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Thread: Progress on rifling machine and rifled choke tube!

  1. #41
    Boolit Grand Master

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    I am just getting bits together now to make the barrel adapter, muzzle brake and choke tube. I have some old Chevy axles that are just the right size and tough steel. I have read that they are at least 1040 and possibly 4140. Regardless, they are a lot tougher than the barrel I will be putting this onto. I had to anneal the steel and it is still tough.

    I have been thinking about using a choked gun in the future and cut the rifling from the muzzle. A modified or possibly even improved cylinder choke should have the right bore diameter and enough wall thickness to rifle if the choke is machined. I have a couple of guns with swaged chokes and I doubt there is enough barrel wall at the muzzle to allow for rifling. My Browning fixed choke barrel has a nice long machined choke and thick barrel walls. It is not a candidate for rifling though!

    It might be a bit tricky to rifle and not start cutting the full bore walls though unless the choke is fairly tight to allow deep enough rifling and a bit of a gap to the full bore.

    First, I have to machine all the bits then rifle a choke tube to try this.

    Again, the goal being something I cannot buy which is deep slow twist rifling suited to round balls and full bore "square" slugs.

    I have to turn my cutter head down form 3/4" pipe ID to suit a bore of about 0.700" to maybe 0.710" then reset the cutter. I just need more time! Work gets in the way but I need the paycheck too.

    Longbow

  2. #42
    Boolit Grand Master


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    Greetings Longbow
    I am impressed ! This is as good as finding a cool spring out in a hot desert.
    How I like to see a plan come together and works well while being simple.
    Mike in Peru
    Last edited by missionary5155; 05-02-2014 at 02:22 PM.
    "Come unto Me, all you who labor and are heavy burdened, and I will give you rest." Matthew 11:28
    Male Guanaco out in dry lakebed at 10,800 feet south of Arequipa.

  3. #43
    Boolit Grand Master

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    Mike:

    Well, the rifling machine works but we have as yet to see if I wind up with a Paradox gun equivalent of just a fancy muzzle brake!

    I have started turning pieces but it will be a while before I am done.

    First projectile down the bore will be a 0.735" round ball. If that works then I will try some conical slugs. If not then we will cross that bridge when we get there.

    Longbow

  4. #44
    Boolit Master
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    Just wondering about this and will rifling either a screw in or if you did a whole barrel affect the wad with shot if one was to send a shot load down the tube? I am really enjoying this as I have some shotgun barrels waiting for me to make bp actions for them and it would be neat to shoot a slug or turkey shot load out of same barrel with acceptable accuracy.
    Look twice, shoot once.

  5. #45
    Boolit Master

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    nekshot, a rifled barrel will create a "donut hole" pattern with shot - you'll hot everything but the target.

  6. #46
    Boolit Master

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    Longbow
    Most of the reading that I have done states to rifle the barrel from the breech end rather than the muzzle. Idea being , as things wear you tend to get a taper bored barrel tapering smaller to the muzzle. According to the the great kahuna's this is the hot set up for accuracy. A tapered out barrel tends to spray or scatter things as they come out.
    Just a thought.
    Facta non verba

  7. #47
    Boolit Grand Master

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    Yup, that's what I have read too. My take is that the cut "fibers" or "teeth" lay pointing forward when cutting is from breech to muzzle. My Toad Hall book also says to rifle from breech to muzzle but no particular reason given that I have seen. Whatever the reason, I did my pipe test choke that way and had already cut a "forcing cone" in it first. I plan to have a gap of about 1/2" to 3/4" between muzzle and tube based on what I see in the Pachmayr Power-Pac choke/muzzle brake design so need to allow for some lead in to the rifling.

    I have started work on the barrel adapter but it is on the back burner for a bit while I make arrows for an upcoming archery shoot. I will get back to it shortly though.

    Longbow

  8. #48
    Boolit Master

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    Now there's a man with his priorities straight - and his arrows too, no doubt! For someone of your skills kent they must be footed port orford cedar, tapered with hand chopped, shield cut wild turkey feathers and a bone nock! ya'll punch paper or 3-d?

  9. #49
    Boolit Grand Master

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    Hogtamer:

    You give me too much credit!

    I have footed Port Orford cedar arrows with walnut and single fish tale splice but find it a bit time consuming so I came up with a taper drill tool and now use the same taper as for points when I foot arrows. They look good an dshoot well and are much easier and quicker to make... and I am lazy!

    For the last several years I have been shooting yellow cedar shafts a friend cut but am running out and he has no more so Port Orford it will be next time.

    I self nock and whip... no bone nocks. I do cut my own fletch from full length feathers but not traditional style. I came up with a short high 4 fletch that works very well for me so I have never gone back to 3 fletch. I made my own fletching jigs so I can do 6 arrows at once (one fletch each). Goes pretty quick that way.

    We are going to the B.C. provincial traditional shoot on the 3rd weekend in May. it is a great shoot ~ 3D.

    Longbow

  10. #50
    Boolit Grand Master

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    I am finally back at it and working on my rifled choke tube again! Yeah... I am slow!

    I was looking at the drawings and 3D model and it suddenly occurred to me that the way this thing is designed that the tube may oscillate when the slug hits it. The threads are near the muzzle leaving a fairly large overhang behind but even if I moved the threads and made the threaded section longer the tube could still oscillate.

    I am looking for feedback on what you guys think.

    I am beginning to think there should be a spigot or mating tapers at the downstream end (shotgun muzzle end) to stabilize the tube.

    It does have a large shoulder to butt up on but I really don't want to go through the hassle of making this thing to find that the choke tube wobbles enough to affect accuracy. Remember, we are talking thousandths of an inch here.

    How do regular screw in choke tubes fit? Do they have a spigot fit at the end? Doesn't really matter for shot but for a slug it may well be an issue.

    I have attached a PDF file so you can see the cross section of the assembly. Don't worry about the funky thread fit it is cosmetic. I just didn't start in the same place on the parts.

    Also, the gap between the muzzle (barrel adapter on the left) and choke tube on the right is debatable. I have shown it as the Power Pac choke systems show it but I am thinking a 1" jump may be too much especially for slugs in wads. I like the idea of the muzzle brake but the gap could be 1/4" to 1/2" easily and still vent the gas to the brake. The muzzle brake really doesn't have to be there though, it could be a solid sleeve.

    I would like to hear what you guys think then assess and change if necessary before I machine it all.

    For scale the choke tube is 4" long.

    Longbow
    Attached Files Attached Files

  11. #51
    Boolit Master

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    Longer threaded section for support? I don't like the jump either, doubt it will do the slug performance or your ears any good. Glad to see you back at it!
    "My main ambition in life is to be on the devil's most wanted list."
    Leonard Ravenhill

  12. #52
    Boolit Grand Master

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    Hogtamer:

    I am thinking of not going the muzzle brake route and leaving the sleeve solid along with either a spigot for for the back end of the choke tube near the muzzle or using a tapered seat at the barrel adapter so the choke tube seats on that to center it and support it. I am thinking 45 degree or maybe even 60 degree seat so it is solid but not locking.

    I was looking at a longer thread but don't like the idea of a long thread because I think it will get gunked up with powder residues and such and be difficult to remove the choke tube ~ too much engagement and friction if dirty.

    Yeah... noise... I don't have much hearing left now so I don't need to lose any more. I have read that the Cutts Compensators were rather noisy and I have to think the Power Pacs were as well since so similar.

    I'll ponder this a bit more then make a decision and get it built. I am thinking a spigot fit of choke tube to sleeve just past the muzzle is likely the best. That would mean no muzzle brake though which might be a good thing.

    Longbow

  13. #53
    Boolit Master
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    Forsyth Rifling

    Perhaps the twist rate of Forsyth Rifling would be of interest.

    http://choose-miey.blogspot.com/2011...my-annual.html

  14. #54
    Boolit Grand Master

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    A good read and matches what I have read about the rifling twist in large bore guns. 12 bore needs about 1:120" twist. I decided to go to 1:72" for lower velocity and use of longer slugs in hollow base. 1:72" maybe a bit quick but way better than 1:36" which seems pretty common now for both fully rifled barrel and rifled choke tubes.

    I have read about the Fosbery ratchet rifling for Paradox guns and confilicting reports of twist rate ranging from about 1:38" to slow ball twists of 1:120". Looking at the muzzles of the Paradox gun in the Holland & Holland publication here:

    https://issuu.com/hollandandholland/...ld_15_complete

    the rifling twist looks very slow to me. I wonder if H&H would respond to a question? I'll try to find a contact.

    Regardless, I decided a relatively slow twist would be better than the current trend of fast twist for sabot slugs. Not sure if 1:72" is too fast or not but will find out because that is what I built my rifling machhine to cut. I can remake the worm and nut but will try the 1:72" unless someone tells me it won't work.

    I also like the narrow lands in the Forsyth rifling system. My plan is narrower lands than groove but I wasn't going as narrow as the Forsyth rifling appears to have. I may change that thought.

    Slow going but making progress. I did a bit of machining yesterday. One day it will be finished.

    Longbow

  15. #55
    Boolit Master
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    Last edited by RMc; 10-20-2016 at 11:26 AM.

  16. #56
    Boolit Master
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    I've only just seen this fascinating thread. First, very shallow rifling indeed is fine for a muzzle-loader with lead-to-bore contact. Metford found that scratches made with coarse emery on a lead lap would work until they eroded smooth, and it doesn't have to be very deep to resist black powder erosion. What is different in your situation is the bullet meeting the choke when it is practically at full speed, and having to take the rifling then. That is why Fosbery found deep rifling to be necessary. There is nothing very original about either the twist of the Forsyth rifling, and the narrowness of the lands is just an extreme example of what was common practice. If you try for narrow lands it would be a good idea to have an odd number, since one directly opposite the cutter would reduce the tendency to chatter. Extremely narrow lands are also very easy to wear with a cleaning rod or ramrod, so a protecting bush on the rod would be useful.

    There are rifled choke tubes available, but some are made to spread small shot for hunting in close cover, and it is possible that some of those might be more deeply rifled than you would want with a solid ball or slug. Normally the choke tube can't act as the kind of bore obstruction which causes a bulge. But a long extended one might. Here is an example of a double ring-bulge I provoked experimentally in a derelict single shotgun. The first bulge is produced by the pressure of gas, which is very elastic, piling up behind the obstruction. So unless the obstruction is totally immovable, the bulge will occur something in the region of an inch further along the bore. The second bulge is produced by that gas cushion bouncing back, bouncing again from the breech face, and coming back to hit the obstruction for a second time. It happened in less distance than the length of an extended choke tube.

    Incidentally the use of shot in a rifled bore or tube shouldn't make much of a doughnut pattern if everything else is well. The shot is widened by centrifugal force, but the shot near the centre are describing a spiral of much smaller diameter, so their outward movement will be less. What may happen is that if the outlying layer of shot are deformed by the rifling, they may fly wide of the rest of the pattern. But that has been made less of a problem than it used to be, by the use of shot-cup wads.

    Twisting a square metal rod to make your rifling guide rod could work well, but it needs to be good quality metal and closely dimensioned if the spiral is to be totally consistent. You can't do it hot with any sort of equipment the amateur is likely to have, for the same reason. A gain twist is mildly beneficial if done well, but people warn against rifling which accelerates and then decelerates, or vice versa. I don't know why they should be very different, but they may be.

    Click image for larger version. 

Name:	Double ring-bulge from obstruction.jpg 
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    One possibility would be to cast an alloy plug around the rifling rod in an existing rifled barrel. For a good bullet muzzle-loader a 12ga Hastings barrel would be ideal, and you could even do it without damaging the barrel of an existing gun. You could use this setup either directly or to cut a groove in a guide cylinder. Do it with a ball burr or ball nose end mill in a metal cylinder, and you could solder a matching round wire into it.

    Forty passes per groove sounds about right, and they don't make paper shims that thin, although they are find for spill boring a smooth bore. I think you need the usual arrangement of a square or rectangular bit sliding in an inclined trough, held by a spring at one end and an adjusting screw at the other. I'd prefer a brass or bronze cutter holder, which if necessary you could make up by silver soldering pieces of metal together and turning the resulting block round. Any very hard wood should do, or a laminated phenolic plastic such as micarta or tufnol. In this case I would line the bottom of the slot with metal.
    Attached Thumbnails Attached Thumbnails Single ring-bulge and split, produced by bore obstruction.jpg  
    Last edited by Ballistics in Scotland; 10-20-2016 at 12:04 PM.

  17. #57
    Boolit Grand Master

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    BIS:

    Good to hear from you.

    I have already built my somewhat crude but effective rifling machine. I cold twisted a piece of 1/2" square bar to as close to 1:72" as I could determine. It is polished smooth then I cast wheelweight lead around it so perfect fit. I had a heck of a time getting it to move at first so whacked it with a mallet then sprayed with WD40, repeat until it moved, more WD40 and eventually I have a nice slide fit with no slop.

    I made a wooden rifling head using a piece of file for a cutter and proceeded to rifled a piece of 3/4" pipe which came out very well. It was work but it worked.

    I do not plan on using extremely narrow lands, probably about 1/2 the wide of grooves of maybe a little wider.

    I like deep because as you say that slug is ripping along when it meets the rifling. Fosbery used ratchet rifling I think to maximize "traction" on the driving face and minimize slug distortion. I woulc like to know the typical twist rates though. My understanding was that bore guns used slow round twists for round ball and "square" slugs but IIRC the Ross Seyfreid article mentioned 1:36" twist for his Paradox gun. In any case, I have been told both slow and fast. I have to think that if there is no skidding then slow is best for round ball or square slug.

    I have seen the use of an existing barrel to make a rifling guide then use that for rifling a new barrel to same twist but I do not have anything rifled to 1:72" or slower. The closest I have is my old CVA Hawken kit rifle with no-removable breech plug so a no go and it is 1:66" so even a bit faster.

    For a short rifled choke tube the twisted bar works just fine and is easy. I was planning to build a rifling bench on the Seabolt pattern and bought the Toad Hall book:

    http://toadhallrifleshop.com/rifling-worms-video/

    but that is a project on its own and requires significant room just to store the rifling bench. I already have a bowyer's bench I built and it sits on pour back porch now. I really don't need any more "furniture" that only hold one person and not so comfortably! If I was making a full length barrel i would either use an existing barrel or make a rifling bench but my small machine works for this.

    Actually the shimming worked very well, I used parchment paper that is about 0.0015" thick but due to compression it worked quite well. I ran through each groove until there was little resistance then indexed and repeated for each groove. I plan to do the same for the choke tube with the addition of indexing through each groove with the finishing shim pack to make all grooves the same.

    I agree that a sliding cutter on an inclined face would be much better and if I were to go into production I would get much more sophisticated with my rifling machine and head than I have for this little project. I figure if Bookie can make a wooden worm and rifle a full length barrel accurately my twisted bar should do as well. The ODG's did it too and made some fine weapons.

    I am just rethinking the choke tube and muzzlebrake after looking at the overhang and may change things some. I will likely rough turn a piece of round bar for a choke tube though then bore and rifled it without working the outside just yet. If the rifling turns out well then I can change thread length or location later then finish the choke tube later and make muzzle brake/sleeve to suit. I want a rifled tube before I do all the rest of the work.

    Longbow

  18. #58
    Boolit Grand Master

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    BIS:

    It occurs to me that you live in the land of Paradox guns and bore guns. Do you have access to any? I am really curious about twist rates especially for the Paradox guns.

    If you could get that info I would be forever in your debt.

    Longbow

  19. #59
    Boolit Master Cap'n Morgan's Avatar
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    Longbow,
    I would skip the muzzlebrake holes (little, or no effect in a shotgun) and extend the choke-extension for a tight fit over the barrel for at least 1.5" This would give you a good barrel/choke alignment even if the choke should work loose. Make sure you have at least .01 freebore/taper in the choke - perhaps even a smooth section to guide the slug before it meets the rifling.
    Cap'n Morgan

  20. #60
    Boolit Grand Master

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    Cap'n Morgan:

    Good to hear from you! It has been a while.

    I have changed the choke tube and muzzle brake a bit to move threads to the mid point, shorten the muzzle brake and reduce clearance gap to .375". Otherwise same choke tube of 4".

    Yes, others have commented on the noise from the muzzle brake being objectionable.

    I will likely leave some holes in the muzzle brake/sleeve simply to keep crud from building up. I had a Pacmayr Power Pac many, many years ago but no muzzle brake so I made one and installed it. It looked much like my new MK I muzzle brake. Actually it was not that noisy but maybe because hole area was smaller than stock? Anyway it looked good and when shooting BP loads was pretty spectacular with the muzzle flash. I was playing with BP and 0.690" ball loads back then.

    I may start with no holes to see how it goes then possibly add some to see how that works or what effect it has. I can always make another sleeve.

    The choke tube design is 4" long and has a gentle tapered lead in from beyond groove diameter to bore diameter over 0.75" so the slug will get a nice tapered lead in. I may add a short groove diameter smooth section too or maybe a steeper taper then a short groove diameter smooth section more like a chamber throat. I am undecided as yet and looking for opinions so thanks for that.

    I hadn't thought of a spigot fit to barrel. Not a bad idea. I'll ponder that some and maybe model something up. It would likely be easier to thread the outside of the barrel and screw the tube onto that eliminating barrel adapter and sleeve. I would still be able to make the choke tube heavy duty unlike the thin internal choke tubes. I have no way of threading the barrel though so would have to get someone with a larger lathe to do that.

    Alignment is one of my concerns with so many pieces. On that line I could eliminate the sleeve and screw the choke tube directly onto the barrel adapter making it all external. With some barrel extending past the barrel adapter I would get the spigot fit and less pieces.

    Hmmmmm... that is certainly worth taking a look at.

    Lots of things to think about.

    Thanks for the input.

    How is your Brenneke project going? It seemed like you were making good progress last post but I haven't seen anything for a while. My preference is still an accurate smoothbore slug and you were well on your way there.

    Longbow

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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check