Filing a round barrel to octagon

[Camerl2009]

I’m looking at making a little .22 flintlock I have a take off barrel from an off topic gun that I’d like to build into a little small game rifle.

The barrel I have is tapered about 11/16 to 5/8 round if like to file this into a tapered octagon.

[rich pierce]

The barrel will probably be 4140, which is harder to file than mild steel. Other than that, all you need is a square and a file and a lot of experience filing to dimension and a couple days. I would leave the 3 bottom flats round.

[Goo]

I have heard rumors and that 4140 is not appropriate for black powder barrels.  I have read that this alloy work hardens over time .  I have heard that  mild steel like 1018, 1020, 1024 is best because it has a low carbon content and will not work harden and it is close to iron units character.  On the positive note you could probably use modern gun. powder in that modern steel barrel.   I am quite certain opinions will be all over the place on this so do your research and make your best decision.

[Mike Brooks]

I'd be concerned with the twist.

[rich pierce]

I'd be concerned with the twist.

Agree it would be a plinker at best. Shallow grooves, fast twist. Not great for round ball.

[Bob Roller]

I have heard rumors and that 4140 is not appropriate for black powder barrels.  I have read that this alloy work hardens over time .  I have heard that  mild steel like 1018, 1020, 1024 is best because it has a low carbon content and will not work harden and it is close to iron units character.  On the positive note you could probably use modern gun. powder in that modern steel barrel.   I am quite certain opinions will be all over the place on this so do your research and make your best decision.

When I was i High School I made 2 of these 22's,one with an octagon barrel from a Remington and another round barreled from Bannerman's in NYC. Jim McLemore* made or maybe still does make barrels for muzzle loaders from one of the 4000 series steels,4150 Certified for for the 50 BMG. I bought a bullet mould for a 22 Hornet with a special base for a gas check that when used as cast it started easy and with 10 grains of 4fg
DuPont was NOT a toy.I used a drum and nipple on both rifles and the locks were from P.I,Spence in Marietta
Ohio.
*Jim told me that he would not consider making any gun barrel from materials not certified for them.
I don't know if he is still active or not and he and I are both closer to 90 than 80.I hit 87 on March 27 and right now have almost no interest in working on anything.Good luck with the 22 project and the filing octagon.
Bob Roller

[HSmithTX]

Find a friend with a mill. If not I would file 4 flats as if it was going to be square, get them square to each other and then put the other 4 flats on the rounds that are left.  I might not do the two flats on the sides when down in the stock but I'd do 6 to have something to square off of.  I'd probably spring for an air file to rough them in too,  get the bulk of the metal gone. 

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[JLayne]

Just curious. Wouldn’t the rifling in a modern (off topic) barrel be too shallow for patched round balls? Not being critical. Just curious as all of the traditional Muzzleloaders I have seen have deep rifling in comparison to modern barrels.

Jay

[Carl Young]

I made a pistol from a 8" piece of an octagon Remington barrel many years ago. Used .22 pellets for projectile like a little minnie ball. First shot was no powder just a #11 percussion cap and it shot through a cardboard box and the 3/4" pine board behind it. Usually shot it on a 15 yard target with 5 grains of 4f.

Have fun, but don't underestimate the power of a little caliber or load.
Carl

[Daryl]

Typical 16" ROT and .002" deep rifling.  The Diablo shaped pellet would make a better projectile than a patched RB, for sure. Actually, one of the air rifle slugs would be better yet, however
no grease grooves.
What was read about 4140 work-hardening with low pressure BP loads is Bunk Scrap. That's about as mild as I can say this.
Seems to me it is highly unlikely a .22 LR barrel is made from 4140 to start with, 1116? or is it 1016?

[Camerl2009]

This is a Marlin micro groove barrel but I was planning on .22 pellets.

I figure 5gr or so of finer powder will get a .22 pellet flying pretty fast.

Ik this as been done before I read a thread on here and their a video with one made from a 10/22 barrel.

[Scota4570]

I did two of them years ago.  One was a cheap 1970s Winchester barrel.  The rifling was deep enough to work with pellets.  I did make a size die to reduce the skirts a tiny bit.  I use Benjamin pellets. 

The second one was a Remington M12 barrel.  It never shot well.  The grooves were more subtle.

[Daryl]

Filing a round barrel to octagonal, is quite a job. Been there.

[Hudnut]

Essentially you are making a black powder equivalent of a pellet gun.
A half round, half octagon barrel from something like a Stevens Favorite with a liner installed might make a diminutive little rifle.  I bet a .32RF Favorite barrel with a bad bore would be really cheap, and would be very easy to line with a 5/16" liner.  Hardly any steel to drill out.

[gunmaker]

In one many museums in Vienna, Austria there is a Jager rifle with a short oct. bbl.
!/2 way down it's twisted and left side flat becomes the top...... go man go.

[KC]

When I was i High School I made 2 of these 22's,one with an octagon barrel from a Remington and another round barreled from Bannerman's in NYC. Jim McLemore* made or maybe still does make barrels for muzzle loaders from one of the 4000 series steels,4150 Certified for for the 50 BMG. I bought a bullet mould for a 22 Hornet with a special base for a gas check that when used as cast it started easy and with 10 grains of 4fg
DuPont was NOT a toy.I used a drum and nipple on both rifles and the locks were from P.I,Spence in Marietta
Ohio.
*Jim told me that he would not consider making any gun barrel from materials not certified for them.
I don't know if he is still active or not and he and I are both closer to 90 than 80.I hit 87 on March 27 and right now have almost no interest in working on anything.Good luck with the 22 project and the filing octagon.

Bob, I have to say for being 87 years young, your detailed memory of things never ceases to amaze me. I have trouble remembering yesterday sometimes.

[Camerl2009]

Trying to figure out what to thread it in my head 5/16-24 seems to be about right

[taterbug]

might consider 3/8 or 7/16, just to get the threads further away from the rifling and give a wider shoulder to work with. 

[Bob Roller]

When I was i High School I made 2 of these 22's,one with an octagon barrel from a Remington and another round barreled from Bannerman's in NYC. Jim McLemore* made or maybe still does make barrels for muzzle loaders from one of the 4000 series steels,4150 Certified for for the 50 BMG. I bought a bullet mould for a 22 Hornet with a special base for a gas check that when used as cast it started easy and with 10 grains of 4fg
DuPont was NOT a toy.I used a drum and nipple on both rifles and the locks were from P.I,Spence in Marietta
Ohio.
*Jim told me that he would not consider making any gun barrel from materials not certified for them.
I don't know if he is still active or not and he and I are both closer to 90 than 80.I hit 87 on March 27 and right now have almost no interest in working on anything.Good luck with the 22 project and the filing octagon.

Bob, I have to say for being 87 years young, your detailed memory of things never ceases to amaze me. I have trouble remembering yesterday sometimes.

I can't tell you or anyone else what I had for supper last night.I got a note recently telling me Jim McLemore is ill and I know we are close in age so praying for him and a recovery is a good idea.God gets the credit for my own good health and memories of long ago events and people.About a year ago I got a call from a man who wanted to know if I remembered the overhead cam timing on the last Duesenberg car I worked on and I think this car was posted on this forum in a photo taken about 15 minutes after we restarted it.I still remember that timing after all these years.I filed it in trivia.I remember rebuilding the hydraulic brakes on one of these cars and when the owner came to get it I told him the brakes were not working so we installed a 5 mile Klaxon horn and he'd have to use the hand brake .
Thank you for the note and I AM thankful for my health and memories and NO table top covered with pill bottles and only a once in awhile Tylenol Arthritis pill for my right shoulder.
Bob Roller

[kutter]

First do a little math on the round bbl's end diameters.
Figure what octagon size (across the flats dimension) you can actually get out of the round dia(s) you now have.

It's sometimes surprising how small that ATFlat size ends up with a given round dia to start with.

Then work itself can be all done by hand of course.
Dragging a file down to draw down each flat can be real entertaining.
I personally would use a belt grinder to carefully rough out the 12,3,6&9 flats.
A coarse grit belt like 60 or 80 grit cuts very fast but cool. Easy to control too.
When close,,Then draw file them to straight edges and flat.

Then use their finished position edges as the guides to lower the oblique flats down to them.
Again the belt grinder can be used to rough out that work. Then draw file down to the finish line/edges.

[Jim S]

Making small parts with just hand tools is satisfying and fun, but filing that barrel would be too much for me.  A milling machine is called for I think!

[Bob Roller]

When i was much younger I did file a 22 pistol barrel from round to octagon,The next one was a 25 caliber and I used a milling machine and the the top flat was tapered.I think I sold it to someone on this forum.
I would not even consider that much filing now.If you must,file it square and then knock the corners off. .
Bob Roller

[Daryl]

This was a 7/8" round Bauska blank, about 7/8" in diameter. I decided to file flats on it and taper the rest round. only the top 5 flats are filed. The bottom of the barrel was left mostly round,
so the bore is not in the middle at the breech. It is currently .820" side to side on the breech flats and .795 at the front end of the flats, so it is slightly tapered. The breech end of the round
part is .734" and the muzzle of the 29 1/4" barrel is .660".
So, yes, you can file flats. I used an auto-body file with huge rounded teeth for the job. It takes off curls of steel. The file is now dull, but it was sharp when I started.
So, yes, you can file a barrel from round to octagonal - or with only the top 5 flats cut. I did a little at the breech as well, on the bottom to fit a TC Seneca.
Trying to remember when I did this - likely 1980 or so.

[Camerl2009]

might consider 3/8 or 7/16, just to get the threads further away from the rifling and give a wider shoulder to work with.

I was thinking about that just didn’t know how far to go it is 11/16 round at the breech end and 5/8 at the front. Didn’t want to get too thin in the breec.

[taterbug]

yep,you're right.  i misread the breech diameter.  3/8 is still possible.  There won't be much pressure with the powder charges that will be in there. 

Have you figured out yet how wide the flats will be?  They are not very big...