PSW and FFS Software
A Brief Tutorial
How to Get the Most out of this Software

This software incorporates a set of tools for the shooter to wring the most out of his equipment and to maximize the chances of a cold-bore, first round hit on target. To use the tools requires a certain level of competence and effort. If the shooter either does not have the level of knowledge necessary to engage this software or does not want to expend the effort necessary to develop the data necessary to create useful and meaningful trajectory output, then he will not be able to get the most out of his software investment.

Preparing to Use this Program
Three Important Steps

Calibrating the Scope - The only way a shooter knows how much his bullet actually drops over distance is by using the elevation turret of his scope to tell him how much elevation was required for the shot. What if the turret isn’t accurate? What if the click value of the scope isn’t what the manufacturer says it is? What if the click value is off by 4%, 7% or even 10%? For example, a Leupold Mk V, M3 is advertised to have a 1 MOA per click turret. A shooter who is shooting the .308 Win cartridge may find that it takes 42 clicks from a 100-yard zero to be on target at 1000 yards shooting M118LR ammunition and would therefore assume that for the conditions at hand, the bullet drops 42 MOA at 1000 yards and any computer program that forecasts a different theoretical result is simply wrong. After all, one doesn’t argue with reality.

If the shooter were to put on another scope on the same rifle, he would expect to dial in 42 MOA and be right on target. That may or may not be the result, however, because it is not necessarily the case that the turrets on the scopes are moving the reticle the same amount - on scope one, the turret says 42 MOA but in reality it may have moved the reticle only 40.7 MOA; on the second scope the turret says 42 MOA, but it may have moved the reticle 42.9 MOA. Just because the manufacturer says that a given turn of the turret moves the reticle a given amount on the target is NO assurance that it in fact does. The shooter needs to check. This is the essence of scope calibration.

The first thing any long range shooter must do is calibrate his scope to determine exactly how much the reticle moves with each click of the turret and NOT to take the manufacturers word for it. The desktop program allows the user to print out five sheets of 8½ X 11 paper, each with chart lines printed thereon. Assemble the five sheets in order on a cardboard backing of some sort and place the chart at 100 yards or meters. (If the desktop program is not available, just take a long sheet of paper about 45 inches long, put a visible mark at the top and one at the bottom. Use the top mark as the starting point and move the reticle to the bottom mark.) Fix the rifle in a vise or with sandbags, dial the scope to zero, align the horizontal element of the reticle at the “0” (or top) line on the chart and then dial in 40 or so MOA and watch the reticle move down the chart. Keep track of the number of clicks of the turret and note the line number on the chart. Do this a few times to assure an accurate measurement. Now that the number of clicks has been recorded for a known distance of travel, double check the distance traveled on the chart by measuring the distance on the chart with a tape measure. Then use this data to compute the ACTUAL click value of the user’s scope. The program has a computation dialog box for this purpose and requires as inputs the actual and accurate range at which the measurements were taken, the number of clicks of the scope, and the corresponding distance the reticle moved on the chart or target. Once the user knows the actual click value of his scope, he can use this value 1) to compute the actual drop of the bullet at range; and, 2) to compute the exact turret setting for any firing solution computed by the software. This value is used in the Turret Profile so the program can accurately calculate a turret setting for any given drop.

In obtaining this data it is important that the shooter accurately measure the actual distance between the scope at its turret and the face of the target. Use either a good rangefinder (one that has an error factor of under a yard, hopefully in 10ths of a yard) or a tape measure. Errors in distance will have a definite effect on the calculations. You only have to do this once for each scope, so do it carefully.

Obtaining Muzzle Velocity – Any ballistics program, this one included, must have the muzzle velocity of the bullet for each cartridge used by the shooter. But the velocity of a bullet measured 15 or so feet away from the muzzle, where the chronograph is located, is not the muzzle velocity. The program has a dialog box to help the user calculate what the actual bullet velocity at the muzzle given the measured velocity at the chronograph. Further, it is necessary that when the chronograph data is collected the shooter also notes the air temperature at the time. Why? Because when shooting the same cartridges later the temperature may not be the same which means that the powder temperature will not be the same which means that the muzzle velocity may not be the same. By noting the temperature that existed at the time the chronograph data was obtained, the shooter can input that data in a Bullet Profile and allow the program to correct the muzzle velocity for temperature. Therefore, with the actual muzzle velocity computed at a known powder temperature, the shooter can be assured that the proper muzzle velocity will be used by the program when computing a firing solution in the field.

Computing the DK - Most all ballistic programs will compute a trajectory based upon muzzle velocity, bullet configuration (i.e., the ballistic coefficient), and atmospheric conditions. This program uses the same data. BUT, this program also calibrates or customizes the trajectory to the cartridge/rifle/shooter. The manner in which a shooter manages his rifle, i.e., the interface between shooter and rifle, differs from shooter to shooter, rifle to rifle. This is one reason why two shooters who shoot the same rifle using the same ammunition can have bullet groups located at two different spots on the target. To have truly accurate trajectory computations, it is necessary to tailor the trajectory computation to the cartridge/rifle/shooter system and this program allows the user to do that.

The user must determine the actual bullet drop at sufficient range but where the bullet is still supersonic but at a point where the bullet has experienced significant drop. This range will differ depending upon the bullet in question but it is suggested that the user find a range where the bullet is moving between 1200 to 1400 fps. The following is an example of how to go about computing a DK. Let us suppose that a shooter is attempting to calibrate the trajectory for a 190 gr. Berger VLD which he uses in a 300 Win. Mag.. He chooses to measure the bullet’s drop at the 1000 yard range believing the bullet to be well above the speed of sound at that range. He uses the program to determine that under the conditions present at the range during this test, the bullet's velocity at 1000 yards is approximately 1435 fps. That is close enough. The shooter records the atmospheric data (air temperature, humidity and pressure) and takes three to five well-aimed shots. He records that his scope (which he has calibrated as described above) used 27.384 MOA to get the bullet on target with a 200-yard zero and that the program predicts a 27.4 MOA bullet drop. Upon studying the targets, he notes that the group is actually 6 inches below point of aim, so in actuality the bullet drop was 27.957 MOA (6 inches equals 0.573 MOA. Add 0.573 to the actual MOA correction dialed by the scope.) Using this data, the shooter computes that bullet’s DK by inputting the data in the DK computation dialog form supplied in the program. For this bullet under the existing atmospheric conditions, the program computes a DK of 0.498. When the shooter uses the same atmospheric data, muzzle velocity, ballistic coefficient and DK to compute the trajectory for that bullet, the program correctly predicts a bullet drop of 28 MOA. The trajectory has been calibrated for that bullet/rifle/shooter system and as the weather conditions change or muzzle velocity changes, the program will still accurately compute trajectories for that system as long as the system does not change. This means that if the shooter changes the manner in which he assembles his cartridges, changes the powder, changes his firing position, he needs to check the impact points to make sure the DK is still valid. It is a good idea to compute a DK for each cartridge and rifle combination the shooter owns.

The default DK of 0.5 is a good place to start and many have found that it suffices for all but the most demanding work. If extreme accuracy at extreme ranges is required, however, the user should take the time to compute a custom DK.