12 guage barrel project

[missionary5155]

Anyone know someone who can rifle the last 4-5 inches in a 12 guage shotgun barrel with 1-90 to 1-100 twist ?

[Cactus Farmer]

Might be hard to rifle just the last few inches due to cut rifleing cutter design and the slop in the gear train. I'd guess you could put a stop on the machine and only go so far but pushing the hook cutter backwards wouldn't do the cutting edge any good. Is this to spread shot or for solid projectiles?How many grooves do you want? Much easier to rifle the whole tube.:castmine:

[missionary5155]

Good morning Cactus Farmer...
Well this is my continueing pursuit of shooting Round Ball in 12 gauge. You sound like you have experience in this rifling buisness. I am not trying to re invent a wheel... The idea popped up writting with some other fellers who are serious launchers of 12 gauge projectiles. My goal is to get a RB in a regular plastic shotcup accurately out to 100 yards. I am looking at a 1-100 ( 1-90 up to 1-120 would be acceptable) twist . I would supply the barrel. It would be a Mossberg for a model 500. The rifling will not need to be deep.. such as for a patched ball as I will be using a tight fitting ball in a shotcup... probably stay with Winchester.
So that is the plan.... I was thinking of the Full choke barrel and rifling the muzzle area simply because the British used the system... I would not be oppossed to a full length rifled barrel. What are your ideas ?
Mike.. alias Missionary 5155

[Junior1942]

Doesn't someone made a rifled screw-in choke?

[missionary5155]

Good morning Junior1942. Yes there are but they are rifled FAST (1-38 or so).. more for the slug type projectiles. I am looking for rifling made for round ball. If a RB out of 12 Guage can fly as accurately or better than the slugs with tails,feathers, fins.... why bother. And I think with the proper rifling there is no reason they should not. I have a FAST twist slug barrel... does OK.. but just maybe a 1-100 twist will be that much better and really let the RB SHINE ! Plus there should not be any problem if I decide to go with LONGBOWS "Full bore" ideas. Fast twist does not like PURE lead...

[Junior1942]

Well, the easiest thing to do would be to take an Extra Full extended choke and rifle it, not the barrel. Should be much cheaper.

[missionary5155]

Thanks Junior1942.... That is another option. Sure would be easier shipping a choke about... And as CactusFarmer stated that would be easier to rifle on complete passes. What a GREAT place to get in on the thinking of others.

[GARD72977]

I would consider a broach made from high speed steel. If you go to one of the fourms for home machinist you may be able to find some one that will grind it for you. Some one with a mill and a universal indexer attached to the table woud give you the twist. A grinding wheel in the mill would be a easy task for someone with the equipment. The broach would be great for the choke. It would also be possible to broach the last few inches of the barrel then press the braoch out the front. Just an idea. Some one here may have the equipment to do this. Im no pro just an idea

sorry i had to edit some of my spelling. It may make more sense now

[GARD72977]

Alright - this is the kind of project that gets my attention


Option 1
use a .69 ca black powder barrel (if it is the same as a 12ga dia.) find a surplus barrel and use a small section to make a choke insert. I would have the right twis t for round ball. this is my least favorite idea!

option 2
Make a broach from HSS. I dont have the attachment to give the helix nessary for a flat bottom rifle cut. There is a way around this. If the broach is ground at a angle it will give a Rifiling that is angled in the groves. I dont think this would hurt anything. In fact after reading about barrels that have flat bottom groves it leads me to belive that some do not. Why would they mention it? I dont have the measurements for a 12ga bbl. There are some areas that amatures like us could cause a problem. How high do we want the lands. How much pressure will it build? Will there be a leading problem ( the round ball does not seal in the smoothe barrel. What happens when the lands dig into the soft lead?)

I think the lands should taper from nothing to .0625 for a starting point. I have concerns about the first shot and pressure. I am also concerned about leading and building pressure. The good point is that the problem would be at the end of the barrel and not at the chamber right by your face. I still dont want something blowing up at the end of the barrel

The taper in the lands would be accomplished by using a taperd hole much like a choke and running the broach from the bottom ( large dia side) The broach would need to have a good bearing ( Of some sorts maybe just a l large dia single ball bearing in a small indention to keep it on center) to let the broach turn with out obstruction when pressed through the choke.

We would have to figure out the math for the twist. If the HSS rod was taperd with a .0625 larger end and was set on a surface grinder at the correct angle (for rate of twist) It would give a cutter that would rotate when pressed through the choke. Since the cut is so small I dont think much pressure would be nessary. Im not convinced that 1/100 is the right twist. We need some research on .69 cal rifled blackpowder guns that shot round balls

some one check this math. For argument sake lats say that the dia is .69 and we want a 1/100 twist. The broach is 4"
The circufmrence of .69 is 2.17 - 2.17 divided by 25 would be .0868 this would be 1.24 deg ( that is a precision setup !!!)

Any one think it would work?
Dont deduct for spelling.

[longbow]

We kinda have two threads going here between Special Projects and Casting For Shotguns but I am with Missionary in his quest.

I have often thought the Paradox gun idea was rather cool. Basically a shotgun but with rifling for the last few inches of barrel. However, like missionary, I like the idea of a full bore RB or square slug both of which like a slow twist of 1:100" or thereabouts for 12 ga.

Modern choke tube twists of 1:38" or so are to suit sabot slugs plus the fast twist results in rather severe torque that can really wind the choke tubes down hard. The slower twist shouldn't do that plus it is much less likely to strip a round ball. Possibly the square slugs would have enough bearing surface to pick up the fast twist without stripping.

My goal is 0.735" RB with a slow twist choke tube. I have tried them through a fully rifled barrel at 1:38" twist and got 2" groups at 50 yards with open sights and being slapped silly with recoil. So much better than I expected.

However, 1:38" in a few inches of choke tube is a little fast to pick up by a ball travelling at around 1400 to 1500 FPS when it meets the rifling. Also, best accuracy for RB's is generally reported with slow twist barrels. I have not shot the 0.735" RB's at 100 yards yet so cannot comment but even if accuracy from a fully rifled barrel is good I'm betting the short 1:38 choke tube would not do well.

I am checking with a couple of 20 & 12 ga. RB muzzleloading rifle makers as to whether they will rifle short sections of barrel at their 1:104" twist or maybe a full length barrel blank that could be cut (in my case) into choke tube lengths and machined.

I will likely never be able to afford, or at least justify, the expense of a double rifle but a side by set up to shoot slugs is not a bad compromise in my view. Either slow twist rifled tubes or possibly missionary's idea of rifling the choke or full choked side by appeals to me.

If all else fails I will make myself a short rifling rack for 1:60" or slower and rifle my own choke tubes to try.

Anyway, I'm rambling a bit (sorry about that). There is some good discussion going on in the shotgun section too but I thought if you missed it I'd add this.

Longbow

[GARD72977]

I know that I am blowing this up but I had another thought. The braoch would be made in steps rather than taperd. In a four inch broach with .0625 cutting depth somewhere around 4 steps would give a cutting depth of .0156 per tooth. A taperd broach my be beyond the capacity of a home shop.

[missionary5155]

This is getting REAL GOOD ! I have threads at other sights and nothing that I can really add. One suggestion (Junior1945) was to get a "Full Choke Insert..screw in" and get that rifled... may be easier for the rifling smith to make full passes. Another suggestion was a 12 gauge rifled LINER soldered into the appropriate barrel... that may be a simple solution if the appropriate SLOW twist is available.

[GARD72977]

With proper bearing the broach would twist 1 time in 100 inches if the angle of the ground cutting surface was 1.24 deg from front to rear of the broach. THIS IS THEORY! ( also some one more knoledgeable should check the math) I will provide a cad drawing of cutter to make it easier to understand why the broach will twist.

[Junior1942]

I'd contact one of the after-market choke makers. Surely they've researched this while searching for a possible new market.

[missionary5155]

Thanks again JUNIOR1945... that is another possibility.

[longbow]

So far as I have found all the new rifled choke tubes are fast twist "sabot discarding" choke tubes. Not to say someone doesn't or couldn't make a slower twist, I just haven't found one.

Dixie makes some real nice full bore slugs that perform well from fully rifled barrels but James comments that rifled choke tubes don't do so well. It is a lot to ask a heavy slug travelling at 1400 to 1500 FPS to pick up a fast twist like 1:38" from a short choke tube.

Call me crazy but I like the idea of a modern Paradox gun for RB or "square" slugs.

Longbow