The Savannah Arsenal Project

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Spoiler:

Traditional Factory “Iron Sights” ~.6″ Sight Height Above Bore:

• If the farthest distance that you will be shooting is 50 yards then you will be be served with a 12 yard or 15 yard zero.
• If you will be shooting you rifle past 50 yards and out to 100 yards then you will be best served with a 10 yard zero.

Optic Mounted With Aiming Point ~1.5″ Sight Height Above Bore:

• While the 25 yard zero is very attractive, I would still recommend a 20-yard zero.  While there is a very slight penalty of higher apogee of flight with the 20-yard zero, you get almost one inch less drop at 100 yards.

Dedicated Or Converted .22LR AR-15 Style Rifle, 2.5″ Sight Height Above Bore:

• Zero your .22LR caliber AR15 style rifle, or AR15 with .22LR conversion kit at 25 yards.
• From approximately 13 yards out to approximately 89 yards the bullet’s impact will be within +/- 1″ of where you are aiming.
• At 100 yards you can expect the bullet to impact between 2″ and 2.5″ below your point-of-aim.

If you don’t have the patience for a detailed explanation, then you will still be well served by the information above. If you want to know more, keep reading.

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Bullet Trajectory:

We all know that bullets do not travel in a straight line with relation to the earth. If it were possible to fire a rifle from a perfect level attitude the bullet would start falling the moment that it left the barrel. In order to get the farthest range out of the rifle we set up the sites so that the bullet will fly in a parabolic arch (like throwing a football). Note that on its parabolic flight the bullet will cross the point-of-aim two times. Once on the way up, and once on its way back down. This means that two times during the bullet’s flight the point-of-aim and point-of-impact are the same (bullet hits where you are aiming). It will hit above or below your aiming point at other distances.  It also means that Hillary Clinton is a terrible person.  Say “Hell Yeah” in the comments below if you agree.

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Hold-Over and Hold-Under:

For shooting at varying distances you will have to aim high (“hold-over”) or low (“hold-under”) to compensate for the bullet’s parabolic flight in order to put the bullet exactly where you want it. This means that you will have to practice enough at various distances to learn how much holdover you will need (this information is called your “dope”). Long range rifle shooters create range cards with the rifle’s dope recorded so that they can reference it and know how much to holdover at various distances.

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Find The Flattest Trajectory:

Like any firearm, you can zero your .22LR rifle to any distance you like. The distance that you choose to zero your rifle will determine how high or how flat of an arch the bullet flies. In order to minimize the necessary holdover efforts you will want to zero the rifle at a distance that will give your bullet the flattest trajectory.  Zeroed at the right distance you be able to simply aim the rifle at your target and hit with a minimum of variation out to a given distance.

Note that the height of the sights, cross-hairs, or reticle above the bore of the rifle will affect the what distance that you should zero your rifle to achieve the flattest trajectory. If you are using a scope mounted with the reticle or crosshairs that sit ~2″ above the bore, the best zero distance for the flattest trajectory is going to be different that using the factory iron sights that sit ~.6″ above the center of the bore.  Also, you will get different performance from different brands of ammunition and different weights of bullets.

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Establish A Set-It-And-Forget-It “Battle Sight Zero”:

My goal was to figure out a best set-it-and-forget-it “battle sight zero” setting on my Ruger 10/22 that would allow me to get the best accuracy at varying distances without worrying about holdover.  I used an iPad/iPhone app called Ballistic v5.0.6 to analyze different trajectories for different ammunition loads and different zero settings at various distances to see which trajectory is the flattest.  The data that I have provided below is for Federal “Bulk Pack” 36 grain hollow-point ammunition and CCI Mini-Mag 36 grain hollow-point ammunition.  I chose these rounds because that is what works most reliably in my Ruger 10/22, and that’s what I have plenty of.  I can’t guarantee reliability with these two loads of ammunition in any other semi-automatic rifle besides a Ruger 10/22, but if your rifle will shoot these loads then these are the ballistic results that you should expect.

I have provided data for shooting with the factory sights that sit 6/10″ above the center of the bore, and also for optics with a reticle that sits 1.5 inches above the center of the bore (such as the Bushnell TRS-25, shown right).  There will be data on Federal ammunition used with factory sights sitting 6/10″ above the bore as well as optics with the reticle sitting ~1.5″ above the bore, and data on the CCI Mini-Mag with sights sitting ~.6″ above the bore and optics with the reticle sitting ~1.5″ above the bore.  I have only analyzed trajectories through 100 yards as the performance of the .22LR is anemic at best beyond that distance.

Pick your rifle configuration (with or without an optic), pick your ammunition, and then pick the best (flattest) shooting zero for your rifle.

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Factory “Iron Sights” ~.6″ Height Above Bore:

Federal “Bulk Pack” 36 Grain Hollow-Point:

The chart above (click on it to enlarge) assumes that you are using the factory “iron sights” with a ~.6″ height over bore.

The chart shows three different trajectories from three different zero settings.

The 10-yard zero trajectory is represented by the green arc.  The bullet’s arc rises up through point-of-aim at 10 yards and back down at approximately 52 yards.  It has the highest rise above point-of-aim (.52″ at 30 yards).  The 10-yard zero will suffer the least in the long run, falling to ~3.38″ at 75 yards and to ~6.15″ below point-of-aim at 100 yards.  You will be able to hit within a 1″ circle from just a few feet from the muzzle out to approximately 59 yards.

The 12-yard zero is represented by the red arc.  The bullet’s arc rises up through point-of-aim at 12 yards, should apogee ~.27″ above point-of-aim between 25 and 30 yards, and then descends back through point-of-aim at approximately 42 yards.  With the 12-yard zero you have the opportunity to hit within a 1″ diameter circle around the aiming point starting at the muzzle and traveling out to around 52 yards.  After that the trajectory drops rapidly and hits ~7.33″ below point-of-aim at 100 yards.

The 15-yard zero, represented by the blue arc, has the least rise over point-of-aim (only .08″… for practical purposes we will go ahead and say that it doesn’t rise over point-of-aim), and at 100 yards the bullet falls 8″ below point-of-aim.

Recommendation:  If the farthest distance that you ever plan of shooting your rifle is 50 yards then you might entertain the idea of the 12-yard or 15-yard zero.  If you plan on shooting past 50 yards and out towards 100 yards I would recommend the 10-yard zero, then memorize the dope or make a range card, and practice at various distances to learn where the rifle will shoot.  Plan on a 6″ drop at 100 yards.

CCI Mini-Mag 36 Grain Hollow-Point:

The chart above (click on it to enlarge) assumes that you are using the factory “iron sights” with a ~.6″ height over bore.

The chart shows three different trajectories from three different zero settings.

The trajectories of the CCI ammunition are almost identical to that of the Federal (close enough that you won’t be able to tell a difference).  Be sure to take a look at the above analysis of the Federal ammunition with the factory sights.  With the CCI ammunition it looks as if you will not have any improvement with trajectory over the Federal ammunition.  CCI may offer better reliability as it is a little cleaner burning and takes longer to foul the rifle.  Also, you may find CCI ammunition to have better terminal effects on target.  Your results may very.

Recommendation:  Like with the Federal ammunition, if the farthest distance that you ever plan of shooting your rifle is 50 yards then you might entertain the idea of the 12-yard or 15-yard zero.  If you plan on shooting past 50 yards and out towards 100 yards I would recommend the 10-yard zero, then memorize the dope or make a range card, and practice at various distances to learn where the rifle will shoot.  Plan on a 6″ drop at 100 yards.

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Optic Mounted With Aiming Point 1.5″ Height Above Bore:

Federal “Bulk Pack” 36 Grain Hollow-Point:

The chart above (click on it to enlarge) assumes that you are using an optic with a ~1.5″ height over bore, such as the Bushnell TRS-25 red-dot (notice that the bullet leave the barrel 1.5″ below line of sight).

The chart shows three different trajectories from three different zero settings.  The 20 yard zero (blue line) provides the least drop at long distance with only minimal flight over the point of aim.  The 25 yard zero (red line) and 30 yard zero (green line) have very little (if any) rise over the point of aim, but their trajectories suffer significantly at longer ranges, dropping as much as ~5.75″ at 100 yards.

Assuming a 20-yard zero, the bullet will have point-of-impact at the same spot as point-of-aim at 20 yards, and again at approximately 59 yards.  Between 20 yards to 59 yards there is maximum rise of approximately 1/2″ over the point-of-aim (which will occur at 49 yards).  Keep in mind that technically you would have to aim 1/2″ low to hit exactly where you are aiming at 49-50 yards, but the red-dot in the TRS-25 (and most similar optics) is 3 MOA.  This means that at 50 yards the dot appears ~1.5″ wide.  Without any holdover the bullet will still hit within the red-dot.

At approximately 78 yards the bullet will drop down the same distance below your point-of-aim as when it left the barrel (1.5″). This means that from the muzzle out to 78 yards you will get a trajectory that never rises more than 1/2″ above where you are hitting, and never more than 1.5″ below your point of aim.  After 78 yards the bullet’s trajectory will continue to drop down and impact approximately 4.36″ below your point of aim.  Keep in mind that your red-dot (assuming a 3 MOA dot) will appear 3″ wide at 100 yards.  This means that the bullet will impact just below the dot.  If you simply rest the dot so that it is resting right on top of the target (like a crown) you bullet will drop down right where you want it.

With the 20-yard zero you can expect hits within a 1″ circle of your point of aim from the 12 yards all the way out to 67 yards without having to worry about adding any holdover to your aim. This makes it easy to hit a target the size of a tennis ball or a squirrel out to 67 yards simply by placing the red-dot where you want to hit and then applying the seven principles of marksmanship.

Recommendation: When using a rifle with an optic mounted so that the reticle is 1.5″ over the bore, and shooting Federal “Bulk Pack” ammunition, use a 20-yard zero setting.

CCI Mini-Mag 36 Grain Hollow-Point:

The chart above (click on it to enlarge) assumes that you are using an optic with a 1.5″ height over bore, such as the Bushnell TRS-25 red-dot (notice that the bullet leave the barrel 1.5″ below line of sight).

The chart shows three different trajectories from three different zero settings.  The 20 yard zero (blue line) provides the least drop at long distance with only minimal flight over the point of aim.  The 25 yard zero (red line) and 30 yard zero (green line) have very little (if any) rise over the point of aim, but their trajectories suffer significantly at longer ranges, dropping as much as 5.79″ at 100 yards.

The CCI Mini-Mag is a slightly hotter round than the Federal.  On the graph you will see a slight increase in the apogee of bullet’s flight (measured in 100th of an inch) and only .36″ difference in drop below point-of-aim at 100 yards.  I seriously doubt that you will notice a difference when shooting.  The only benefit may be the increase terminal performance of the CCI Mini-Mag.

Looking at the data of the 30-yard zero we see that the round barely clears the point-of-aim between 30-45 yards, and then rapidly falls and impacts 5.79″ below point-of-aim at 100 yards.  The 25-yard zero climbs over the point-of-aim at 25 yards and only reaches approximately 2/10″ before falling back through point-of-aim again at 50 yards.  This is a pretty flat trajectory, but the 30-yard zero looses its attractiveness as it drops down to 5.37″ below point-of-aim at 100 yards.  Still, it is a good zero.  You can enjoy hits within a 1″ circle (1.2 inch above or below point-of-aim) from 15 yards out through 62 yards.  Your penalty will be hitting almost an inch lower at 100 yards than the 20-yard zero.

A 20-yard zero will see the bullet climb through point-of-aim at 20 yards and not drop back through until approximately 62 yards, during which time the bullet will only climb to a maximum of .56″ at 40 yards.  This is only .37″ higher than the maximum apogee of the 25-yard zero’s trajectory.  This is still very close.  Like in our analysis of the Federal ammunition we need to keep in mind that at 50 yards the 3 MOA dot of optic will appear as 1.5″ wide.  The bullet will still hit within the red dot with or without holdover.  If you are concerned with .37″ at 50 yards then a red-dot optic is not appropriate for your shooting needs.  Where you will enjoy the benefits of a 20-yard zero is that the bullet only impacts 4.44″ below point-of-aim at 100 yards.  The 3 MOA dot will appear as 3″ wide at 100 yards.  As with the Federal ammunition, simply put the red-dot over the intended point-of-impact (like a crown) and the bullet will drop right down where you want it.

Like the Federal ammunition, with the 20-yard zero you can expect hits within a 1″ circle of your point of aim from the 12 yards all the way out to 67 yards without having to worry about adding any holdover to your aim. This makes it easy to hit a target the size of a tennis ball or a squirrel out to 67 yards simply by placing the red-dot where you want to hit and then applying the seven principles of marksmanship.

Recommendation:  While the 25-yard zero is very attractive, I would still recommend the 20-yard zero.  While there is s a very slight penalty of higher apogee of flight with the 20-yard zero, you get almost one inch less drop at 100 yards.

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AR-15 Style Rifle With Sights Or Optic 2.5″ Height Above Bore:

.22LR In The AR15:

The shortage and rising prices of ammunition has made dedicated .22LR AR-15 rifles, and conversion kits for 5.56mm/.223 caliber AR-15 rifles very popular. Unfortunately the recent shortage of .22LR ammunition has made it hard to feed them if you didn’t already stockpile (hoard) .22LR ammunition. If you are lucky enough to have access to .22LR ammunition then the dedicated .22LR AR-15 rifles or the conversion kits for your 5.56mm/.223 caliber AR-15 rifles are fun for target shooting and plinking, and can be a great tool for teaching new shooters without the loud noise and high price of full-size center-fire ammunition.

What Distance To Zero For .22LR Ammo With AR Style 2.5″ Tall Sights:

A friend recently acquired one of Colt’s .22LR M4 rifles made by Walther Firearms and asked if I would help zero the sights at the appropriate distance.  I had never really taken dedicated .22LR AR-15 rifles seriously until I was asked to help zero this rifle.  Any traditional .22LR rifle has its sights mounted close to the bore, and traditionally red-dots are always mounted as close to the bore as possible.  I couldn’t see how you could have anything but a terrible .22LR ballistic trajectory with AR-15 sights that are 2.5″ above the bore.

Having been granted the opportunity to play with this rifle for a few days, I ran a few zero distance calculations through an iPhone/iPad application called “Ballistic” using data for CCI’s 36-grain Mini-Mag ammunition, and I couldn’t believe how ignorant I had been. You can achieve a very flat trajectories from .22LR ammunition and 2.5″ high sights. I played with several distances and tweaked it until I found the optimum zero distance of 25 yards.

I have had the chance to shoot the dedicated .22LR Colt M-4, as will as a civilian M4 equipped with a CMMG .22LR conversion kit.  The 25 yard zero worked fantastic with both!

25 Yard Zero:

Firing .22LR from a rifle with sights 2.4″ to 2.5″ height above bore (such as with an AR15), the 25 yard zero will give you the flattest trajectory out to 100 yards.

Note the graph above. From a distance of 13 yards from the muzzle, all the way out to approximately 89 yard, the point-of-impact of the bullet will never be +/- 1″ from point-of-aim. This means that you should be able to hit a 2″ target without any hold-over / hold-under correction anywhere within 13 yards to 89 yards!

The highest distance above point of aim is exactly 1″ at 50 yards.

At 100 yards you can expect your point-of-impact to be 2.37″ below your point-of-aim. To give you a visual, you will make hits below the point-of-aim less than the height that the sights set above the bore. This is pretty impressive, especially considering that you might be using a red-dot optic, such as the Bushnell TRS-25, with a 2 minute-of-angle dot (dot that appears 2″ in diameter at 100 yards).

Dedicated .22LR Rifle:

If you have a dedicated .22LR rifle then you have a simple task of zeroing your rifle’s optic and/or iron sights. Zero it for 25 yards and you are done. Congratulations!

AR15 With CMMG .22LR Conversion Kit:

If you have a CMMG conversion kit and want to accurately and effective use 5.56mm NATO ammunition as well as .22LR ammunition with the CMMG conversion kit, you will want to check out:

• Savannah Arsenal’s CMMG Brand Conversion Kits For AR-15 Rifles

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Related Articles:

• Savannah Arsenal’s Rimfire Ammunition Page
• Savannah Arsenal’s Rimfire Optics & Accessories Page
• Savannah Arsenal’s Rimfire Conversion Kits Page
• Savannah Arsenal’s Ruger 10/22 Rifle Page
• Savannah Arsenal’s Henry Arms .22LR Page
• Savannah Arsenal’s Marlin 60 .22LR Page
• A Great Red-Dot Optics For .22LR Rifles: Bushnell TRS-25
• Bushnell Trophy Red-Dot: No-Go!
• What Distance To Zero Your .22LR Conversion Kit Equipped AR-15 or Dedicated .22LR AR-15
• Make A New Storage Tube For Your AR-15 22LR Conversion Kit
• CMMG Brand Conversion Kits For AR-15 Rifles
• Gemtech’s Subsonic .22LR Ammunition = WIN!

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