly learned that the 25m zero we were familiar with from the military was not a great plan. We went to the 50m zero for quite a while and found it to be much better. When talking torso shots to 300 it should work great.

Not meaning to hijack the thread, but we have since gone to a 100 yd zero. We looked at this after attending a school with Paul Howe. The premise is that the round is low everywhere except 100. It will be low up close regardless of zero due to sight offset and it's just easier for me to remember that it is always low rather than sometimes low and sometimes high. The listed data is my 16" carbine with 75gr Hornady TAP, but it should close with 62gr and 14.5"barrel.

15 yds -2.5" 50yd -1.5" 75yd -.75" 100yd -0 150yd -1.5" 200yd -3.5"

This works great with an optic like an Aimpoint or EOTech. I always remember to hold high in close and high way out there. Between 50 and 150 just aim dead on even if a head shot is all that's available. At longer ranges it is actually easier for me to hold the dot over the small targets than it is to cover up the target with the dot. This eliminates fooling with the brightness setting when bullets are flying. It also works okay with the ACOGs. When using iron you probably need to adjust the rear sight for range because it's hard to hit a small head and/or upper torso with that big front sight covering it up. If I am anticipating longer shots I might run the rear sight up a few clicks.

I have found both 50 and 100 zeros to be much superior to the 25m/300m one. I don't shoot out that far very often, and if I am then I don't mind adjusting to hit them out there. It's easier for me to think about shooting at a target out there than it is to adjust aim 7" at 100 yds with the 25m zero when I'm excited.

I haven't been on the Maryland AR15 site in a few years, but found it very informative reference the 50 m zero and other battle site zeroing techniques.

Take care
Allen

edit for: malfunction on the data entry due to computer illiteracy.

[NousDefionsDoc]

Good gouge agzant, Anybody seen the average engagement distance for Iraq say, among PMCs? I know, I know, it varies greatly.

I will try both 50 and 100 next week. Thanks for the tips fellows.

[Sionnach]

NDD,

Any info you can share with us on the 50 M vs. 100 M zero?

[stanley_white]

This is important. using M885 standard green tip 62gn. ammo in an M-4, the difference in zeroing the rifle at 50m instead of 25m means you can hold center mass out to almost 300m and still expect a hit in the vital area.

Here is the ballistics (bullet path in inches):

Z @ 50m: 25m -1.3", 50m 0.0", 100m +1.7", 150m +1.8", 200m +.2", 250m -3.4"

Z @ 25m: 25m 0.0", 50m +2.7", 100m +7.2", 150m +10.1" 200m +11.3", 250m +10.4"

After retiring in 00' from an ODA, I worked as a Dept. of Energy Firearms instructor for 4 years. When someone explained this to me I wished I had known this when I was on the team. It makes sense. Maybe it will help someone out.

Do these figures work for a 10.5" barreled M4 as well?

[The Reaper]

Do these figures work for a 10.5" barreled M4 as well?

With a muzzle velocity as much as 200 fps less, I think not, unless you can repeal the laws of physics.

TR

[NousDefionsDoc]

NDD,

Any info you can share with us on the 50 M vs. 100 M zero?
I had it zeroed at 100 for quite a while. I changed it back to 25 to test a new target. Works fine, but I suggest you shoot at whatever distances you need to and actually check where you are impacting.

I wasn't particularly attracted to the idea of a 50M zero.

[stanley_white]

With a muzzle velocity as much as 200 fps less, I think not, unless you can repeal the laws of physics.

TR

Roger. Thank you.

Does anyone have the figures for a 10.5" barrel M4 handy?

[Sionnach]

I had it zeroed at 100 for quite a while. I changed it back to 25 to test a new target. Works fine, but I suggest you shoot at whatever distances you need to and actually check where you are impacting.

I wasn't particularly attracted to the idea of a 50M zero.

Thanks, NDD.

[The Reaper]

At the risk of thinking too far outside the box, I have been experimenting with a 25m. zero on my red dot sights (EOTech 552 and 553), and a 100m. zero on my iron sights (Troy), which I usually leave in the up position anyway.

As long as you remember to transition for the long shots, which I am trying to train into, it should not be a problem.

At a closer range snap encounter, you are going to shoot the red dot anyway, and at the longer ranges, you are taking the time to aim more carefully.

Just an experiement, not advocating this for everyone.

TR

[NousDefionsDoc]

TR,
I have done that as well and really like it.

[Gene Econ]

Guys:

Pole vaulting over mouse turds a bit.

One of my guys took my neat little target I shot showing trajectory given a 300yard zero so he could show his Joes but when the weather breaks some, I will shoot another one and photograph it. I will say this much with any modern certerfire cartridge today -- your ordinate will be between five and eight inches for a 300 zero.

I honestly don't get real hung up over this type of thing. If anyone is so interested in finding out a precise close range zero my advice is to zero your rifle up at the range you want to shoot -- 100, 200, 300 -- could even be 500yards or meters. When you have a good zero at what ever range you want your battlesight zero, draw a round black dot about two inches in diameter on a piece of paper and put that target at what ever you desire for a short range. Then shoot a group and measure the distance between the group and the middle of the dot. The closer the target, the more anal you absolutely must be in your measurements. Remember that ther are four minutes to an inch at 25 meters so you must be anal in your measurement. Also, I do not trust any ballistic program to give me a close, close range zero. They are not refined enough to give you a good close range zero.

I once had some Hooaas make their own 'Thermometer' targets for their individual M-24 and SR-25 rifles. After a number of days on a KD range I decided they were consistent enough in their zeros to have them make their own Thermometer targets and that is what we did using 25 yards as a short range. I had them shoot a 100, 300, 500, 600, and 800 elevation to mark the thermometer targets for the short range zeros. I took the targets home and measured the heights of each group using a micrometer to be as perfect as possible. Then I used my computer to make each of the Hooaa snipers a thermometer target representing his individual M-24 and SR-25. There were differences between rifles and shooters. I have the averages somewhere

If you go through this process to make your own thermometer target, and want to use the same target for a close range zero, ensure you use a plum of some sort when you staple it to a target frame. The vertical line must be verticle as you are not only adjusting for elevation but windage as well. The target must be straight up and down. And, you can not compromise over your zero. It must be absolutely perfect in terms of hitting its respective range index. The biggest problem with these reduced targets is that most shooters have not trained their eyes to see what is and what isn't perfect. So they accept groups that are slightly off and that equates to big time errors at longer ranges.

Enough targetology for one day I think.

Gene

[jatx]

Roger. Thank you.

Does anyone have the figures for a 10.5" barrel M4 handy?

Stan,

There is a lot of variation in muzzle velocity between commercially available loads when the barrel gets that short, so you will need to chrono whatever you're shooting and then use a good ballistics calculator to estimate drop. IIRC, the difference between Hornady's 69 gr. TAP loads is about 200 fps for SAAMI spec vs. NATO spec, for example. Or, if you're just shooting M855, you could search barf.com and someone might already have posted the answer. Or, you could get to a good KD range like Gene said and let us know how the lollipop technique works for you. :cool:

[x SF med]

Guys:

Pole vaulting over mouse turds a bit.

I honestly don't get real hung up over this type of thing. ... the more anal you absolutely must be in your measurements. ... so you must be anal in your measurement. ... you can not compromise over your zero. It must be absolutely perfect in terms of hitting its respective range index. The biggest problem with these reduced targets is that most shooters have not trained their eyes to see what is and what isn't perfect.

Gene


Gene- I will need to go out and have you train me back up, long time off the range for me, but an impending move will put me close, and an FN Para will be finding it's way into my grubby little paws.

You aren't anal about perfection in zeroing, are you? :D

[Sionnach]

TR/NDD: Seems like a most excellent technique.

Gene: I've never heard of a thermometer target. My google-fu is weak, and I didn't see it in FM 23-10. Is this technique specific to the mildot scopes?

I'm still learning to "Train the eyes to see and the finger to move."

You gentlemen are an encyclopedia of knowledge.

[NousDefionsDoc]

LOL - you actually googled "thermometer target"?

If you look at his post, he explained exactly how to do it. He is talking about sniper rifles, but I've done the same thing with M4 (feel free to jump in BasicLoad - I stole it from you). I just wasn't anal about the measurements. LOL

[stanley_white]

Stan,

There is a lot of variation in muzzle velocity between commercially available loads when the barrel gets that short, so you will need to chrono whatever you're shooting and then use a good ballistics calculator to estimate drop. IIRC, the difference between Hornady's 69 gr. TAP loads is about 200 fps for SAAMI spec vs. NATO spec, for example. Or, if you're just shooting M855, you could search barf.com and someone might already have posted the answer. Or, you could get to a good KD range like Gene said and let us know how the lollipop technique works for you. :cool:

Thanks jatx!

I don't know when the next time we're going to the range but I'll experiment and let you all know what I come up with.

FYI - We're using M855.

[Gene Econ]

Gene: I've never heard of a thermometer target. My google-fu is weak, and I didn't see it in FM 23-10. Is this technique specific to the mildot scopes? I'm still learning to "Train the eyes to see and the finger to move."

Sionnach:

Why would this technique be specific to a mildot scope?

Does the target know or care about what type of sight you are using?

I have used this type of target for any type of sight. If you go with irons, your aiming point needs to be big enough to see is all.

It is of no value under 300; is of almost no value at 500; and is of 'ball park' value if you intend on shooting regularly at ranges past 500. It is better than no zero but isn't perfect.

Gene

[Gene Econ]

Gene- I will need to go out and have you train me back up, long time off the range for me, but an impending move will put me close, and an FN Para will be finding it's way into my grubby little paws. You aren't anal about perfection in zeroing, are you? :D

An FN Para? We can certainly blast away with that! Honestly, you would be surprised at what one can do with a military issue blaster.

I can get pretty anal about zeroing but I take things with a grain of salt. Rarely does one's zero hold perfectly hour to hour, let alone day to day or week to week. Position changes, light conditions, air temperature effects on the rifle and ammo, fatigue which effects the physiological workings of the body -- all come into play day to day, hour to hour, second by second etc. The trick is to know by your calls when something is going on and adjust the sights as needed.

That is why I believe muscle memory is a flawed concept in terms of a training foundation. How can a guy's muscles memorize something that changes by the second?

Gene

[Peregrino]

My turn to make a minor addition to the discussion. Gene hit the nail on the head with "pole vaulting mouse turds". Have realistic expectations and work towards achievable goals.

FWIW I train to two standards; hasty and deliberate. Hasty means hitting a rectangle 9" wide x 18" tall out to the weapon's max effective range as quickly as accuracy permits. At short ranges (< 250 M) that's a pretty generous standard and relatively easy with any of the listed zeros. PBR more than meets my requirements without meticulous measurements/calculations. Deliberate requires sub-MOA accuracy. Not as easy/fast but acheivable with practice. At longer ranges it's impossible without precision marksmanship skills.

An intimate knowledge of your weapons system and its ammo is critical. Especially since at longer ranges everything requires an adjustment for elevation. I'm amazed this thread hasn't mentioned range estimation yet. Personally I think it's more important than anything covered so far in the ballistics discussion (military quality ammo has relatively uniform, well known ballistics).

Most of my shooting now is KD for NRA Service Rifle. My match rifles are zeroed (iron sights) at 200 yds and I use "comeups" (more zeros) for 300, 500, and 600 yds. Gene's "thermometer" effect is readily visible when I forget to crank the sights down from one match to the next. Thankfully it only takes one round to realize the goof and sighters aren't part of the score. For convenience my carbines are zeroed at 100 yds which is fortuitous for the ACOG (TA31F) because it matches the BDC reticle.

This thread has reawakened my interest in optimizing trajectory/determining PBR. I will be chronying a new load shortly and will adjust the carbines to compensate. The wife's probably going to protest the range time (not really) but it'll be fun. My .02 - Peregrino

[jatx]

I'm amazed this thread hasn't mentioned range estimation yet. Personally I think it's more important than anything covered so far in the ballistics discussion (military quality ammo has relatively uniform, well known ballistics).

Sounds like a great thread, sir. :munchin

FYI - We're using M855.

M855 only clocks about 2640 fps out of a 10.5" barrel, well below the velocity required for full fragmentation of the round. I don't know what your uses will be, but you might consider using a heavier commercial HP or a specialty round if they are available to you.

[frostfire]

don't want to start a new thread on this.

Paul Howe on battlefield zero, iron vs. optics, etc..
Excellent no-nonsense approach and the practical visuals makes grasping the concept instantaneous.

http://www.combatshootingandtactics.com/published/The%20Battlefield%20Zero%20Full%20Pictures.pdf

[Blitzzz (RIP)]

I,m not sure I understanding the "why" a 25 meter or 50 meter zero unless your just talking iron sights.

A good point for range estimating is to "think" in shooting increments, ie. 50 meters or 100 meters and combining that with your known ballistic curve. It may sound confusing but it's a system I have used for well over 30 years with M118 ball. By thinking in increments I'm able to quickly Hold off from my zero to make the hit. I found this really works well with Mil Dot.
I,m not trying to create confusion, sorry if I did.

This was in response to the question of 10.5 in barrel zero thread.
I wrote the following:

I agree with 100 meters.
if you zero at 100 meters then the following:

M-193 ball = 4 inch target area out to 150 meters.

M-855 ball =4.2 inch target area out to 150 meters.

Added Info:
also if you zero the M193 ball @ 250ms you have +9.9 inch at 200ms, -15.1 at 300.

and for the M855 ball with 300 meter zero, = a +12.6 inches @ 150+
I'd do the 100 meter zero
Blitz

But in response to your question ,Yes, 200 meters would be much like a "point blank zero". Used in hunting circles it refers to the zero distance that allows the shooter to engage a "target" with out hold off. If you can achieve that with a 200 meter zero then do it. but as you stated that's a 12 inch circle at 300 meters.
You might tighten that circle at about 175 meters to around 9.5 inches.

Let us know when you do, good luck Blitz

[Sinister]

Reinforcing Gene's point, the reason this comes up again and again is because folks either don't have real field fire or KD ranges to no-shit confirm their zeroes or they've never done it.

More a point of "Don't know" and "Never done it."

It seems the majority of shooters train and practice between 25 and 100 meters and never seriously shoot at anything past 200 -- ever. There are the occasional trips to the qualification range to shoot pop-ups, where a hit to an E-type (anywhere) drops it -- and the shooter doesn't know if he hit center, a wrist, the top of the shoulder, or base of the scalp.

A GI 25 Meter zero will put most shots in the upper 1/3 of a 300 Meter E-type. Given the dimensions of the head a slight breeze will blow many shots off-target.

A 50-Meter zero will give you more of a centered, center-of-mass grouping at 300. If you think of Center-of-Mass as truly the center of an E-type (minus the head) you reduce the risk of losing any over the tops of the shoulders in any kind of breeze.

20 years ago at Range 37 all students zeroed at 100. This worked for the majority of shots since everything for 6 weeks was closer than that.

Unfortunately Musketry practice in both SOF and the GP Forces now seems to concentrate at much closer than 50 Meters. Farther seems the realm of folklore or "Don't know how to train it" unless it's on the pop-up range.

Thermometer targets like Gene described work for rough zeroes all the way to 1,000 if you know your come-ups. If you don't have proper paper thermometer targets you can improvise by taking an E-type, turning it upside down, and gluing something like a round Shoot-and-See target where the face would be.

Using your elevation drum or the range markings on your irons, Aimpoint, or ACOG you start by placing bullets at Center-of-Mass of the bull for 100. Come up to your 200 and 300 settings and you'll see your groups go up the thermometer stalk. With an ACOG you can go all the way up your markings (I think to 800).

This is the same method the Marines use for confirming sniper scopes on helo deck 25-Meter ranges. At 25 Meters set your scope for 300 and your groups should be 5/8ths-inch high (using an M40A1 and the older Unertl or something like an M3LR).