Weight Tubes – I have not used weight tubes myself, but I would expect that they don’t affect spine or FOC too much (assuming they are installed full length inside arrow). Thus they add weight and increase penetration.

Brass Inserts – Stronger than aluminum ones that came with arrows and moves the center of gravity toward the front of the arrow.

Arrow Weight – Try to shoot at least 10 grains/pound on your bow. Thus, if you have a 50 pound bow, shoot at least 500 grain arrows. You will find your bow shoots more quietly with less vibration. My current setup uses a 14.5 grain per pound arrow. Thus I am shooting 800 grain arrow out of a 55 lb bow. Maybe a bit extreme. But that’s how it worked out with the abowyer broadhead, steel broadhead insert, and brass arrow insert. I still get about 160 fps.

All this said, if you use brass inserts and increase arrow weight, you may need to trim your arrow shafts to get good bare shaft flight. If you use tubes, probably a good idea to bare shaft tune just in case…

Maybe mess with your old arrows to see what happens. Then if you need more spine, you can return your Christmas arrows and get higher spined ones…

BTW – Thanks for taking my post about question marks so well… You are a big man 🙂

Generally speaking, I don’t mess around with switching arrows and the like during hunting season. I used to do that in the past and always ended up regretting it.

I am not sure, but I think maybe you are confusing grains per inch of arrow weight with grains per pound of bow weight.

When you are talking about “MFX Classics are 12” that’s grains per inch of arrow weight. What I was referring to is grains per pound of bow weight. In general, you should shoot no less than 10 grains per pound of bow weight for a hunting setup. Thus with your 55 lb bow, you should try to have at least a 550 grain arrow.

This is not written in stone, just a commonly held standard.

Grains per Inch – describes the weight of an arrow to its length. For example to find the GPI of a 30 inch arrow shaft that weights 300 grains you would divide 300 by 30 to arrive at 10 grains per inch.

Grains per Pound – describes the weight of an arrow to the draw weight of the bow used to shoot it. Most bow manufacturers will specify a minimum GPP arrow that can be used without violating their warranty limits. So If a manufacturer said you must shoot at least 8 grains per pound for them to honor the warranty, then you would multiply 8 by the weight of your bow. So if you had a 50lb bow, you would multiply 50 times 8 to arrive at 400 grains. This would be the minimum arrow weight you can shoot to maintain warranty. You can always go higher…

Hope this helps.