4 bore barrel balance

[pennsyltucky]

im workin on a large build. a 4 bore. i have the barrel blank put together, and i have been really torn about what contour to cut the outside. i cant do swamped, and it cant stay straight octagon. so which will balance better, oct-round or tapered octagon. both will weigh very close to the same when finished. is there something magical about one or the other? or maybe tapered octagon to round? also, any tips on what i should scale up on the stock to make it look a little less out of proportion? the barrel is only 1 3/8 across the flats, so its not huge, but certainly bigger than the 15/16 or 1" barrels. im planning on maybe inletting it slightly deeper, and using a removable ramrod tip so i dont have to allow for the huge 1" tip. any other comments or suggestions would be nice.

 

[ssettle]

im workin on a large build. a 4 bore. i have the barrel blank put together, and i have been really torn about what contour to cut the outside. i cant do swamped, and it cant stay straight octagon. so which will balance better, oct-round or tapered octagon. both will weigh very close to the same when finished. is there something magical about one or the other? or maybe tapered octagon to round? also, any tips on what i should scale up on the stock to make it look a little less out of proportion? the barrel is only 1 3/8 across the flats, so its not huge, but certainly bigger than the 15/16 or 1" barrels. im planning on maybe inletting it slightly deeper, and using a removable ramrod tip so i dont have to allow for the huge 1" tip. any other comments or suggestions would be nice.

A 4 bore.. man I have to see that. I'd go with octagon to round with a taper. keep as much meat where it counts. I'd also go with a wide butt to take up the recoil that beast is going to dish out. I have a black double barrel 10 gage and it kicks like you wouldn't believe. A 4 bore hurts just thinking about it. remember picture, we gotta have pictures..Ssettle

 

[BrownBear]

I haven't handled or shot a 4-bore, but years ago I was blessed with an older friend who collected, and more importantly SHOT, lots of double rifles. If I'd help with the chores at the reloading bench I could pretty much shoot what I wanted.

Along with the large assortment of cartridge guns he had two 8-bore MLs. Coincidentally one of them balanced light in the muzzle and the other balanced heavy, even if there was ony an ounce or two difference in their weights. While the light one was really fast handling, it just about killed you compared to the one that was muzzleheavy. The difference in recoil was really noticeable.

I'm guessing the same will be true with your 4-bore. It's a guess, but one based on experience. If it was mine, I'd decide whether I'd rather shoot it fast or shoot it lots. But you won't be doing both.

 

[Roy]

I made a few wall guns with a 1" bore and one blunderbuss.... they had about a 2" breech. Hopefully I have misunderstood and you have more than a 3/16" wall thickness.

 

[Mike Brooks]

Your making a bomb. An 1 3/8" breech is too small for a 4 bore. It leaves you with 3/16" barrel walls, and you still have to cut threads in it for the breech plug! :shocked2:
The last 4 bore I built had a 2" breech.

 

[Mike Brooks]

Looks like Roy and I posted at the same time with the same warning.....

 

[Roy]

Looks like Roy and I posted at the same time with the same warning.....

Scarey huh? I didn't mean posting at the same time... :shocked2:

 

[paulvallandigham]

I can't imagine any use for such a large cannon, and I certainly would make it on a larger diameter barrel! 2 1/2" would be more to my liking. I have shot an 8 gauge ML shotgun, using 6 drams of powder and 3 oz of shot. It definitely said " HELLO !" The owner has backed his load down to 4 drams( 110 grains) and 2 oz. of shot, but I have argued with him repeatedly that his gun would be a true asset if he reduced that to a 3 dram charge, and 1.5 oz. of shot, like a heavy 12 gauge magnum load. In an 8 gauge, that load would be a pussycat,both in recoil, and in its ability to break clay targets or kill birds.

And that brings me to my final point. With large bore MLers, there is nothing that says you have to stuff so much powder down the barrel that you risk removing your shoulder and head! you can use " reduced " loads and actually hit something! I have shot some light " 20 gauge " loads in my 12 gauge gun and was surprised at how well they patterned. The recoil was barely a shove. For a cylinder bore shotgun, these lighter loads make a lot of sense. The birds have to be inside 30 yards to have a pattern tight enough to hit them, anyway. Why use a load that will filet and pluck the feathers out( while dislocating your shoulder) before the bird hits the ground? :hmm: :thumbsup:

 

[pennsyltucky]

its not a bomb. its high tensile steel seamless .250 wall tubing. flats cut .060 off the OD, leaving .190 thickness. sch80 seamless with 1" ID is .179 wall, and that handles 350gr 1F and 5oz lead with ease. im not worried about the low pressures with blackpowder. a 40" tube with .500 walls would weigh more than 1 man could carry very far. im not building a cannon, just a gun to play with. it will weigh roughly 15 lbs when its done. besides, ill be proofing it to be sure :wink:

 

[pennsyltucky]

I haven't handled or shot a 4-bore, but years ago I was blessed with an older friend who collected, and more importantly SHOT, lots of double rifles. If I'd help with the chores at the reloading bench I could pretty much shoot what I wanted.

Along with the large assortment of cartridge guns he had two 8-bore MLs. Coincidentally one of them balanced light in the muzzle and the other balanced heavy, even if there was ony an ounce or two difference in their weights. While the light one was really fast handling, it just about killed you compared to the one that was muzzleheavy. The difference in recoil was really noticeable.

I'm guessing the same will be true with your 4-bore. It's a guess, but one based on experience. If it was mine, I'd decide whether I'd rather shoot it fast or shoot it lots. But you won't be doing both.

thanks for the post. this bear out in modern shotguns to some extent also. taking 6" off the front of a normally barrel heavy, mild recoiling single shot severely increases the recoil. im sure in part due to the lighter weight, but i think you may be right, and the lighter nose jumps alot farther, making it beat you up alot more... i dont think 44" of 1" bore can ever be called "muzzle-light", but i wonder if there is much difference in how the weight is spread out. like, would an oct/rnd with a center mass at 18" from the breech handle much differently (both carrying and in recoil) than the same barrel thats simply tapered from breech to muzzle, also centered around 18-20"???

i will be muzzlebraking this barrel to fight the overall recoil and keep the muzzle down. its all on paper at the moment, but it seems to me that it will work well :redface: i hope im right.

this is basically the same type tubing that the fella at early rustic arms uses to make his .75 round barrels. his are much thinner walled, and .75 isnt a alot smaller than 1". ive built 12" mortar cannons with the stuff, and you can fill em 1/2 with powder, and half with buckshot if you want. no worries on the pressure :surrender:

 

[BrownBear]

The two 8-bores weighed almost exactly the same, but one (40 years ago, but I want to say it was a Holland) had it's COG right between your hands. Other than the weight, it handled about like a good bird gun. The second (and after 40 years I want to say it was a Greener) had it's balance point shifted forward about 6" as I recall.

All I can say is that with a full charge behind a conical, if you didn't hold the gun right you could bloody your nose with your thumb every time you pulled the trigger when the muzzle took off skyward on the Holland. Same load in the Greener, and you wouldn't bloody your nose, but you darn sure better have your feet set if you didn't want to take a couple of steps backwards.

 

[Zonie]

Folks using any pipe or tubing with the word schedule in its name are, in my opinion, asking for trouble.

They should read both of my comments on DOM and Pipe in this link. It gives some numbers that should be of interest.
PIPE/TUBE BARRELS

Those who have already built a barrel out of this material and have fired it should give some serious thought to continued use of their "barrel".

 

[Mike Brooks]

Do you have an life insurance policy? I wonder if they consider a death by a piece of pipe bomb to be an accidental death or a suicide? :hmm:

 

[pennsyltucky]

this particular piece of "tube" doesnt have schedule in its name. i was just using schedule 80 seamless as a reference since it has worked well in the past. i know that my piece of "tube" will hold much more than my body will stand, and thats not really my issue. i understand the reasons for harping on the safety issue of "tubing" or pipe as barrels, since the next guy reading this may get the wrong idea and kill himself. this tube is many many many times stronger than any barrels made when flintlocks were "modern". like i said, its much stronger and thicker than the early rustic arms tubes, and how many of those have popped? using Boardman's formula, the burst psi for this size tubing with only a 75,000psi tensile is 28,846psi. with a safety factor or 3:1, my working pressure is 9600psi. i could safely fire most modern ammunition in that barrel if it would fit... what pressures do we get with blackpowder? and how much 2F would it take with only 4oz of lead snuggly fit atop to pop a 28,000+ psi tube? im not trying to have a debate on the dangers of different sizes of pipe or tubing, just was wondering about the handling characteristics of different barrel profiles :surrender:

i picked up the recent issue of backwoodsman magazine yesterday... theres an article about just this topic you guys may be interested in and he DOES suggest using schedule 80 seamless "pipe" as a barrel for a slob-job project. he also has a pretty slick lock on it. and the more i think about my use for this arm cannon, the more i think that would be a better way to go than trying to build a nice flinter that is far out of proportion and balance thats a pain to carry and shoot.

now what to do with the 10" i cut off :hmm: a 4ga pistoli... ouch :grin:

 

[Roy]

well I still think its a bad idea... but I do have a question. How are you going to breech it? What sort of plug with that thin wall?

 

[Erzulis boat]

I have made some barrels from scratch for replica builds.

The above barrel from an old build copies a Coaching carbine from a book. The dimensions are identical to the original. Bore is .620 with a wall of .310 across the flats.

Why go against centuries of proven dimensions? A 4 bore with a breech of 2 inches is accepted and will be absolutely safe, no questions asked.

 

[pennsyltucky]

what would you suggest for the breechplug? what would be the proper way of breeching this barrel? i had thought about turning the shank of a 1 1/4" bolt down so i had 3/4" of threads, and 1/2" of bore diameter shank, then sweating the shank tight with something like "silver solder".

also, for you fella's thinking im gonna blow it up, what do you suggest for a proofing load? double a normal load? whats a normal load in a 4.66 bore gun?

 

[Erzulis boat]

I make breechplugs from scratch where required. The carbine build used a .750 diameter plug.

The ideal setup is so that the thread root diameter (valley of the thread) exceeds bore diameter, even by a little bit. That way a shoulder is machined inside the barrel for the face of the plug, and the bore is free from any threads exposed by the plug.

If you do decide to use this tubing for a barrel, I would suggest a custom breechplug made from a solid piece of steel (easier than it sounds) custom fit for the internally threaded breech. You are going to want zero slop, the breechplug should be threaded in without any up/down/side/to side play. You are going to be "Bladerunning" here on wall thickness.

The thread pitch will be of the utmost importance, you have to think in terms of a spiral and remember that the internally threaded breech is basically only as thick as the OD of the cut threads.

I doubt that a commercially available fastener of that diameter will fit the bill.

A 1.125 by 12 TPI requires a 1.035 minimum, so with a 1" bore this would just make it. But what is your wall thickness now? An eighth of an inch at best, because the tap will cut oversize depending on the callout (classes 1B, 2B etc.)

I would be thinking that .375 would be an absolute minimum for breech wall thickness, so that the threaded breechplug has a chance to do it's job properly.

Your wall thickness at the breech face remains .1875, but your breechplug is basically threaded into some .125 wall pipe. If you went with 1.250 breechplug it would be even worse. If you look at the big picture, and lay everthing out, the wall thickness just does not check out. Sorry.

You will probably not blow yourself to pieces, but why push the issue? I have built many custom barrels and would not even consider this as correct dimensionally. My barrels are proven to be safe because I play within the established guidelines.

 

[Russ T Frizzen]

I have made some barrels from scratch for replica builds.

The above barrel from an old build copies a Coaching carbine from a book. The dimensions are identical to the original. Bore is .620 with a wall of .310 across the flats.

Why go against centuries of proven dimensions? A 4 bore with a breech of 2 inches is accepted and will be absolutely safe, no questions asked.

About that lock--could you provide some details and maybe some more photos? Especially of the innards.

 

[Zonie]

pennsyltucky:
Although Boardman's formula will give a slightly more conservative safe pressure value than Barlow's formula, I feel the safety factor of 3 is just great for hydraulic tubing that is subjected to relatively gentle changes in pressure such as opening a valve.
The safety factor for violent changes in pressure is closer to 10, and using this value, your barrels safe operating pressure is much closer to 28846 psi/10 = 2884.6 psi of internal pressure.
Black powder can (and does) produce pressures up past 20,000 psi with certain loads and 2800 psi is actually rather low even for a mild shotgun load.

As for the person who wrote in Backwoodsman Magazine about using Schedule 80 pipe for a gun barrel, he is, in my opinion, an *****.
Please note that I'm not including you in this category.