Well, I was curious, too, so I ordered 50 3/8" birch dowels from American Woodcrafters. They are all straight, 36" long, and look like they would make decent arrows. Some grain runout, and a few knots here and there, but for the most part they appear to be serviceable. Out of the 50, here's how they spined out:
68-1 70-1 73-2 75-3 76-2 79-1 81-1 84-1 87-7 90-2 93-4 96-7 98-1 100-5 104-8 108-3 130-1

Those are WAY heavier than I thought they would be, but I wanted to see for myself.

The 5/16" I have used in the past maxed out at 55#, with the majority going in the low to mid 40's.

Just thought you'd like to know.

I've been curious about that, thanks.

I use 5/16 Dowels, and "Perfect" they arent, but I have had a Lot of Fun Building them and Shooting them. "Frugality" is just another Word for "Cheap, but Good"!!
Oh, I shoot either a 45# LongBow, Or 50# Recurves!

I performed an experiment last night with one of the stiffest shafts in the bunch. I took a 108# shaft (!) and straightened it, then tapered the shaft to 5/16 at the rear, and made a self nock. Then I cut the shaft to 32" and installed a 160 grain point. (You can tell we're still snowed in here in Denver).

Surprise, surprise! The thing bareshafted great from my 52# Pronghorn! Of course, that's in the basement, but still...

At 32" and 770 grains, you won't win any flight shooting contests, but it's a viable arrow, at any rate.

I'm curious what would happen if you took them down to 11/32.  How much spine would you lose?  Also, doesn't shortening an arrow increase spine? curious?!?!

Shortening an arrow increases dynamic spine. That is, it acts stiffer, but the actual spine doesn't increase. It's the same stick. I guesstimated 32" mainly because I didn't want to fool with a 36" arrow, LOL! You can reduce spine considerably by decreasing it's diameter, but I haven't done it.

Good info, thanx.
Does anyone know how ramin compares with birch?

I believe it's heavier, but it's becoming hard to get in the U.S. It's not imported any more due to environmental concerns.