Straight rifling help

[u/inserttext1]

So I'm working on a fun project of making a 1911 shotshell platform, and I managed to score a completely blank, unrifled barrel, and there lies the biggest issue I have. As is, I cannot put it into a gun, as that would make it an AoW, which aren't legal in my state. Now obviously, if I put traditional spiral rifling on it, I would not only defeat the purpose of getting a completely blank barrel in the first place, but I would also negatively impact the spread of pellets. I have heard through some historical sources and a modern company that straight rifling not only wouldn't negatively impact shot spreading, it would also make it not an AoW anymore. So my question is there any modern company that does this type of rifling?

[u/Suspectgore074]

What tools/machines do you have?

[u/inserttext1 → u/Suspectgore074]

Lathe (not helpful), a 1 ton arbor press, and access to a mill

[u/Suspectgore074 → u/inserttext1]

You can make a square rifling bit with both the mill and the lathe, and press the rifling bit through your barrel with a press and tonnes of cutting oil/lube. You will want it to be piloted, so maybe a round leading edge to fit the bore followed by 4 slightly larger than bore diameter edges for rifling. You dont need alot, between .005" and .010" will be good enough.

I would probably run a couple test runs on similar diameter tubes before jumping straight into doing it on the real barrel, though.

Mark serbu did a video on something like this years ago

[u/TacTurtle → u/inserttext1]

Make a broach on the lathe (basically round stock with a couple cutter teeth in a line getting sequentially larger) and use the press to push the cutter through to make the rifling.

Alternatively you could make a single point cutter by cutting a slot in round stock for a HSS or carbide insert.

Example from the interwebs:

Remember, you don't need super deep rifling for straight rifling, just .002" is plenty.

[u/SteveHamlin1]

Modern company selling a straight-grooved firearm: https://franklinarmory.com/reformation/

(it's not rifling of any sort because it is not spiral)

[u/Neetbuxthor]

If you find a way to make extremely shallow (but still obviously there, for ATF compliance) and extremely slow twist rate rifling (for example, 1:66 or 1:72 or slower isnt unheard of for muzzle loaders) that would minimize the downside while staying technically legal.

I think the hard part would be actually forming or cutting the grooves. Maybe home builders or 3d printed firearm enthusiasts could chime in? I've heard talk of using electricity to erode rifling into blank barrels before, but never looked that deep into it.

Edit: I'd recommend you look into button rifling. This might be your solution, if you can make a custom rifling button with lathe/millwork, it just might work.

Edit2: This is the video that came to mind https://youtu.be/bJLnFXS1zxI?is=MIG4-HUk3XzKMWlW

Good luck!

[u/TacTurtle → u/Neetbuxthor]

Straight rifling using a broach.

[u/CleverHearts]

Unless it's a 410 you're making a DD. The exemption for >.5" bore only applies to shotguns and some rifles, not handguns. 

Rifling cutters are pretty easy to make. Look at the ones PTG sells to get an idea of what you need. You can use your lathe to cut the rifling, similar to broaching a keyway on a lathe. 

[u/TacTurtle]

Straight rifling works dandy for shotshells - TC Condenders were set up like this.

Typically this straight rifling would be done on a custom basis using a broach cutter pressed or pulled through the barrel or using EDM.