OK guys here’s the givens; I have a Winder Lowall, good tight action. Barrel, Chro-Mo .22 RF, 1:16” and 4 groove ratchet rifling. It will be a serious 100 yd. Benchrest comp. gun for matches with exposed hammer, a rule requirement. All things being equal it come down to accuracy and aesthetics.  Barrel will be around 22” to 24” depending on the bore size. I would like a octagon barrel because I think they look cool but don’t want to give up accuracy, so here is the question. For sake of discussion if I have a round barrel that measures .900” diameter at the muzzle and an octagon barrel of the same length and it measures.900” across the flats it will be the stiffer of the two, but, will it be inherently less accurate because it is octagon?
Thank you,
Richard

If your aesthetics statement is for real, make it longer= say 28'' or over inches. Just sayin'

When I am having benchrest barrels fit in the past I have asked the smiths to put the barrel between centers and take off just enough stock to true it and remove any scale / milling marks and thats it. 
Haveing said that my CPA / 49 has a #3 octagon barrel on it and it is supremely accurate. so if you got it in your head you want an octagon barrel go for it. 
Ya pays your money ya takes your chances.

40 Rod

Thanks for sharing that Ken. 
I have pretty much always shot a 1/2 Octagon to Round 28 inch #3 Steven's weight Douglas barrel off the bench and I still do so. 
I have bought all of my blanks from Gail at CPA and the last three were all pre-profiled and polished blanks. And Her pricing has alway been well beyond being fair. 
And the barrels themselves have all been absolute Jewels as received and they can actually be rust blued without any need for any additional work other than de-greasing.

Amoretti I have personally found that if one has an extremely competitive barrel. If it is round, half octagon to round or a full octagon that no matter how long it is or the actual barrel size. It will easily out perform the one who is actually behind it including the best Benchrest shooters in this Country and or those outside of it.

I want to thank all who have replied. From what I have gleaned so far, at least with .22 RF barrels and maybe all rifles using lead bullets is to make sure that the muzzle winds up at the tightest part of the bore. So I will definitely be slugging the bore before and after profiling it to octagon to find out what the bore contour looks like and go from there. Lapping if necessary.
Thanks guys
Richard

My general purpose barrel stub. 
First use it to apply pressure to the breech block to lap the breech block shoulders to assure uniform contact.
Next use it to lap the face of the breech block to assure it is perpendicular to the bore.
Usually less than .001" material removed. Not sure it is required, but makes me feel better.
Chuck

Not sure I understand the question.
The front of the receiver is faced off in the same setup used to thread the receiver. This becomes the "X" axis reference for all other cuts on the receiver.
The barrel stub shank is cut concentric with the threads and a known diameter. This becomes the "Y" axis reference for all other cuts on the receiver.
The barrel stub shank also establishes the "Z" axis.
If the barrel is threaded concentric to the bore, everything should come out pretty close.
Chuck