A few things to consider:
The farther the range the better the drag coefficient (Cd) and ballistic coefficient (bc) need to be in order to sustain velocity and so the amount of energy required at point of impact (poi).
The stronger the winds the better the Cd and bc should be to counter wind drift and head wind pressure.
The slower the muzzle velocity below that at which best accuracy/precision is achieved for the rifle/pellet combination the greater is the wind influence; and the the more critical is the sight/holdover adjustment required for precision shooting.
The more powerful the rifle/ pellet combination, the more critical it is for the shooter's skills to hold together especially during triggering and follow - through.
These factors, though not all inclusive, become increasingly significant when seeking accuracy and poa/poi coincidence at increasing range especially under adverse environmental influences.
The best ballistic coefficients, for the best pellets in the smaller calibres, that I have measured from my rifles run something like this for "average" conditions at my farm but summer/ winter need tweeking.
.177 - 0.028 for 13.43 gr JSB Monsters and .09 Prometheus Piledrivers.
.22 - 0.034 for JSB 18.1 gr Exact Heavies; 0.048 for new Revised 25.4 gr Monster JSB; 0.08 for Prometheus 30 gr Piledrivers.
.25 - 0.05+ for JSB 33.9 gr King Heavies Mk 1 ; 0.038 for normal 25.4 gr Kings JSB.
All my rifles are super accurate for that for which they are designed. All are run at the optimal mv for the above pellets.
So, with the above points of consideration in mind, I have a sound base for deciding which calibre and which pellets may be best for the job at hand.
This morning at our farm it was a little breezy and as it is rather open grazing land, I took the .25 FX Crown and a magazine of 33.9 gr JSB King Heavies Mk 1 skirt sized to 0.2515" (to easily load the magazine) and lubricated with a wax. Shooting at 850 fps, which I have found to be in the middle of the best Cd and accuracy range using the LabRadar, I took a stroll - walk a little, look a lot- and enjoyed the early morning crisp autumn air. Three shots, one at 87 yd from a tree branch lean; a second at 48 yd also from a tree branch; and a third also head shot at 131 yd off the top of a fence strainer post was a very satisfactory morning. The last was waited out for a lull in the movement of the grass. No hurry, the bunny was warming itself in the early morning sun. I use an old Bushnell rangefinder and Chairgun calibrated for my 3,640 ft altitude and prevailing temperature.
The Crown has now shot 219 rabbits off this property when we have visited since December. They are pretty much back under control now.
Life is good. I hope some of the newer shooters may get something to think through from this.
Best regards to all, Harry in OZ.
The farther the range the better the drag coefficient (Cd) and ballistic coefficient (bc) need to be in order to sustain velocity and so the amount of energy required at point of impact (poi).
The stronger the winds the better the Cd and bc should be to counter wind drift and head wind pressure.
The slower the muzzle velocity below that at which best accuracy/precision is achieved for the rifle/pellet combination the greater is the wind influence; and the the more critical is the sight/holdover adjustment required for precision shooting.
The more powerful the rifle/ pellet combination, the more critical it is for the shooter's skills to hold together especially during triggering and follow - through.
These factors, though not all inclusive, become increasingly significant when seeking accuracy and poa/poi coincidence at increasing range especially under adverse environmental influences.
The best ballistic coefficients, for the best pellets in the smaller calibres, that I have measured from my rifles run something like this for "average" conditions at my farm but summer/ winter need tweeking.
.177 - 0.028 for 13.43 gr JSB Monsters and .09 Prometheus Piledrivers.
.22 - 0.034 for JSB 18.1 gr Exact Heavies; 0.048 for new Revised 25.4 gr Monster JSB; 0.08 for Prometheus 30 gr Piledrivers.
.25 - 0.05+ for JSB 33.9 gr King Heavies Mk 1 ; 0.038 for normal 25.4 gr Kings JSB.
All my rifles are super accurate for that for which they are designed. All are run at the optimal mv for the above pellets.
So, with the above points of consideration in mind, I have a sound base for deciding which calibre and which pellets may be best for the job at hand.
This morning at our farm it was a little breezy and as it is rather open grazing land, I took the .25 FX Crown and a magazine of 33.9 gr JSB King Heavies Mk 1 skirt sized to 0.2515" (to easily load the magazine) and lubricated with a wax. Shooting at 850 fps, which I have found to be in the middle of the best Cd and accuracy range using the LabRadar, I took a stroll - walk a little, look a lot- and enjoyed the early morning crisp autumn air. Three shots, one at 87 yd from a tree branch lean; a second at 48 yd also from a tree branch; and a third also head shot at 131 yd off the top of a fence strainer post was a very satisfactory morning. The last was waited out for a lull in the movement of the grass. No hurry, the bunny was warming itself in the early morning sun. I use an old Bushnell rangefinder and Chairgun calibrated for my 3,640 ft altitude and prevailing temperature.
The Crown has now shot 219 rabbits off this property when we have visited since December. They are pretty much back under control now.
Life is good. I hope some of the newer shooters may get something to think through from this.
Best regards to all, Harry in OZ.
