First, you can't compare penetration on steel to game. The 30 caliber armor piercing military bullet will penetrate tremendous depth in steel and the ball ammo will go through 2 feet of green oak but let me see you kill deer with them. We all know the .223 is a very bad choice on big game but the 30-30 is great. My 335 gr .45 colt LBT will go all the way through a deer from ass to neck at 1150 fps. The 320 gr LBT .44 bullet will go end to end in a cape buffalo at less then 1300 fps. How deep will your .223 go? Shot in the skull or leg bone and it will splatter to pieces. I have shot my 45-70 revolver with cast LBT's with a large flat meplat through 14" diameter trees at 1535 fps and it drops deer like they were struck by lightning. Slow, but heavy bullets! I have never recovered a heavy revolver bullet from any animal. But I recover every 240 gr jacketed bullet at a much higher velocity.
I have shot deer with all weights of arrows and with a crossbow with those short light bolts.
Your toothpick will kill just fine with a perfect chest shot but let all of us know what happens when the deer moves and you hit a big leg bone or the shoulder blade. My friend shot a deer in the spine last week with a carbon arrow and it only penetrated 1/8" into the spinal cord. Luckily it was just enough to paralyze it. I shot mine in the spine 2 days ago and the arrow was halfway through the deer. It was a small deer and the force knocked the deer sideways off it's feet which limited penetration. Had it been a heavy deer, the arrow would have gone all the way through.
You do state something I agree with and that is mechanical heads need energy to penetrate and that only comes with arrow weight.
One arrow I use weighs 605 grs and the other weighs 650 grs. My energy figures are 80 and 82 ft pounds respectivly. Would you care to try and stop one? I will put up mine to any of yours and we can see what is best.
By the way, the .223 hunting bullet will not go all the way through 1/2" steel, but the .220 swift will. Another bad choice for deer. The .223 shot into wood (not a board) will go in a very short distance. We are not talking about military ammo now as they are constructed to penetrate. VERY poor choice for hunting.
We must compare apples to apples here, NOT apples to grapes.

I tune my bow to A 442.

Excuse me, but could we get back to my original question, please?

Thanks,

Sorry, the "heavy aluminum arrow" sermon caused me to doubt that I was a real hunter. I use toothpicks.

Take a 30/30 Win vs. a 223 on a 1/2 inch of plate steel... and the "WEIGHT NOT SPEED" theorum goes right out the window.

Take a 100 grain mechanical and a 100 grain fixed on a 1 inch board... and the "WEIGHT NOT SPEED" theorum goes right out the window.

Weight isn't the only factor we're looking at here, obviously.

As Derf mentioned: mechanicals require more KE to operate reliably. Something like 55 foot pounds is recommended for mechanicals. Most of today's bows produce 60 or better, so you're probably good as far as that goes, but the bottom line is that you need more energy over a fixed head.

If you need more weight to make up for the mechanical head, then you're probably better served by just going to a fixed broadhead of the same weight, rather than tailoring the arrow with another component. You'll keep it simple, you'll spend less per arrow, and probably get the type of penetration you're looking for.

Some mechanicals have ridiculous cutting diameters. I don't know what your diameter is, but like I said earlier, all those expanding wings do reliably is help slow down the arrow when it hits something. Ergo, the minimum KE requirements.

You can probably tell that I don't like mechanicals. The simple fact is that it's easier to push a real pointy object through something than it is to push an object with more surface through something.

IMO, if penetration is an issue, then I wouldn't even consider a mechanical. Why complicate things?

You need to keep your Front of Center Balance (FOC) within somewhat close proximity for optimal Arrow Flight.

Here is a link that should explain it.

I'd take that action, bfrshooter. I think you'd be surprised that there is more than one solution to the problem. I'm pushing more than 420 grains at 280 FPS which puts me in the 70ish foot pound range. That's plenty. I'm a big guy, I can pull monster poundage bows, and I've blown through enough spines... and boards in my back fence to doubt that you'd see any appreciable penetration difference with your heavy arrow over mine.

I stalk deer primarily. That translates to lots of shots on semi-alert animals. I'll take the flatter trajectory of my arrow every time.