This is talking about using striking as contrasted with draw filing for barrel prep.
Here are some photos of a Colerain barrel. (These photos are from 2023, but the barrel is from old stock, maybe 15 or 20 years old, so I have no idea what Colerain's newer barrels look like. So please don't assume from these photos that they are all like this.)
I draw filed a few flats on this barrel, but when sighting along the length while holding it up to a light, I realized that it had a lot of ripples in it. So I switched to striking for the rest of the prep. For draw filing you hold the file perpendicular to the axis of the barrel. In contrast, for striking you hold the file in line with the axis of the barrel.
I used a wide tip permanent marker to black the surfaces. You can see the ripples very easily after a stroke of the file. I think it took about 20 minutes per flat to clean it up. Cleaned up perfectly fine.
As you can see in the next photo, the file I used was a 6 inch double cut. I ground off both ends and sloped the surfaces of the ends so that they had a slight "sled runner" profile. I also rounded the corners just a bit, for safety.
I use a lot of chalk to keep the teeth from filling when I do this. This is just school chalk rubbed into the teeth of the file. For the most part it, to clean the file I just run my thumb over the file to remove built up filings. If it gets bad, I knock a corner of the file against a block of steel (a blacksmithing tool) that I have sitting on the bench top. It occasionally required a file card. But in general, if using chalk, I try to just use my thumb, so as to keep the dust down. I put an old cookie sheet from the kitchen under the barrel to catch most of the filings and dust. I also use a dust mask, and
always wear eye protection in the shop.
Striking is hard on the hands. Helps to wrap the fingertips in cloth tape. Good to take a break after each flat, as well, to rest your wrists.
I talked with a friend about how he does this. He does the same task with a hand-held belt sander, but he has also done a lot of barrels and has gotten good at it. I don't have confidence that I could control a sander. Of course, compared to a sander, the file is slow, but very easy to control. And "slow" is relative. I don't think of 2-3 hours shop time on this as a being too long.
To date I've prepped three of these old Colerain B weight barrels this way. All three were pretty rough on the outside, and I found that the widths of the barrels were not all exactly the same. If you will be cutting your own barrel channel then that does not matter at all, but I'd recommend you clean up at least the three bottom flats and side flats of the barrel first, then cut the channel. If you will have someone else cut the channel for you, then I'd suggest you clean up the barrel first and have the channel cut to fit the particular barrel you will use. Don't assume that it will work out well for them to just use a similar barrel that they may have on hand. There may be quite a bit of variation between a rough barrel they have on hand and the cleaned-up barrel you intend to use.
