thats not a bad idea, I've thought about doing that actually and even experimented a little with it,alumin arrow's ID varies with wall thickness(which is more than likely why you had trouble geting those 20/64 arrows inside those 2216's), and from what I've foundalumin. arrow'sIDalso varies from carbon arrows
I have looked in my books before and found that there are a number of bullets that should theoritically work in a number of different arrows, I cant remember any of them now but all ittakes is a dial caliper to measure the arrows ID and a bulletreference guide to figure out what dia bullet would fit the arrow best...
anidea I had along the same line was making my own plugs to fit behind the insert, however theres a few things that didnt really appeal to me with going that route, or the bullet route, or even with the screw-in weights


one is the fact that with that approach the weight is behind the insert and the fartherinward from the tip of the arrow the weight is the less effect it has on FOC, too far in and all it becomes is dead weight, the inserts in my thunderbolts are already an 1-1/4" long, which would put the plug at around 1-1/4" to probably 2" in from the end of the arrow, which in my case would be around 4" in from the tip of the arrowspoint(broadhead), which with a 22" total length arrowwith an 11" centeritsclosing in fast on what the actual balance point would be in calculating FOC...
my arrow weight is good enough, I dont reallywant toadd any unnecessary weight, so all the weight I add or moveI'd like to be as far forward as possible to be as efficient as possible in improving FOC, making brass washers to put between the tip and insert is one idea I had which would put the weight in front of the insert, however with the size limitation of doing that your kind of limited as to how much weight thewasher can be, your also increasing the total length of the arrow(not that that little bit would really matter)

I run inserts for nocksbecause I need them for my fletching jig(I made an adapter for my fletching jig that screws into the insert and then locks into my jig),the insertsweigh 43gr but Ifound that I can cut them down without any effect on my adapter, from the little bit I've experimented I cancut well over 20gr off of them, which would drop the inserts weight to around 20gr,probably less,that will have an fairly big impact on shifting weight without adding any I think, sothats on my list of things to try(and probablyre-do)...



another thing that doesnt appeal to me is the fact that I dont really like or trustthe idea of a plug being just glued inside the shaft, even with epoxy I just wouldnt trust that it would hold in place and would have to have it screwed into the back of the insert somehow anyway, which would require a fair ammount of fab work to get everything the same and equal in a dozen arrows, besides the fact of getting it back out if I decided I didnt like it in there...


which brings me to the next reason it doesnt really appeal to me(or alot of the other ideas)... and that is the fact thatI like to tinker with the best of them, but I'm notdumb, andI see it as kind of pointless to go through all the elaborate work and messing around to make something custom work to add or move weightto the front of the arrowwhen I can just buy the more effecient brass inserts and be done with it...

which is also on the list...