I'm not sure where to post this. Legal, or smithing... But it makes more sense here. So I'll post it here and if the admins think it belongs in legal, please move it there.


You have to rifle a barrel that is less than 18 inches. (I think that has been changed to 16 inches now. But I am not sure of that.)

But is there a guideline that says what the rifling has to be? IOW: Does it have to be a certain depth? Does it HAVE to have a twist to it?

Vague description off ATF site:
"Spiral grooves in a gun`s bore that spin the projectile in flight and impart accuracy".
Probably depends more on whether the Chief, Firearms Technology Branch got laid the night before than anything else.

You know, this begs a question that never occurred to me before...

Why are they so concerned about accuracy?

I mean.. Seriously. What is the point in requiring rifling? If their own description is any indication of their intention, rifling is for accuracy. So they are in essence, requiring accuracy.

Is there anything there that says WHY they require rifling?

Do you have a link, so I can go read it myself?

One last... A twist of one in 48, is still a twist, even in a 6 inch barrel.

No rifling and a stock means it's a shotgun.
Under 18" barrel smoothbore is an NFA item, even if a pistol.

This is what other gun sites reference.
https://www.atf.gov/firearms/firearms-g ... tion-rifle

You could always ask the technology branch for a ruling or explanation.



https://www.gpo.gov/fdsys/pkg/USCODE-20 ... chap44.htm

I immediately though of the black powder pistols I've shot in Kentucky. Thought for sure they were smooth bore.

Looking these up I think you are on the right track. The first kit has a 1 in 30" twist.

http://www.possibleshop.com/pistol-kit.html

Thank you.

I am going to keep looking, to see if I can find whether the ATF requires a minimum amount of twist and/or depth of the rifling.

One guy with years of experience in home-building, told me that with the ATFs guidelines, a couple of scratches inside the barrel, qualifies. But he has usually done actual rifling, just to not invite trouble.

I'm hoping that something like 1/32" wide, 1/64" deep... and whatever twist amounts to, half the width of the rifling, from one end of the barrel to the other, will qualify. If so, I wouldn't mind making the tooling to do say 6 concentric grooves like that.

1 in 30 is 1/5 of an inch in 6 inches. That's still more than I wanted to do.

Why make it difficult? If one can look down the bore and SEE spiral grooves it's rifled. Depth doesn't really matter because some rifling is only .001-.002" in "depth" to begin with. Smooth bore means "smooth" (with the exception of corrosion and pits of course).

"When you hear hoof beats think Horses, not Zebra's".

As for barrel length, regardless of what some people might say, it's always measured from bolt face to end of barrel. Length can be increased by merely permanently attaching a flash suppressor, no rifling required.

I'm assuming you have a shotgun barrel that is 16"? you can permanently attach a break or something on it like deadshot2 said. as far as rifling it, it would still have to be 18" barrel for a shot gun. https://thefiringline.com/forums/showth ... p?t=358135 this link talks about it. and for depth of you land and grooves usually depends on the diameter of the bullet you will be shooting. The twist determines what grain bullet you can stabilize

Which is immaterial if "The LAW" sees any grooves or rifling at all in a shotgun barrel less than 18".

Not safe to assume, here. No, I don't have a shotgun barrel less than 16". Shortest shotgun barrel I have is 18 1/2 inches. Bought from cabellas.

What I was thinking about making is a .410 pistol. Probably single shot, break-barrel. Gotta find me a free .410 barrel, first. (Or a piece of one.)

I saw where someone made a revolving .410 shotgun, homemade. I'm still thinking pistol, so even if I attempted a revolver, I'd sill have to rifle the barrel.

might be easier to find a .45-70 barrel (.458") to cut down.