It's not all the same, metro.

A heavier arrow takes a bit more energy from the bow. Usually only 2-3 ft lbs, so it's not much, but it can make a big difference in how long your bow lasts. It's just that much less energy left for the bow to absorb, to cause extra noiseor to makescrews and boltsvibrate loose. I think a bit heavier arrow is more pleasant to shoot, because it's just that much less energy left in the bow to be transmitted to your hand. Or make you have to buy expensive rubber doodads to help absorb the vibration.

But as far as hunting bigger game goes, the heavier arrow not only takes a bit more energy from the bow, it also carries it's energy better downrange.Thehefty arrow hits the animalwith considerably more energy than a light arrow does, making for deeper penetration.

Dr. Ed Ashby has donelong term research on arrow lethality, first on large African game and is currently doing another study on Asian buffalo in Australia. He and I are in complete agreement that arrow momentum is a much better tool for predicting depth of penetration than KE is. Another school of thought is that KE is a better indicator. A heavier arrow from the same bow will carry more energy AND momentum though, so no matter which side of the fence you are on, the heavier arrow wins.

For thin-skinned medium size game, the light arrow has proven it is effective. Some guys have also done well on elk and such with their light arrows, but I believe they take unnecessary risks doing that. A bit of a bad hit, poor penetration, and they've got a wounded animal to track. A heavier arrow is good insurance because it will penetrate deeper in all circumstances.

I think a good parallel is with bass fishing. Some guyslike to fish for largemouth bass with ultralight tackle and have proven big fish 'can' be taken with 2-4 lb test line. But pro fishermen, who have to put fish in the boat to get a paycheck, use much stouter equipment. Guys who want to be sure they've got a bit extra oomph when the arrow hits, for better penetration on larger animals, they use heavier arrows.

Now, you 'can' ramp up momentum with speed as well. For example, a 350 gn arrow at 300 fps carries the same momentum as a 700 gn arrow at 150 fps.However,Dr. Ashby has concluded that all momentum is not the same either. He says momentum gained through arrow speed is not nearly as effective as the momentum gained through arrow weight. He's spent many years doing research in the field, on actual animalflesh and boneinstead of poking arrows into foam targets, so I tend to believe his results.

I believe a very old rule of thumb is just as valid as it was many years ago. For hunting, use the heaviest arrow that will give you acceptable trajectory. Don't use the heaviest arrow you can get. Don't go with the flattest trajectory you can get. Balance the two.

Archery has always a matter of trade offs - sacrificing one thing to get another. Contrary to popular belief among the speed cult,none of the technology that has come along has changed that, nor will it ever change that. They use ultra light arrows to get the fastest speed and flattest trajectory possible. What they trade for that is shorter bow life, more expense (those rubber doodads I mentioned earlier, for example), more bow noise... Not to mention having to buy a new bow every year or two just to stay on the raw edge of performance.

Whether that's smart or not, I'll leave it to you to be the judge.