What precision is possible at long range with an air rifle .. How does group size degrade with increasind distance?
Below are the current best figures I have for c-t-c 5 shot groups at the indicated ranges. They have been shot with ( Edit ) RWS Excalibre at 50 yd, and BSA Hornet ( 100, 150, 183 yd ) using JSB Exact 0.22 cal 15.9 gr pellets, MV 870 fps ( Excalibre ) fps 26.7 fpe; MV 900 fps ( BSA Hornet ) 28.6 fpe :
Data to date ( Edit: upgraded March '08 ) for the best 5 shot groups at each range:
50 yards - 0.344 MOA ( 0.18 inch / 4.57 mm ) Edit: 0.286 MOA, ( 0.15 inch, 3.70 mm )
100 yards - 0.525 MOA ( 0.55 inch / 13.97 mm ) Edit: 0.429 MOA, ( 0.45 inch, 11.43 mm )
150 yards - 0.764 MOA ( 1.20 inches / 30.48 mm )
183 yards - 1.148 MOA ( 2.20 inches / 55.88 mm ) Edit: 0.756 MOA, ( 1.45 inch, 36.83 mm )
Graphs: Data points are those actually shot with the above mentioned rifles and pellets:
# 1. Minute of angle for C-T-C 5 shot groups versus range in yards. Sorry my programme won't insert a least squares interpolation line, but you may guess any MOA / range correlation by eyeballing. For example, what is the furthest range that a 5 shot group of 1 MOA may be shot? Find 1 MOA in the vertical axis and go across and down to the horizontal axis to intersect at predicted approximately 175 yards. ( 1 MOA is 0.5235" at 50 yd; 1.047" at 100 yd; 1.57" at 150 yd; 2.094" at 200 yd. )
Edit March '08 -- Note that the most recent benchmarks for 50, 100 and 183 yards have not yet been inserted in this graph.
# 2. C-T-C 5 shot groups in inches versus range in yards.
# 3. C-T-C 5 shot groups in millimeters versus range in yards.
Discussion:
The relevance is that it is a window into the possible extreme of probability for the small .22 cal PCPs and best matching pellets based on best groups to date with the above rifles.
It may also give some estimate as to the relative degrading of precision over the bracketed ranges. The question is often asked as to what a group of a certain size at say 50 yards may have expanded to at longer range, say at 100 yards. In the above actual best case scenario it may be that the answer in this case would be approximately 3 times as big ( 0.55 / 0.18 = 3.055 ).
When graphed, it may allow for comparison of best possible group size at any intermediate range. ( 1.0" at 140 yards in the example graph above ).
Wendy and I have recently returned from 2 1/2 months in the Top End fishing and the rest spent in the Red Centre. We drove the Strzelecki Track from Lyndhurst to Cameron Corner and came home via Tibooburra, Broken Hill, Bourke, The Warrumbungles and the farm at Kentucky South out of Uralla .... Great trip in the new VW T5 Diesel Kombi AWD campervan. Fuel consumption averaged 8 L /100 km or 12.5 km / L .
Hope some of you find this of interest and please feel free to comment and to ask questions..... Kind regards, Yrrah.
). I would like to get the original back working as it is a pain changing adapters when using the two different rifles.
........ H.
....... 30 years from now when I am 100, you will be 8/10s. I wonder if I will still be using the old FX pump then, maybe not 
