If you want to experiment, try a gain twist from zero for a few inches in front of the chamber to whatever you need for stabilization at the muzzle.
Only one issue with this. If the grooves in the bullet start out straight (0 twist) and then the grooves change to angled grooves (say 1 turn in 10" for a 200 gr .30 cal) the grooves will end up tapered in the bullet (wider at the back of the bullet) and stability will suffer. Gain twists were popular with patched balls and soft lead bullets, but the amount of gain twist is minimal (ie from 1-30 to 1-26 twist). The lead or patch deformed enough to follow the rifling. Variations in twist rate up OR down over about 3/4" have been PROVEN detrimental to accuracy in benchrest barrels. That is why some benchrest shooters have a barrel scan done before wasting money threading and chambering to ensure consistent rifling.
BTW, Pac/Nor is in Brookings, OR (about 3 hours drive from my shop), and I have one of their polygon rifled stainless match barrels on my scratch-built 6ppc bolt action. I picked 1-10 twist so I could shoot heavier bullets for deer hunting (std for the PPC is 1-14 for 68 gr boat-tails). I have developed loads with H322 for 55gr Ballistic Tips, 70gr BTs, 90gr BTs and 95gr Partitions that ALL shoot consistently under 1/2" at 100 yds. One barrel doesn't prove anything positively, but if your twist is fast enough for your heaviest bullet, and the chamber work is perfect, generally accuracy will be at least varmint/ hunting good, but not benchrest good with all bullet weights. This combo has accounted for 2 3pt bucks, 2 does, a few rock chucks and innumerable sage rats. No deer has needed a 2nd shot with the Partitions, and the diggers positively EXPLODE with the 55gr ballistic tips.
Back on topic though, Pac/Nor's polygon barrels actually still have lands and grooves, but instead of sharp 90degree corners, the lands have angled sides. This does allow a little more velocity with lower engaving pressure, but you must help your cleaning rod follow the twist when you clean or the patch will just cruise straight down the barrel without turning
. Copper fouling is greatly reduced, though, as it tends to accumulate in the corners of conventional rifling. I have been pleased with this setup, and will probably replace it with the same when it wears out. As for number of grooves some cartridges seem to be picky, some don't. The .300 WSM was proven in early tests to strongly prefer 4 or 5 grooves to 6. The .30/06 seems to perform about the same from 2 grooves to 6. Your best bet is to talk to the guys making the barrels as they get LOTS of feedback if a particular twist or groove count is not working in a particular caliber. Google Pac/Nor for a phone number and Penney will put you through to whoever has the most experience in your caliber. Do them a favor, though and if they give you the info you need, ORDER ONE OF THEIR BARRELS. I am not affiliated with them other than as a customer, but there is nothing I hate worse as a business owner than someone who calls and picks my brain for an hour and then buys a gun at Whale-mart because it is 20 bucks cheaper
Hope this helps!
Tom