TFOX, you never heard of Snuffer broadheads or Wensel Woodsmans, I guess. Muzzy broadheads were designed by a traditional shooter. I've still got a couple packs of old 160 gn Muzzy Matadors in my box. A lot of traditionalists use 3-blade heads. I guess most don't for the same reason I don't. I can't get cut on contact 3-bladers as sharp as I like for hunting. Another reason I use 2-blade heads is I can get a half dozen for $20 instead of 3 for $30, and they do a perfectly good job.

Now, the guys shooting lighter draw weights (<50 pounds), yeah, most of 'em use 2-blade heads and better penetration is the primary reason. They don't have much KE or momentum to work with.

As far as speed and friction, you are totally incorrect. It's a plain fact that the faster something is moving, the more friction is generated. It's inescapable. Your physics problem about moving the block along the table and it getting easier to move as it speeds up, that is the concept of applying force to overcome inertia and generate velocity. It does not take friction into account.

Say a Piper Cub plane is flying along at 100 mph. Wind resistance (air friction) won't hardly warm it's skin. An SR71 Blackbird flying in excess of Mach 3, it's skin will heat up to over 1200 degrees. It's an exaggerated example, for sure, but I use it to illustrate the point. Increased speed, increased friction.

Ever heard of the term 'terminal velocity'? It's the fastest rate something can fall. It happens when an object's speed increases just to the point where wind resistance (friction) is equal to the object's weight. It can't fall any faster because the air won't let it.

Wind resistance is why all arrows lose speed, energy and momentum between the bow and the target. Assuming all else is equal except arrow weight... A lighter and faster arrow will leave the bow with more velocity but less KE and momentum than the heavier arrow. It will expend a greater percentage of it's velocity, KE and momentum while traveling between the bow and the deer than the heavier, slower arrow will. Reason is the faster the arrow is going, the greater the wind resistance. The greater the wind resistance, the more energy it has to spend just cutting through the air. It will have less KE and momentum when it begins penetrating the hide of the animal. Because of it's speed, it will encounter a greater percentage of resistance from the animals tissues than the heavier arrow will. All of which means it will not penetrate as deeply. Again, all else being equal.

Back in my field archery days, I found I actually had better long range trajectory on the 60, 70 and 80 yard targets with heavier 2216's than I did with 2213's, but slightly better short range trajectory (40 yards and under) with the 2213's. There was right at 100 grains difference in arrow weight between those two and, with the lighter tips on the 2213's, they had practically the exact same FOC. The 2216's simply carried better downrange.

You know how I feel about testing penetration in foam and thinking the results would be the same in flesh. Completely different media so they cannot be directly correlated. But let's run with that for a bit. Generally, when you talk faster arrows, you're talking carbon vs aluminum. So, you're almost always talking a smaller diameter. Smaller diameter = less surface area = less friction. In a target that stops arrows by friction, heck yes the smaller diameter arrow is going to penetrate deeper. But, why have they come out with easy pull targets? Why have so many 3D shooters been forced to carry heavy duty arrow pullers and arrow lubricants on their quiver belts? Because all that excess friction generates heat and melts those little carbons into the targets and they're hell to pull!

Would the smaller diameter help offset some of the friction on the shaft caused by the higher speed? According to Dr. Ashby's research, yes. It does. But still, as I mentioned before, it's the broadhead that bears the brunt of the resistance during penetration.

Now, comparing the penetration - in styrofoam blocks thick enough to keep the arrows from coming out the backside - between my unweighted Gold Tips at 460 grains and the ones I've weighted up to over 700 grains (from my compound, since my draw length varies from shot to shot with my stickbows, which would vary KE and Momentum from shot to shot), the heavy ones do penetrate about 2" deeper. When you compare apples to apples, things don't work out to fit your preconceptions. I wish I could get broadheads to fly good enough with my carbon arrows to compare broadhead penetration in foam with my regular and weighted arrows. Unfortunately, they won't fly straight with broadheads. But penetration in foam is all some people tend to believe.

Actually, weight (mass) is THE OTHER factor used in both ke and momentum formulas. Surely you didn't think I'd let you slide on that'n, didja?

But, yes, increasing speed of a specific arrow will help, because it increases both ke and momentum, ke more than momentum because speed is squared in the formula. On the other hand, speed can also cause problems since it also increases friction and resistance. But then, when you're talking about shooting the same bow without increasing draw weight, speeding up the arrow means going lighter in arrow weight. Which, in turn, reduces KE, reduces momentum and increases resistance. Three strikes against it.

But, to let you off the hook, most guys these days are shooting enough poundage to generate gobs of KE (and momentum by default) to blow through deer on well placed broadside shots, in spite of their light arrows. IN SPITE OF, not because of. Like I said earlier, most of them are getting more energy from their little twigs than old time bowhunters were using to take elephants. Elephant bows for deer! It's the equivalent of loading a .458 Winchester mag with 150 gn bullets for deer hunting. Sure it would work - well, assuming the rifling could stabilize such a short, light bullet - but the beating you'd take from that monster! Anyway, I'm not worried about those guys. I just hope they're smart enough to use heavier arrows if they go after bigger game. Even rifle hunters use heavier bullets designed with thicker jackets for moose than they do for deer, for the same reason - better penetration

It's the folks who are NOT shooting high poundage bows and are not generating gobs of KE that I'm trying to get through to. IMO, they need to follow Cougar Mag's lead and use proportionally heavier arrows. Not just for simplicity's sake though. They actually need to, in order to maxmize their KE and momentum.