When you don’t have 100 yards or metres to zero your hunting rifle, the short range alternative is a good fallback.
It’s been a while since I have had reliable access to a 100 metre range to zero and accuracy test my hunting rifles and, being an experimental kind of shooter who likes versatility for different hunting needs, I was a little miffed. Nevertheless, there is no problem that cannot be solved with basic resources and a bit of applied commonsense. So, where to start.
One of the best tools I use is the Sierra Infinity 6 Ballistics program. Applying some commonsense and realising that I had regular access to a 50 metre range, I fed Infinity the data for three of my loads: .30-06 165gn Spitzer, .308 150gn Spitzer and .270Win. 130gn Spitzer, all boattails. Wanting a maximum point blank range (MPBR)effective zero, I hit the MPBR tab on the program and computed the trajectory in 50 metre increments out to 500metres and – bingo – the results were displayed.
Commonsense borne of previous ballistic experimentation told me that with a MPBR zero with most standard medium to big game cartridges (not hot-shot magnums) holdovers out to 500 metres were within 6-inches with weight-appropriate bullets for each cartridge (like a 100gn .243, 130gn .270 and 165gn .30-06 for example).
So what did Sierra tell me about a 50 metre MPBR zero?
For the 150gn .308 doing 2800fps I should zero 1.5 inches high at 50 metres. For the 130gn 270 Win. At 3,000fps zero 1.4 inches high and for the 165gn .30-06 at 2750fps, zero 1.6 inches high.
Now with the vagaries of altitude, temperature and other factors like less-than ideal hold and trigger release in the field, you can pretty confidently zero your standard medium-big game rifle an inch and a half high at 50 metres and you won’t go far wrong.
You may ask, “Did you field test this zero?” and I can say that I did so not long ago. With my M17 .308 (150gn load) I shot half a dozen fallow from 170 to 370 metres over four days and they all died quickly, hit where I expected them to be hit from a solid prone rested position. More recently, I zeroed a factory 180gn round-nose RWS load 1.7 inches high (bit of commonsense plus .2-inch allowance added for a heavier than standard bullet) at 50 metres and bagged a trophy red stag at 180 metres and it hit right where I aimed off a wobbly offhand shot.
When it comes right down to it, .2 of an inch multiplied six times to take it out to 300 metres only alters your impact point by 1.2 inches, so if you standardised on a 1.5 inch high 50 metre zero for any of a number of standard centrefire loadings in the 2600-3000fps range you’ll be hard pressed to notice any errors when hunting with it.
MARCUS O’DEAN
Editor
Caption: This fallow buck shot at 370 metres didn’t know at what range I zeroed my .308, nor do I think he cared.
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