Re: Real World vs. Calculated trajectory for .22lr
My policy with .22lr has always been to take a roll of paper into the woods, tape it to the side of a tree, and shoot at the same spot (as high up as you can reach to make a dot) from 50 - 500 yards and record results. Sometimes you can wait for a certain wind condition and get a solid group that will give you some good wind data as well. I then go back to the computer and "reverse engineer" the numbers to get what I found in the field (AKA truing). I use Bryan Litz's Applied Ballistics for Android app on my phone to run all calculations (I trust Bryan's #'s). However, I can't use the program's built-in truing feature because the rounds are subsonic around 75 yards, which messes up his software. I believe that he will be fixing this in the next update.
What you have to remember is that as the bullet goes through transsonic flight, it wobbles a little, which makes it less aerodynamic and the B.C. drops. It is also perpetually slowing down, thus the B.C. is further dropping. In high caliber weapons, these effects don't come into play until around 800 yards (for .308 w/ 175 SMK). For .22lr, these conditions pop up around 75 yards. Therefore, to accurately predict the flight path of a .22, the program should look like this (numbers for illustration purposes only):
0-75 yards: B.C. is .140
75 - 120 yds: B.C. is .130
120 - 200 yds: B.C. is .110
etc.
Bryan Litz's applied ballistics does allow the shooter to input data like this to get more accurate outputs, but I've never had the equipment to gather that kind of info, so again, I just let the bullet do the talking, and then try to trick the ballistic solvers into closely duplicating field data. (P.S. - When you do trick the ballistic computers into duplicating field data, jot down how you did it [i.e. what you had to change muzzle velocity and B.C. to], so you can do it in the field when conditions are different)
Here are some of my field results. Hopefully these numbers can help you find what you're looking for.
Test Rifle: Ruger 10/22 w/ Green Mountain .920" diam bull barrel. 17.5" length, 1/16" twist rate, stainless steel.
Condtions: Zeroed at 50 yds (in same conditions as testing was done). Temp: 45 deg. F; Altitude: 3100 ft. (Barometric Pressure, Density Altitude, and humidity unknown as I didn't have a kestrel at the time
Test Ammo: Remington Gold Bullet (Bulk 550 rnds/box)
Accuracy: ~ 2 MOA (This ammo likes warm weather and can shoot 1 MOA as far as 300 yards when the temp is 70 degrees or higher)
Muzzle Velocities: High: 1198 fps; Low: 1076 fps; Avg: 1145 fps
Drop (Inches)
75 yds -2.5"
100 yds -6"
125 yds -11"
150 yds -19.5"
175 yds -29.5"
200 yds -44.5"
225 yds -59"
250 yds -77"
275 yds -96"
300 yds -120"
Max Range:
Remington Gold Bullet will begin to tumble between 280 - 300 yards in the conditions described above. At that range, it is still adequately accurate to hit a milk jug and is usually 2 for 3 or better on Gatorade Bottles (the fat ones) if the shooter does everything right in 7-10 mph winds. Once the bullet begins to tumble, the wind will make it very unpredictable. However, if there is no wind (0 - 2.5 mph) the weapon can be employed accurately to 350 yds in these conditions.
With the temperature down in the teens (15 degrees F), the bullet exits the barrel substantially slower and has only been found effective out to 140 yds with light winds. After that, nothing good happens. Remington Gold Bullet is very temp sensitive (sorry, no M.V.s recorded yet)
In 98 degree days with high Tennessee humidity (98% easily) at 5,000 feet altitude; I've engaged IDPA targets at 500 yards with Remington Gold bullet. Drop at that distance was 480" (91.75 MOA). In a 5-7 mph wind, we were achieving 2 hits for every 5 shots.
In order to get a similar ballistic table out of my program, I have to set the Barometric Pressure to 25.75; B.C. of the bullet to .140 (G1 Scale) and muzzle velocity to 1190 fps. While I'm almost certain those values aren't correct, they get my calculator to match my field data, so who cares!?
Other interesting field data that you might find useful:
I've found that Winchester M-22 bulk ammo is more consistent at longer ranges than Remington Gold bullet, and only slightly more expensive. It has an average M.V. of 1255 fps and a B.C. of .145 in the same rifle as described above. The projectile is 40 gr. as opposed to the Remington Gold Bullet, which is 36 gr. Both ammos shoot the same zero at 50 yards.
Field Relative Zeroes:
If zeroed for Remington Gold Bullet and/or Winchester M-22 at 50 yds:
Blazer will hit about .75" low @ 50 yds. Ballistics are comparable to Remington Gold Bullet
Eley Tenex will hit 1.6" low @ 50 yds. It is subsonic, so I like to switch to it when I need to make a suppressed shot. It's also stupid accurate (.25 MOA), so I switch to it when somebody bets me I can't hit something at the range (won a couple bucks hitting flies and thumbtacks off the backboard at 50 yds this way). When they see you shooting Gold Bullet, make you a bet, and then you switch to Eley Tenex, adjust the rifle to new zero, and then hit the period at the end of their sentence, you've earned your prize!
GE American Eagle Match will hit 1" low @ 50 yds. It is also subsonic (not sure if they even make it any more) and groups about .6" @ 50 yards, so it's my intermediate match/suppressed ammo.
I sincerely hope that somebody finds all this useful, because that's about 3 years of field data in a nutshell.
