How To Zero Your AR1. Rifle. By Tom Mc. Hale. Eyesight is straight, while bullet flight paths arc. Tom Mc. Hale. USA Ammoland. Today were going to do complicated mathBut in the end we will answer that question, how to zero your AR1. Well be talking about AR1. Fortunately we will not be talking about shooting in zero gravity as bullets would fly forever, or at least until they crash into the drifting hulk of the Discovery One. Fortunately, its not as complicated as deciphering the true meaning of White House press briefings, as long as you understand how bullets fly. Bullet trajectory is almost as simple as dropping a brick, except the bullet flies forward where a brick just drops towards the ground. When you fire a bullet, there is no magical force that helps it defeat gravity. In fact, if you fire a bullet from your AR type rifle, perfectly parallel to the ground, the bullet you fire will end up hitting the ground at just about the same time as a bullet you let fall from your hand straight down. I say, just about only because the earth curves a bit, and the fired bullet will have a smidge farther to fall than the dropped one. Its that gravity thing we just cant defeat, no matter what. No matter how fast a bullet is flying, its constantly falling towards the ground. Even bullets fired from those so called High Powered Assault Weapons. If you look at the path of a bullet, it will always be a downward sloping curve, kind of like congressional approval ratings. But wait, you say, when I aim right at a target 1. Thats correct, but only because the barrel is actually pointed a little bit upwards relative to the ground. Shooting a bullet is a just like throwing a football except you dont get 1. You need to aim it up a little bit so it arcs back down to intersect at your desired impact point. See Bullet Flight Path image aboveMost AR optics are about 2 12 inches above the bore line. Whether you use iron sights or a fancy optic on your AR rifle, you will always need to plan for the intersection of the straight line designated by your line of sight and the arc of the bullet. Your line of sight is not subject to the laws of gravity, so you see in a perfectly straight path, unless you stayed out too late last night. Since your bullet leaves the barrel in an arc pattern, it may actually intersect your line of sight twice once on the way up, and again on the way down. But that depends on your zero distance. Think about it. Your sight is already about 2 inches higher than the center of the bore, so the barrel HAS to be aimed up a bit if it ever hopes to intersect with the line of sight. Zeroing your rifle simply means configuring your sights, iron or optics, so that at some desired distance, your line of sight perfectly intersects the path of the bullet. If this seems confusing, just think back to the example of throwing a ball. If you throw exactly at the target, the ball will hit the ground before it gets there. Because of gravity. 6mmBR. com is the best guide for 6mm BR Benchrest precision shooting, complete with 6BR FAQ, Reloading Data, Shooter Message Boards, Reader Polls, and Photo Gallery. Need ballistics data but dont have a program Youre in luck. Check out JBMs realtime interactive online ballistics calculator. Its very fast, very accurate, and. im currently in the market for an AR, and ill probably going to get it from rock river. while comparing prices, it seems that building it will save. Corrosive Ammunition One fact holds true for all production regardless of year or country, and that is all surplus 7. 62x54r ammunition is corrosive. PRICE LIST ITEM 44A Chrony Ballistics II Software, plus IBMPC Interface 79. 95 U. S. ITEM 37 Chrony Ballistics II Software 66. 95 U. S. If you arc it up a bit, gravity will bring it back down, and if you calculated right, that would happen right where your teammate is ready to catch it. There is one more variable to consider and thats the velocity of your specific bullet fired from your rifle. No matter what the velocity, gravity still rules. A faster bullet will not defy gravity any more effectively, but it will fly farther in the same amount of time, so there is an illusion that it defies gravity better than a slower projectile. So, with a faster bullet, those curves we just discussed will appear to be a bit flatter, but thats just because the bullet travels farther forward in the time it takes to fall to the ground due to the effects of gravity. For purposes of this discussion, well assume that were talking about a. Remington or 5. 5. Since the whole idea of zeroing is to line up your sights with the impact point of a bullet, you can set your zero just about wherever you want. But first, remember that the sightline is 2 inches give or take depending on your equipment above the bore. For purposes of this discussion, our examples will assume were using a standard 5. Remington cartridge. If you set your zero close, say at 1. The barrel has to be angled up pretty severely for the bullet to move up 2 vertically in such a short distance. As a result, after the bullet crosses the 1. Farther down range, say at 1. If you set your zero at 5. The barrel is angled less aggressively towards the line of sight. With a 5. 0 yard zero, your bullet will only be about 1. From then on, its all down hill again. Finally have that AR15 and now you need to know how to zero your AR15 rifle. Sighting in the rifle is the process tom Mchale takes us through. Article. Chrony Ballistics II Software is designed to work with Microsofts 32bit operating systems Windows 95, Windows 98, Windows 98 Second. If you set your zero at 1. Coincidentally, with a 1. As soon as it intersects the line of sight at 1. As you can see, you have some decisions to make depending on how you anticipate shooting. If every single target you will ever shoot will be at the exact same distance, then set your zero for that distance. However, this is kind of unrealistic. Most people will need to be able to hit targets at different ranges, so you need to compromise. The most common approach to settling zero distance compromises is to think in terms of acceptable impact zone. For example, if your shot impacts within, say, 3 inches above or 3 inches below your point of aim, that might be good enough for the job at hand. If this outcome is desired, then your job is to find the zero that prohibits the bullet from traveling more than 3 inches above the line of sight. At some point down range, the bullet will fall more than 3 inches below your line of sight. That will be your maximum range where you can hit your target closely enough without adjusting your aim point. As an example, lets look at the 5. By definition, the bullet arcs upwards until it reaches the line of sight at 5. It continues traveling above the line of sight until it peaks at 2. Now the bullet obeys gravity and starts to drop. At 3. 00 yards, its fallen to about 4. If youve been paying attention, youll note that the total vertical range is only about 6 inches 2 inches above the line of sight and 4 inches below anywhere from zero to 3. If hitting in a 6 inch circle is good enough, you can aim directly at your target as long as its anywhere inside of 3. You might hear this concept called point blank range. It just means you dont have to make any adjustments for targets within that range. A look at how 2. 5, 5. I like to zero my. Remington or 5. 5. First, it gives me point blank aiming capability out to 3. Remington 5. 5. Second, most of my optics are in the 1x to 6x magnification range, and I can aim very precisely at the 5. Third, my eyes are old. I can only actually see targets within 3. If you choose a shorter zero distance, say 2. Your sight is still about 2. Thats OK as long as you realize that the bullet will travel higher above the sight plane while on its path downrange. The reverse concept applies if you choose a longer range zero. Between your firing position and your zero point, the bullet will always be within 2. After the zero point, since the bullet has been in the air longer to get there, it will rapidly fall away and youll have to account for how far below your line of sight it is at a given distance. As you can see, setting the zero on a standard AR rifle is all about compromises that factor in your anticipated target range. Ive just found that a 5. Recommended Tools About. Tom Mc. Hale is the author of the Insanely Practical Guides book series that guides new and experienced shooters alike in a fun, approachable, and practical way. Compensators Pressure or Gas Shooting Times. We often hear arguments that high pressure is required to make a pistol compensator work properly. Some people claim that compensators are ineffective with. ACP because the cartridge doesnt produce enough pressure. It is a relatively low pressure round with a maximum average pressure limit of 2. CUP when measured with that method. Some argue that compensators only work on high pressure cartridges, like the. Super. Its maximum average pressure limit is 3. CUP, and theres no doubt compensators work very well with. Super. I set out to test if a compensator works with the. ACP like it does with the. Super. During testing, it was important to understand how gunpowder contributes to recoil, and not just that adding more gunpowder produces more recoil. Because youre also increasing velocity recoil goes up regardless. The key is more gunpowder weight for the same velocity. Gunpowder charge weight contributes to the overall recoil force. Newtons Second Law describes force as the product of mass and acceleration. F ma Force equals mass times acceleration. The gunpowders weight is part of the mass that exits the end of the barrel the ejecta in the form of gas along with the bullet. Formulas that calculate recoil force also require the gunpowder weight, bullet weight and velocity for an accurate calculation. This means that if you compare two different gunpowders that produce the same velocity but require different charge weights, the powder that requires a larger charge weight produces more recoil. More gunpowder weight means a greater volume of gas. Compensators deflect gas to help tame recoil. Pistol compensators usually direct the bulk of the gas upwards through large ports. As the gas blasts upward, it produces an equal amount of downward force to help counteract muzzle climb. The downward force is also explained by Newtonian physics that for every action there is an opposite and equal reaction force up force down. In a non compensated pistol, gunpowder with a higher charge weight produces more gas and thereby more recoil and muzzle rise than a lower charge weight gunpowder even though they produce the same velocity with the same bullet. Effective compensator function will reverse this gas volume effect on recoil the higher charge weight gunpowders additional gas will generate more downward force and produce less muzzle rise than a lower charge weight gunpowder. Testing. Four gun configurations were required for the test, a compensated and non compensated version for each caliber. ACP and. 3. 8 Super. The non compensated configuration was used to show how gunpowders normally affect recoil, which helps to demonstrate how compensators work to reduce muzzle rise. The. 4. 5 ACP test gun was a Para Ordnance P1. Les Baer slide with a Clark 5. The. 3. 8 Super test gun was a Para Ordnance P1. Bar Sto threaded bull barrel with a three chamberport compensator plus an additional Caspian slide with a 5 inch Kart barrel. The two compensators had nearly identical port sizes. All the ports vented upward as neither compensator had side ports. The guns were fired from a Ransom Rest. Measuring the distance that the gun moves in the Ransom Rest indicates relative recoil. Velocity was measured at about 1. Shooting Chrony chronograph. Ten rounds were tested with each load. Test ammunition was loaded in same headstamp brass with 2. FMJ bullets in the. ACP and 1. 15 grain JHP bullets in the. Super. Two gunpowders were used Hodgdon Titegroup and Accurate No. Three charge weights were loaded for each gunpowder. Its important to note Titegroup is a fast burning gunpowder and requires a much smaller charge weight than the slower burning Accurate No. Charge weights required to achieve 8. ACP and 1. 27. 5 fps in the. Super were calculated with linear regression based on the results with no compensator and are shown in Table 1. The difference in charge weights between the two gunpowders is almost two fold for both calibers. Data from the. 3. Super illustrates how the differences between the two gunpowders affect recoil. In a standard pistol with no compensator, Accurate No. Titegroup powder for the same velocity. Figure 2 shows the recoil profiles of the two gunpowders. The line representing Accurate No. Titegroup line, indicating more gun movement recoil for the same velocities. With a compensator, the position of the profiles is reversed, and the Accurate No. Titegroup line. Thus, the higher charge weight gunpowder produced more movement with no compensator and less movement with a compensator. Titegroup showed a 6. Accurate No. 7 showed a greater reduction of 7. This shows the charge weightgas volume compensator effect the higher charge weight gunpowder shows a greater reduction in muzzle rise. Data from the. 4. ACP shows the same result Figure 3. Accurate No. 7 produces more movement than Titegroup with no compensator, and less movement with a compensator. Titegroup showed a 4. Accurate No. 7 showed a larger 5. These data demonstrate that a compensator works effectively with the low pressure. ACP cartridge and in the same manner as the high pressure. Super. The. 4. 5 ACP showed less overall recoil reduction 4. Super 6. 8 7. 9. This is most likely attributable to the. Part 2 Chamber Pressure. I took a second approach to the pressure versus gas volume debate. I made a comparison between gunpowders with loads of known published pressures to compare the effect of different pressures on recoil. The published numbers represent peak chamber pressure. How this translates into gas pressure at the compensator is a different issue. Pressure at the compensator is what matters, because this is where the force is applied. Therefore, the chamber might not be the right place to measure pressure for this purpose, but this test is necessary to evaluate the role of chamber pressure. Gunpowders were selected based on published pressure and charge weight data available on Hodgdons website.   Again, I tested. ACP and. 3. 8 Super. I tried several gunpowders from the Hodgdon data Super Target, Titegroup, Auto. Comp, 2. 31, Longshot, HS 6 with the hope of getting some that would yield similar velocities since one cannot predict the actual velocities produced by a particular gun. Similar velocities are necessary for this comparison. The data are from Winchester 2. Hodgdon Longshot in the. ACP, and 2. 31 and Hodgdon HS 6 in the. Super Table 2. The 2. Charge weight differences between the low and high pressure loads were at least one grain. The actual pressures in my guns would likely not exactly match the published pressures, but the relative differences in pressure should be maintained since these reflect characteristic differences of the gunpowders. I used the same bullet and overall length as the Hodgdon data Hornady 2. FMJ FP bullets for the. ACP loaded at 1. 2. OAL in same headstamp cases, and Hornady 1. XTP bullets at 1. OAL in same headstamp cases for the. Super. Recoil and velocity were measured as previously described. Ten rounds were fired with each load. In the. 4. 5 ACP, Longshot LS powder, with its larger charge weight, produced more movement than 2. Figure 4. Similarly, in the. Super, HS 6 powder, with its larger charge weight, produced more movement than 2. Note that Longshot and HS 6 both produced more velocity than 2. These results show that higher chamber pressure does not mean better compensator function.