12 Bore Schrifle project

Did you state the magazine capacity?

Hogpatrol said:

Have you considered a veggie or wool wad on top of the powder?

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There are 2 nitro cards and 2 x 1/2" veg. Fiber wads pressed down on the powder. When i use the brass cases i still get a round that sounds more like a rocket than a gun. New roll crimped loads look like this

It is 2 rounds in the mag and 1 in the chamber. More than enough for a close range bear gun!

crs said:

Did you state the magazine capacity?

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Short update... So I got out today to try out some of the loads in the plastic shells. Surprising how little data there is out there for a nearly nearly 2 oz. round from a 12 gauge shotgun hull. I had to extrapolate a lot of it. I read about Ross Seyfried's exploits trying to duplicate the H&H paradox load and he had a 21.5 grain charge of Unique from a cheddite hull with a 730 grain bullet in a rifled paradox gun. I have a 775 grain so I used those and then loaded some light (as it turned out very light) blue dot loads extrapolated from 3" 1-7/8 oz. shotshell data from Alliant... These are not intended as load data and was extrapolated without pressure testing so if you want to duplicate it, do so at your own risk... anyway...

here are the results:

20.0 Grains Unique
Fiocchi 3" hull
Roll Crimp
2x 1/8" Nitro Cards - Waxed
2x 1/2" Veg fiber cushion wads
775 grain hardcast Wadcutter

Avg. Vel: 722 fps
Muzzle Energy: 897 ft.-lbs

28.0 Grains Blue Dot
Fiocchi 3" hull
Roll Crimp
2x 1/8" Nitro Cards - Waxed
2x 1/2" Veg fiber cushion wads
775 grain hardcast Wadcutter

Avg. Vel: 752 fps
Muzzle Energy: 973 ft.-lbs

30.0 Grains Blue Dot
Fiocchi 3" hull
Roll Crimp
2x 1/8" Nitro Cards - Waxed
2x 1/2" Veg fiber cushion wads
775 grain hardcast Wadcutter

Avg. Vel: 825 fps
Muzzle Energy: 1,171 ft.-lbs


Still not where I want to be but we're making progress!

Looking at those shells, my guess is a: too many wads and b: gasses are getting by them. It's a hell of a subsonic load though! Maybe solid wads only with the gun strapped down in lead sled and take cover, then pull the trigger by using a piece of string.

Hogpatrol said:

Looking at those shells, my guess is a: too many wads and b: gasses are getting by them. It's a hell of a subsonic load though! Maybe solid wads only with the gun strapped down in lead sled and take cover, then pull the trigger by using a piece of string.

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The gases getting by them shouldn't be an issue once the bullet gets into the barrel. My bullet is 0.003" over groove diameter so the bullet should seal the bore solidly. Or do you mean while it's in the shell before it enters the barrel? Would applying more pressure to the wad help build more pressure?

harking back to black powder again.
when we shoot bore diameter bullets, often in a chamber for groove diameter bullets, we rely on wads to for the initial seal until the bullets bump up and seal in their own right.
smokeless will bump up bullets less than black.
wads we use are mostly veg and or ldpe.
ldpe in particular swell under the pressure of firing and seals well.
felt wads 0.010 to 0.020 over groove diameter also seal, particularly when soaked in lube.
gas blasting past lead alloy bullets will cut them, causing the worst kind of leading possible.
if they do not seal in the case, it is too late to worry about sealing the barrel.
bruce.

bruce moulds said:

harking back to black powder again.
when we shoot bore diameter bullets, often in a chamber for groove diameter bullets, we rely on wads to for the initial seal until the bullets bump up and seal in their own right.
smokeless will bump up bullets less than black.
wads we use are mostly veg and or ldpe.
ldpe in particular swell under the pressure of firing and seals well.
felt wads 0.010 to 0.020 over groove diameter also seal, particularly when soaked in lube.
gas blasting past lead alloy bullets will cut them, causing the worst kind of leading possible.
if they do not seal in the case, it is too late to worry about sealing the barrel.
bruce.

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What I can tell you is that I get zero leading issues. I have fired roughly 20 of these rounds through this bore and have no leading at all. I have lots of experience with casting and experimenting with tens of thousands of pistol bullets various calibers and was expecting some leading. I was pretty excited when there was none which given the fact that the bullet is hard cast and the pressure is so low indicates to me that there is a good seal behind it. Normally, low pressure and hard cast bullets = heavy leading.

ChrisG said:

The gases getting by them shouldn't be an issue once the bullet gets into the barrel. My bullet is 0.003" over groove diameter so the bullet should seal the bore solidly. Or do you mean while it's in the shell before it enters the barrel? Would applying more pressure to the wad help build more pressure?

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Yes, gas getting by the wads in the shell, thus losing pressure.

Chris, I've never loaded cast bullets in a rifle. I was just wondering is there a "gas check" available in 12 Ga.? Would it be of any practical value? This project of yours is "way outside my box" and I am just curious.

Shootist43 said:

Chris, I've never loaded cast bullets in a rifle. I was just wondering is there a "gas check" available in 12 Ga.? Would it be of any practical value? This project of yours is "way outside my box" and I am just curious.

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I don't think so. A gas check would only serve to keep hot gases from cutting into the base of the bullet and I am currently not having that problem as I am getting no leading. Plus i have no way of affixing one. Lyman doesnt make a .732" lubrisizer die, and it wouldnt even fit in the lubrisizer i have if they did. I may, however need to incorporate a plastic 12 gauge gas seal into the wad column as @Hogpatrol recommended that gas is seeping by the nitro cards and causing a loss of pressure before the powder can really get going. I will give that a try and see if I get some more speed from it.

12 gauge gas seal selection:

https://www.ballisticproducts.com/12ga-Obturator-gas-seal-250_bag/productinfo/02012/

Hogpatrol said:

12 gauge gas seal selection:

https://www.ballisticproducts.com/12ga-Obturator-gas-seal-250_bag/productinfo/02012/

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Its funny you sent this... I actually already ordered the X12X Gas seals from BPI like 10 minutes before I saw this. Is there a tremendous difference? and in your opinion, what kind of velocity gains am I looking at by incorporating a gas seal into the wad column? I am liking Unique because I use so little powder to get the velocities I am getting with 8 grains more Blue Dot while still maintaining lower pressure. According to others loads (Ross Seyfried among them) that have been pressure tested my loads should be less than 8,000psi and they sure sound like they have very little pressure. But I may move to Blue Dot exclusively as it is designed for heavy loads. I was using 30 grains but will likely step up to 32 grains to see if I can break 1000 fps with a gas seal.

I am pretty sure one of those 775 grain boulders at 800 fps would still flatten a black bear but I want them to shoot flat enough to get out 75-100 yards without a tremendous amount of holdover. so I am still looking for that magical 1,100 to 1,200 FPS. If I can't do it with Blue Dot, I may start where I left off with blue dot charge weight and work up a 300MP or H-110 load that produces those speeds, then send them off to get pressure tested. This website says that it is $40 to pressure test a 5 shot string or $25 a string for 2 or more shot strings. I think that is TOTALLY worth it once I find a load that I like.

ChrisG said:

Its funny you sent this... I actually already ordered the X12X Gas seals from BPI like 10 minutes before I saw this. Is there a tremendous difference? and in your opinion, what kind of velocity gains am I looking at by incorporating a gas seal into the wad column? I am liking Unique because I use so little powder to get the velocities I am getting with 8 grains more Blue Dot while still maintaining lower pressure. According to others loads (Ross Seyfried among them) that have been pressure tested my loads should be less than 8,000psi and they sure sound like they have very little pressure. But I may move to Blue Dot exclusively as it is designed for heavy loads. I was using 30 grains but will likely step up to 32 grains to see if I can break 1000 fps with a gas seal.

I am pretty sure one of those 775 grain boulders at 800 fps would still flatten a black bear but I want them to shoot flat enough to get out 75-100 yards without a tremendous amount of holdover. so I am still looking for that magical 1,100 to 1,200 FPS. If I can't do it with Blue Dot, I may start where I left off with blue dot charge weight and work up a 300MP or H-110 load that produces those speeds, then send them off to get pressure tested. This website says that it is $40 to pressure test a 5 shot string or $25 a string for 2 or more shot strings. I think that is TOTALLY worth it once I find a load that I like.

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May have missed it but what primers are you using? Mag or standard? With that short of a powder column, I'd go with standard. I'm still leaning toward the gas seal helping. I would definitely go for the pressure tests.

Hogpatrol said:

May have missed it but what primers are you using? Mag or standard? With that short of a powder column, I'd go with standard. I'm still leaning toward the gas seal helping. I would definitely go for the pressure tests.

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I am using Fiocchi 616 primers. I actually got Fiocchi not Cheddite hulls and that is what Fiocchi and Alliant Recommend. They are definitely not magnum primers.

So I got the gas seals in the other day. I loaded up 5 rounds. 3 with 20 grains of unique and 2 with 30 grains of blue dot. Wad column is the same but with one of the nitro cards removed because of the space taken up by the gas seal. I'm going to chronograph them this weekend and see if the gas seal makes a difference.

Just read the whole thread. Crazy ideas abound but I like the concept.

Two issues I don’t like:

1. The bullet is way too heavy, but you need performance and volume. Have you thought about copper, brass, or a sabot so you can shoot something with good volume/size, but at around 437-450 grains?

2. You cut the barrel to 18.5”. How many powders will actual combust and build pressure completely over such a short distance? Have you considered that the faster burning powder necessary will produce higher pressure over shorter distances, perhaps unsafely?

rookhawk said:

Just read the whole thread. Crazy ideas abound but I like the concept.

Two issues I don’t like:

1. The bullet is way too heavy, but you need performance and volume. Have you thought about copper, brass, or a sabot so you can shoot something with good volume/size, but at around 437-450 grains?

2. You cut the barrel to 18.5”. How many powders will actual combust and build pressure completely over such a short distance? Have you considered that the faster burning powder necessary will produce higher pressure over shorter distances, perhaps unsafely?

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Hi rookhawk,

Thanks for your concern. I will do my best to stress your concerns.

The marlin has a tremendously thick barrel compared to most shotguns and a half inch thick locking lug... It is a tremendously strong gun.

1. The bullet itself is only 25 -50 grains heavier than a westley richards explora load or a h&h paradox. Dixie slugs has routinely loaded slugs (really just big bullets) up to 1,000 grains in a 12 gauge. A 450 to 500 grain bullet at .732" has the sectional density of a tennis ball. Thats why I didnt want to use one of those.

Ross Seyfried has loads up to 1,200 grains I believe and his 750 grain mild load was 21.5 grains of unique for around 7,000 psi. I wanted a heavy bullet for short range. I am looking for weight and impact rather than flat shooting trajectory. 1,100 fps is completely doable with a bullet of this weight. Dixie got their 1,000 grain slug to like 950 fps and pressure was still less than 10,000psi.

2. All powders are fast. The slowest rifle powder in the world usually takes no more than a few inches to burn completely and peak pressure is reached right near the chamber. That's why the barrel is so thick there.

In shotguns, barrel length has little to do with exterior ballistics once you get past about 16" because the pressure is already so low and drops to almost nothing shortly thereafter. A 18" shotgun barrel with slugs produces only 50 fps less than the same load in a 24" shotgun barrel. People often mistake the fireball at the end of the barrel as unburnt powder igniting in air but it is actually the gases which are the byproduct of the consumed powder igniting on impact with atmospheric oxygen, if the pressure at the muzzle is high enough to produce a shockwave which ignites the gases. The military has known this since the 30s, yet the myth of powder burning all the way down the barrel persists. All the powder is long gone by the end of even a slow burning charge in a short shotgun barrel if the powder is designed to burn completely at low pressure.

As to the faster powder... I was just going by Ross's load and playing it safe. I will probably end up using blue dot as it is designed to burn completely at shotgun pressures and it is slow enough to give good speed. In almost all cases the fastest load is always the fastest load regardless of barrel length. The higher remaining pressure at the end of a short barrel and increased volume of gases produced by large charges contribute to the flash issue.

So far I am having issues even getting enough pressure to get the powder (even blue dot) to burn completely. Even getting 800 fps with the load. I am hoping the gas seal corrects that issue. I have learned a lot about shotshell loading throughout this project. Enough to know that a lot of the metallic reloading concepts I know don't apply and the challenge thus far has been to PRODUCE enough pressure... not reign it back in. It has been a real learning experience, but one where I started the loads ultra conservatively and have carefully adjusted one component at a time. Once I get the velocity I am looking for, I am going to send them off to be pressure tested.

Hi @ChrisG

Thanks for the info as you've clearly given it some thought.

My knowledge starts and ends with custom savage slug rifles since I live in a slug-only state and have built 5-6 of them. I had assumed the powders would be less efficient with the 18.5" barrel only because my 22" guns have a lot less velocity than the 24"-26" custom barrels with saboted slugs.

Anyway, I still go back to the bullet weight. I understand you want the VOLUME that the bullet provides, but do you want to slow the bullet down that much? Wouldn't a lighter-than-lead alternative get your velocity up a bit and still have incredible stopping power? (copper/brass)

The great thing about your schrifle project is that you are handloading. The one thing I found in my research, and custom builders also found, is that free-bore headspace is a HUGE ISSUE for accuracy. The great thing about your custom setup is you can buy 3" or 3-1/2" hulls and trim them back to whatever is optimal freebore for your slug before it hits the rifling/forcing cone. I guess I'm saying that I think you stand good chances of having great accuracy from your load development for this reason.

rookhawk said:

Hi @ChrisG

Thanks for the info as you've clearly given it some thought.

My knowledge starts and ends with custom savage slug rifles since I live in a slug-only state and have built 5-6 of them. I had assumed the powders would be less efficient with the 18.5" barrel only because my 22" guns have a lot less velocity than the 24"-26" custom barrels with saboted slugs.

Anyway, I still go back to the bullet weight. I understand you want the VOLUME that the bullet provides, but do you want to slow the bullet down that much? Wouldn't a lighter-than-lead alternative get your velocity up a bit and still have incredible stopping power? (copper/brass)

The great thing about your schrifle project is that you are handloading. The one thing I found in my research, and custom builders also found, is that free-bore headspace is a HUGE ISSUE for accuracy. The great thing about your custom setup is you can buy 3" or 3-1/2" hulls and trim them back to whatever is optimal freebore for your slug before it hits the rifling/forcing cone. I guess I'm saying that I think you stand good chances of having great accuracy from your load development for this reason.

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I can definitely see where a saboted 300 or 325 grain bullet would definitely lose a bunch of velocity due to a shorter barrel. As bullet weight goes up, loss per inch of barrel goes down. I chronoed a standard 1 oz slug out of the original 21" barrel before I chopped it. I was getting 1,560 fps. With the 18.5" barrel that 1 oz foster slug was moving around 1520fps. In fact SD is greater than that... So I didn't lose a ton and my bullet outweighs it by more than 300 grains. 1,100 fps will be absolutely fine for where I hunt around here. Shots seldom go farther than 75 yards with the vast majority being 50 or less. 1,100 fps is plenty flat shooting on a deer or bear out to 100 yards or so and when it gets there, my slug will still be moving over 900fps with about 1,400 ft -lbs of energy. I would personally rather be able to cast my bullets. I can cast probably 25 of these for the price of having one brass turned for me. Plus a lead bullet has an advantage in sectional density and penetration.

I am loading these in 3" hulls and I roll them back until the crimp just clears the inside of the magazine (about 2.70") and the gun feeds them great. I haven't checked freebore but it is a 3" chamber so I assume the forcing cone is right around 3 inches into the chamber.

Any insights are a welcome addition. I have a lot to learn about slug guns. I imagine you have quite a bit of knowledge as you build them and hunt exclusively with them in state.