Been there, done that...
I made up a little cheat sheet with all kinds of useful information on it. It's all the little things that you tend to forget or people want to argue about. I got it laminated and it stays in my range bag.
In fact, I had the same problem tonight trying to sight in my .22 for the Virtual Match.
Out came the card, and all my problems were solved....well...except for the fruitcake behind the trigger.
esheato....
Ballistics Information
-Determine shot size:
-----17 - shot # = diameter
-Convert FPS to MPH:
-----FPS / 3 * 2 = MPH (+- 3%)
-----FPS * 0.6818
-Convert POUNDS to GRAINS
-----POUNDS * 7000 = GRAINS
-----GRAINS / 7000 = POUNDS
-Determine KINETIC ENERGY – WV^2 / 450400
-----W = weight of bullet in grains
-----V = velocity in FPS
-Determine approximate shotgun range:
-----2,200 * (shot diameter)
-----7 ½ 209 yards
-----9 176 yards
-DRAM EQUIV. = >27 grains (27 11/32 grains)
-GENERAL RULE – less choke is needed if the shot size is increased and more choke is the shot size is reduced
-PELLET WIND DRIFT – No. 7 or 8 shot can be expected to be deflected about 7-8†in a 10 MPH at normal range
-PROPER EXPANSION REQUIRES PROPER VELOCITY – most JHP won’t expand properly below 900 FPS
-BALLISTIC COEFFICIENT – a measure of how well a bullet can overcome air resistance and maintain flight velocity. The higher number the more efficient. Three points govern BC; weight, diameter and shape
-OGIVE – the curve between the bearing surface and the point
-MEPLAT – point of a bullet
-FREE BORE – peak performance occurs at 0.00 to 0.020â€
-CRIMP GROOVE – less inherent accuracy because the bullet is deformed in an area that disrupts the flow of air and reduces aerodynamic stability
-Determine bore diameter:
-----Bore diameter is before the grooves are cut in the barrel. (land distance) After the grooves are cut, this larger diameter is the bullet’s diameter. Groove depth is normally 0.004-0.006â€
-GYROSCOPIC DRIFT – bullets drift to the right when fired from right twist barrels and to the left when fired from left twist barrels
-RICOCHET – bullets ricochet at the angle of incidence; Shallow = shallow; steep = steep
-Determine barrel length:
-----REVOLVER – distance from the rear of the forcing cone to the muzzle, not including cylinder length
-----RIFLE/SHOTGUN/PISTOL – entire bbl length with action closed; chamber length included
-BARREL WEAR – lands wear the most starting at the chamber; primary source is bullet friction
-MUZZLE BLAST – expanding gas leaves the muzzle at a speed much higher than the speed of the bullet; normally 1 ½ times the bullets velocity
-RECOIL – recoil increases as the square of the velocity; recoil also increases as the square of the bullets weight. The bullets weight and its velocity have a larger influence over recoil than does the guns weight
-PEAK PRESSURE – occurs and measured before the projectile has moved a maximum ¼ the length down the barrel; normally 1-1.5 inches in bbl length
A 3% increase in velocity will be accompanied by a 6% increase in chamber pressure
-Determining pressure:
-----Copper crusher used for pressures over 15,000 psi
-----Lead crusher used for pressures under 15,000 psi
-60% of a propellants energy is unused for the purpose of propelling the projectile
-----1-2% of chemical energy will be wasted in unburned fuel and simply blown out the muzzle into the atmosphere; most likely observed as muzzle flash.
-----2-4% of mechanical energy lost to friction
-----25% lost to thermal energy to heat the barrel
-----30% lost in thermal energy (hot gas expelled at muzzle)
-GENERAL RULE – 1 grain propellant/ 3 grains of bullet weight will NOT be too much for proper volume between case and bore
-GENERAL RULE – anything that increases pressure will also increase the burn rate, which will in-turn affect peak pressure location in the bore
-SIGHT ADJUSTMENT – rear sight is moved in the direction that you want the projectile to go The front sight is moved opposite the direction that you want the bullet to go
-SHOOTING ON A SLOPE – the projectile will always strike higher on a slope
-COOKING-OFF:
-----RIFLE/PISTOL – high 200 F, low 300 F
-----SHOTSHELL – high 300 F
-PRIMERS – BOXER system developed by UK, used here…BERDAN system developed in US, used in UK
2 sizes -- .175†and .210â€
-BLACKPOWDER:
-----FFFg – smallest particles, fastest burn rate; handguns
-----FFFg – small bore rifles
-----FFg – small bore rifles
Generally, the faster a powders burn rate, the more velocity produced (assuming equal charge weights)
-RELATIVE QUICKNESS – equal to the time that a propellant uses to burn up completely.
Hopefully nobody will dispute my information, as I got it from a ballistics book.
