12 gauge 1 in 8i4 twist octagon barrel

[Greg5278]

I just fired my new 12 gauge octagon barrel on my Ithaca action. The first group was a dismal 2 inches @ 50yds from an improvised rest. It has a freebored chamber, and no forcing cone. It was designed only to shoot big cast slugs. The slugs tested were 775 Grain Truncated cone bullets, and 811Grain Whitworth style. The Truncated cone bullete were not used for the group because I had to zero the scope. It was 2 feet low, and I used all the ammo getting it close.
The bullet holes were all round, and perfectly square. The 1 in 84 twist is sufficient to stabilize the slugs. The old bore guns had twist rates of 1 in 60 to 1 in 140. I will let you know how it works out. Greg

[NVcurmudgeon]

Does it kick like a blue-nosed mule?

[45 2.1]

Greg-
Ross Seyfried wrote a good article about English 12 bore rifles in either Handloader or Rifle some time ago. Wolfe Publishing has a site with the listing of monthly articles to look thru.

[Johnch]

Are you using plastic or brass cases ?
What speed are your rounds going ?

If I may ask what are you going to hunt with your toy ?
Is there a T Rex season that I don't know about ??
Are you using 12 bore rifle data ? or where did you find data ?

And I thought my 50-140 I used to have was big !

Johnch

[Greg5278]

I am hunting Deer, And wild pigs with it. It does recoil hard, but the gun is heavier than normal. I calculate 58 foot pounds of recoil. The muzzle energy is 3300Ft-Lbs at 1400 FPS. Accuracy is good. My loads are in plastic cases. I developed all of my loads from scratch, and hac them pressure tested. I am staying within the 11,500PSI limit for a 5 shot string, and 13,500PSI for any one shot according to SAMI specifications. Greg

[Buckshot]

.............I'm glad to see you post about your shotgun work again. I know exactly zip point nada about the relationship bewteen paper and plastic hulls and brass ones, but have you checked out Graf & Son? They carry the Mag-Tech Brazilian made brass shotshells, and they're all setup to take Boxer primers now.

It would be neat to see a barrel set up just as if for a .729" rifle slug and utilizing those brass cases! I could just see a shell belt full of those honkers around your waist . You'd have to have a backpack with a helium balloon in it to keep you upright and a good set of suspenders!


This is the 32 ga shells from Mag-Tech I use to make cases for a little 1874 Brazilain Comblain in 11.4x42R. These were Berdan primed and I converted them to use the 209 primer. Graf has these on closeout at $6.99/25. I use their 24 ga shells to make .577" Snider cases.


I got to looking at that 32ga hull and thinking, hmmmmm. Wouldn't THAT make a jim dandy big BP cartidge to hurt myself........er, I mean to shoot something with? I can see a tipping breech rifle like a stretched Snider? I suppose the 32ga would be about like a 50-100 or somesuch.

..............Buckshot

[Greg5278]

I am using the plastic cases for a few reasons. The case is not the limiting factor in the gun, the pressure is still limited to 13,500PSI for any one shot. The second reason is that the brass cases have a thinner wall, and do not support a .729" slug very well. They require oversize bullets,wads and gas seals. The cases are not a tight fit in the chamber either. My chamber is cut to minimum tolerances, and supports the hull completely ahead of the case head. I am trying to get the bullet started in the rifling as concentric as possible.

Does anybody know of a long front ramp for an Octagonal barrel that I could use? Williams, and NECG make sights, but they all need significant modification. If I can't find one, I will just have to make it. Greg S

[Buckshot]

Ya mean like this? This one came from GPC and was a couple bucks. It was for a round barrel, but how much work is it to file the base flat? Not much.


The one above I made out of a piece of keystock and filed in the dovetail. With keystok being available in square and rectandle cross section, you'd be able to get pretty close to what you want I'd think.

I made the one on my 7.62x39 Mauser, but don't have a good photo of it. It was made with keystock also. It's rear face is sloped down and I used a thread chasing file to cut crosswise grooves in it. Didn't have a real checkering file. I have to say, it came out looking 'factory'

...............Buckshot

[Greg5278]

Thanks Buckshot for the help, I am going to make a front ramp on the CNC mill. We already have a profile tool to cut 7 or 8 flutes along the ramp instgead of checkering. I have seen some neat texturing done on guns with CNC mills, and carbide cutters. The fishscale pattern is one example. I am tempted to farm out the job to a CNC shop with automatic capability, so make a run of 6 or so. I don't see any reason the mill could not do nice checkering on metal, given the right cutting tool. Greg

[omgb]

Several thoughts here. I have a whole bag full of Korean War issue Winchester brass 12 ga hulls. These take a small rifle primer. I've been wanting to try making a single shot 12 bore rifle for years but just never get around to it. I plan on using BP only. Any way. I was in Don's Sporting Goods in lewistown MT two weeks ago and saw a Handi Rifle NEF/Topper sort of gun (dang if I can't recall the brand) and it had a 12 ga. very think, heavy rifled barrel. Hmmm, if only I'd been a resident I'd have picked it up pronto. Asking price was around $200.

Any way, I have thought about buying an NEF slug gun and having a new barrel made up for it that would be chambered for the brass hulls. This would also require a custom mould. I wonder if Dan over at Mtn. Moulds could cut one? I figure that a single wide grease groove and a LFN with a large meplat would be a real deer slayer at 100 yards or less. Powder charge would be right at 120-140 grains of 2F or 1F and the slug would weigh in at about 800 grains. If the barrel were heavy enough and the over all weight of the gun was around 11 pounds, a good fitting stock and a rubber pad would make it shootable.

R J Talley

[Greg5278]

Dan, will not make 12 ga molds any more. He got fed up with it, and my 12 ga mold was the last one cut. He had to many problems he said. I know people who can cut one for you. I might even have a few slugs for you to try. I load all of mine with smokeless, but black would do just fine. The NEF is supposed to be a good solid action. Who is going to make the barrel, and the custom reamer for you? The brass cases will require a different chamber for best accuracy.

The LFN design will need more than 800 grains of alloy to cast. An 811 grain Whitworth style bullet with .525" Metplat is only .827" long with a .375" long nose. 12Ga bullets can get real heavy, when trying to design them. A WFN or LFN design will probably need 900-1000grains of WW alloy to be viable. The long noses use too much weight, and detract from the bearing surface.

Greg