I am sure that you will get a lot of input saying that you are shooting plenty of weight, and for a perfectly placed shot you probably are. The problem is that a less than perfect shot or even a shot with fairly light bone, like a rib, can be enough to severely limit your set up. I have killed my fair share of game animals with a bow. Well over a hundred have fallen to my longbows or recurves. I have also shot animals with various arrow weights and head designs. Early on I realized that light weight arrows severely limited penetration. Mechanical heads cut big holes, but limited penetration even more. Even fixed blades without a cutting edge hurt penetration, and were nearly useless on heavy bone.
I have never shot an elk, but have shot a half dozen kudu as well as oryx and other large plains game species noted for being very tough. The lightest set up I used on game of that size was 600 grains with a big cut on contact head. Penetration was excellent without exception.
Those that know me, or have heard me rant in the past, know that I put a lot of stock in Dr. Ed Ashby's huge database of arrow penetration studies. There are a lot of take home points in the volumes of information he has accumulated. All of it is not necessary for elk sized game with decent shots, but there are a few take home points to me.
First, penetration increases linearly with increased arrow weight. The more weight, the better penetration...period. Now, there is a point at which weight becomes impractical. If it were me, I would push your weight closer to 500 grains, and practice, practice, practice. Range finders and sighted bows make drops in distance less of a factor when you know the distance. Secondly, use a cut on contact head with a STURDY point that won't curl upon impact. Any tip curl will dramatically reduce penetration. If you want to take it up another notch, go with a single bevel head beveled to match your fletchings (left bevel for left wing or left offset).
As far as brass inserts, I have used them. It is an easy way to add weight and to increase the forward of center (FOC) on your arrow, which is a good thing. The only down side is that it may weaken the spine of your arrow to the point that it doesn't fly as well from your bow.
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