Glad Orion mentioned it! Have been experimenting on barreled cedar shaft and drilled out the nose to insert a nail, filled the hole with resin first.
Went from bare shaft of 546 to 680gn. Keeping it straight was the problem.
Also found this stuff called wood hardener my mate put me onto it when I was renovating dry rot in old window casements. I put a couple of coats on the shaft and hard, sealed and waterproof, really helps in the tropics.

Ive never done the nail thing but will try! Certain woods just are more porous and will absorb a given amount of oil and will gain a certain amount of weight! Other woods with higher resin contents wount hardly gain anything at all! Im interested to see what i end up with and how consistently each shaft absorbed the oil!

mnbear:  I may have misspoke.   Jim might be making reparrows in purple heart.  I only have one t home and it appears to be maple.  I have a few at my cabin that I remember being darker.  Thought they were cherry, but they may be purple heart.  He's also experimenting with POC now, but that won't add any weight.

Interesting that your Doug firs seem to be soaking up a lot of oil. Very interested in how much weight they gain.  Might want to wait longer than 4 days before sealing.  I found that mine often "bled" for longer than that, particularly if I soaked them under pressure.

I will take that into consideration! Ive always waited the same amount of days drying as i soaked them, kinda a rule i made! This time of year it shouldnt be a problem with the heat running! I always set the shafts in the register cuts in the register by the deck door! I leave the blinds open so i get alot of good sun on em plus the hot air from the furnace throughout the day!

Pulled my shafts out of the oil and let em dry for 4hrs and then i grabbed a few and they felt fairly dry so i thought whats the harm in doin a quick weight check! WOW!!! There shafts were all about 385-390gr when i weighed them before soaking! Now they are all between 460-470gr on my $20 digital scale i got from 3Rivers! Way more than i expected, but i know its early and they may lose a little! Checking em again tomorrow!

Just rechecked the weight and had to do a little hand straightening of my shafts but all in all they are turning out nice and im pleased! They all weigh in at about 460gr give or take a few grains! They are goin to be some good impalers for the longbow!

I soaked my Hildebrand (tappered 10" toward the nock )douglas firs in "Minwax Wood Hardener for 5 days topping off each day making sure they were always covered. It added about 35 to 37 grains to shaft weight. They finished off to 572 grains with 160 grain snuffers and also with 160 grain Magnus two blade broadheads. They are for a 56 LB Wes Walace Royal LB. I really like the way they shoot.I appreciate the modest weight gain but was motived  toward weather proofing the arrows.