Re: Max EFFECTIVE Range for 243 on antelope...
It basically comes down to how far YOU can put your bullets consistantly into an 8" diameter group.
The 243 with most bullets will kill an pronghorn out to any range you can hit it in the vitals. As BB has correctly mentioned, not all 6mm bullets are created equal. Some will fall on their face at 500 yards, others will reach out well past 1000 yards with a good head of steam left.
For the longest range shooting, I would say a fast twist barrel shooting the 105 gr Berger, 105 gr A-Max or 115 gr Bergers would be the best combination. Why not the 107 gr SMK, well, it will certainly work well but pronghorns are very thin critters, the SMK has a pretty heavy jacket in comparision and at longer ranges, the velocity will be quite low. You want quick expansion on a pronghorn so the thinner jacketed berger will expand better at longer ranges.
The tipped A-Max will also expand more quickly to offer better terminal damage to the vitals. Again, the 107 gr SMK will certainly work well but expect the goats to run a bit farther then with the softer bullets after impact. Not a big deal, where are they going to run to but it is something to consider.
I have shot rockchucks at 1000 yards with the 6mm-284 with both the 107 gr SMK and the 105 gr A-Max and while I can drive the 107 gr much faster because of its heavier jacket, on target, generally its not much more then a through and through hole in the chuck. With the A-Max, again, its started slower but it expands easier and more dramatically so the terminal results are more violent.
Pronghorns hurt easily. If you get a bullet on center of mass ahead of the liver, in most every case, you will get your goat if your smart. Blow a leg off and they can run for miles and miles but get into the vitals at all and they will generally die pretty quickly. As such a pin hole through the lungs will certainly kill a goat relatively quickly. More expansion will do even more damage.
In the 243, the A-Max, Berger and SMK can all be loaded to the same top velocity as it will not run them over the velocoty ceiling the A-Max and Bergers like so that should not be a real issue.
Simply put, with that combo, the determining factor is how far you can hit your mark with your rifle in field conditions.
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