Enlarging a barrel channel at home without a mill is as simple as a wooden dowel of correct diameter with 60 grit sand paper wrapped around it. A bit of elbow grease with alot of checking the fit. Or you could just have a gunsmith do it for a few bucks as mentioned above while you enjoy your time otherwise. Good luck.
I don't have generic barrel channel programs. I generate each one individually. This means you will need to take some #s for me if you don't send the whole gun. 2nd. My channels are true surface models. Not a series of linear passes with a router. Does the gun care or shoot better because of this? Absolutely not. I do it cause in my opinion it looks better. Much better.
As stated above, they are "made to order" . A basic design does NOT mean a perfect fit. We require the barrel to match the fit. Happy sanding as it IS satisfying to do it yourself.