Henry,
If it is impairing your vision, then it must be pressing on your optic chiasm. Good thing surgery is tomorrow. Godspeed.

Angular momentum of the bullet is only in the range of 1%, IIRC, of the linear momentum, and is usually negligible for most effects on the shooter, except for the torque of the rifle in hand. That is why so many of Saeed's "Champions" can't hold onto the rifle that twists to the right, unexpectedly, to them.

Faster twist effects on pressure and velocity, when going from a 15" twist to a 7.5" twist amounted to only a half percent change, according to some artillery testing.

And that brings me to keyholing Darwins that still shoot into 1.25" 3-shot groups at 50 yards with the lowly Mossberg 835 rifled bore slug gun:

First I tested some Remington 1-ounce Foster slugs that were supposed to do 1760 fps in a 30" test barrel.

I got three shots done and on the fourth the wad smashed the chrono. The slug would have produced more than this superficial wound at 15 feet:







Note you can see the fins on the Foster target holes.

Note that the Darwin was yawing a bit as it hit the target with better accuracy.

Upping the velocity will increase stabilization.
So would a 1:20" TWIST instead of 1:35" TWIST.
Bet these Darwins were way subsonic.
They kicked little.

The Darwin does have a wee bit of dart-stabilization, and the uniformity of these in weight is not so good from my first casting, but I will do better.

I did set up another disposable Chrony and got some more Foster readings by shooting the slugs closer to the screens so the wads had more room to pass above the chronograph.

I then tried the Darwin chronography as I shot those three shots above.

The Chrony got confused and gave these readings: 4129, 4376, ERROR

Apparently the shattered plastic over-slug disk, 2 fiber wads, 4 nitro cards, and the slug ... add up to quite a confusing swarm to the Chrony.

I will have to set the Chrony 50 yards from the bench, so the swarm gets left behind as the Darwin arrives.

I now call my Mossberg 835 "HMS Beagle" or just "Peanuts" for short.

Note how much lower the Darwin trajectory is than the Foster with the same scope setting. Subsonic and little muzzle rise = lower POI than a supersonic Foster with similar muzzle rise. 19 inches extra drop for the Darwin at 50 yards.

If I run out of scope adjustment, I can bend the cantilever mount up at the back to give some 1000-yard tilt to the scope base, and shim it.

I've seen that keyholing before and it was due to using the wrong BN hardness slugs. My bet is it goes away with Linotype darwins. Thanks for posting your results though very interesting. I gotta get a 835 and report some data with my brass cases.
Henry22LR - Godspeed man. Best of luck with your surgery. Our thoughts will be with you. -Rob

Rob,
I have a Lee sizer being made for .730".
Then I will be able to cast in Linotype.
Maybe the soft 30:1 keyholing will clear up with hard alloy. Hadn't thought of that. Thanks.

RIP-Rob- You got to shoot them faster and they will be stable.
Your only doing a grand or so with that load.
Your Darwins are tested, and I also, Praise the Lord, got my
RMC brass cases yesterday. I tested your slugs in NEF with
1 to 35 twist. They went into backstop straight.


Brass 3.5" RMC cases, close to top load and that still
good extracted good, got 1400 fps with your 1400 gr Darwin.
83gr of IMR 4227 - one .135" card- two 1/2" fiber wads.
Hairy load - 90 gr, same card/wads- 1500 plus.
Peak Pressures ranging about 20-24,000 psi.

With 3.5" used Fed plastic, top load that extracted good
was 1300 fps with the 1400gr Darwin. Used
71gr of IMR 4227 - one .135 card - one 1/2" fiber wad,
a .040 card over slug and star crimped case shut.
Peak pressure about 15,000 psi. basecup expanded from
.803" to .813", so that's limit I use
and it matches loads I had tested at lab showing
about 15,000 psi peak pressure.

I do chrono 45 ft for wads/sabots to get slug ahead of
them.On thin card over slug I glued it on so it would
stay with slug for reading The slugs were blackened with
black marker to get a readings as they are too
silvery otherwise.I use marker on all light colored
slugs and bullets. Ed

Ed,
Lots of good info there, thanks.

My turn is coming in the order pile, so it is great to hear that Dave Casey is making brass, like he said.

Do you think the Mossberg would be safe for that 1300 fps load with 71 grains of IMR-4227? 15000 psi?

I am sure it will be pleasant enough with the lead in the butt. My load was only 50 grains of IMR-4227, very gentle.

Will be lengthening the chamber of the NEF to 3.85".
Will get a Pac-Nor 1:20" with 1.75" shank and someday find a 50BMG action that can have the boltface opened up to 12Ga rim.

With 1400 fps, those 1400-grainers are in elephant busting territory in the RMC 3.5" brass.

When 3.85" "12GA SHOTGUN of Nevada, LLC" brass arrives, the 12GaFH will be in T. rex territory.

For the Mossy I'd stop at 65 gr, don't
want to split the muzzle. The Mossy would take
peak pressure ok at breech but don't know
how the muzzle would do with pressures our
slower powders have at the muzzle.
Maybe someday I'll get stuff to get setup
to put strain gauge on muzzle of guns
like Mossy, Encore, Ithaca, etc just to see
what they are doing with our type of loads.
I have 12ga ENcore here now, that I will test all
kinds of loads in comparison to NEF. It has a
one inch muzzle, but the breech ia only one inch,
where in comparison the NEF is 1.2" breech.
Base of 12ga case is .803".

The gun companies are frustrating to say the least.
Nef is thick enough but needs 4 more inches barrel.
Encore has long barrel, but should have heavier breech.
The Mossy rifled barrel has breech heavy, but be nice
to have one inch plus muzzle, the same for other rifled
slug guns, like Ithaca, Win, Rem..plus more length. Ed

Good grief Rob the Forums are going to crash from this thread! Just came back to being full out and about from a kidney transplant, good to see that you're still having fun with this project!

http://gardnerscache.com/12_gauge_sabot_slugs.html

Good luck you are all crazy.

Another good one.
http://www.dixieslugs.com/products.html

I've tested the Dixies and info is in previous
posts on this thread. I will test the Lyman's when
I get them. I have wads here for them.
I also have the new Ballistic Products hard
sabot coming. They will hold 300gr, 350gr, 500gr
XTPs .500 bullets, as well as many other .500 cal.
Getting a supply of hard sabots has been a real
long search for many shotgun guys, wanting to
reload their own, with their slugs, factory slugs.
their own cast slugs, etc. Without paying
3 bucks per loaded sabot round from big factories.
I'll test Lymans at speed, because many on other forums
are getting great accuracy.See what they do with
the shit behind them...

On testing the hairy load above, 90 gr 4227 with
1400 gr, 1500 plus, I finally got all the powder to
burn, no granules, burnt powder, or anything in the barrel
or cases.Ed

Rip/Ed-you guys want some Darwins made from brass?probabaly will weigh in at 1200grs for same dimensions.
Ed-90 grs at 2500 gps with 1400 gps yup that's a nasty load.-Rob

Rob,
A hard brass Darwin of 0.729" diameter would go faster, spin better, and eliminate any keyholing for sure, even in a 1:35" twist.
That would turn the lowly Mossberg 835 Ultimag into an elephant gun, even with 3.5" plastic hulls. Please do it, and put it on my account at 12Ga Shotgun of Nevada, LLC.

If you shoot it backwards it becomes a cup point varmint slug.

I wonder how much copper would open up? 1"

Copper can come later. Price of copper is coming down lately, I hear.

SD of 1200-grain brass Darwin = .3225728

I will be trying to chronograph again with the 1400-grain Darwin 30:1 slugs, from 50 grains to 65 grains of IMR-4227 ... shiney 30:1 blacked with a big fat indelible marker ... chronograph at 75 feet instead of 15 feet ... will have to correct to MV with assumed BC of 0.???

RIP-- Put a heavy block of steel in front of
chrono like I have, It is 8" wide and 2"
thick, and I have it on supports tilted back
at 45 degees. Nothing can hit the chrono
body. I've had wads hit the wires.Another thing I do
especially with wads,sabots, and plastic cases,
is to step out the door and shoot, no chrono,
until I get load that expands bases/base cups, etc
near the limits I have set. Then I chrono the
last couple loads levels,compare to formulas/chart.
Saves so much time. I don't have to travel to shoot
or chrono, just out the door, where my big slabwood
bundles are piled for a backstop.


Rob- Sorry, I mis=typed the top speed twice on the
1400gr using brass case.. It should read 1500 plus.
I changed it above. To get that to 2500,
I,d have to use Savage with real long case, big
primer, and 50k psi load. But better stock first.
I tested 1100gr solids John made me.
They come 750 gr hollowbase and I filled base
so they were 880gr , 1000gr, and top
at 1100gr. That's the one weight at
2600 that put a crack in my Savage stock.
The Darwin 1400 in the NEF really rocked.
If the NEF wasn't weighted it be real fun.
Thank God I write it all down for reference,
to correct all the mistyping, and mental blanks
I have while on the puter.Ed

Ed,
So you been there and done that, eh? And lots of that too!

Thanks for the tip on the chrony armor. I can rig something. Even 1/4" thick aluminum plate ought to stop a wad at 15 to 25 yards. Maybe a horizontal rectangle to protect the chrony and two angled vertical plates to make a V to run interference for the sky screen supports, and another horizontal member to block for the sky screens. Hacksaw, drill, nuts and bolts ... might even use some spare steel from the IWBB for another Erector Set job. The Chronies may graze in the Blackberry Patch alongside the Iron WaterBoard Buffalo. To live and die in the blackberry patch: There are worse fates for a Chrony.

I knew I would someday find a use for the aluminum plate tucked away in the garage.

I'll be back in Vegas saturday and will write a pgrm for some Darwins. You guys have done so much load development I need to repay the effort and hard won info. Been watching the price of copper and will buy a few 12 Ft lengths of 7/8 once I think the price has bottomed. One 12 ft 7/8 rod will make about 500 12GaFH Rims! I'll load up on Brass too! One thing to remember is ER Shaw made and hopefully still makes 12Ga rifled barrels that are 1.2 inch at the breech and tapering to 1" at the muzzel. I have one that I was saving for a 12 Bore Martini Henry or a farquarsen action. I always thought about TIG welding on a Encore barrel lug and seeing if I could make that work. RIP go for the 3.85 full case. PM me when you get a chance.-Rob

Rob: PM sent.

ED- What can I do to help?-Rob

ED/RIP- I spent some time making some 3.5 inch cases. The brass is so thick that the only wasy to load a bullet is with a expander die. Not a big deal but a extra step. I am hesitant to turn the inside of the case if you guys think that a std 12Ga 3.5 inch chamber will cause further expansion. Ed what are you using for a sizer? I made a had die for my FL 3.5 cases and may need to make another for these shorter guys. Once we work this out and if there is enough demand I can make a full set of dies and expanders for all the versions.-Rob

Yes you want to leave the cases thick when
you cut them back to 3.5", to fit regular
chambers closer. The brass thickness of the
RMC 3.5" is .030, and cases I've cut back from
ours about .020. The RMC goes into to regular
chamber fine, so there is still plenty of
clearance with our cut back. I cut up an old
12ga Hollywood die set that I use to size
both our cases and the RMC cases. I have 5 pieces and they range in size, to do the thick
down to the thin cases so that bullets always fit. With the bases same on both.Ed.

Rob,
What Ed said is my preference too.

I have some fairly worthless RCBS Cowboy 12Ga dies.
I was figuring to cut up some 50BMG dies and grind and polish some homemade implements, until I coud get some custom dies made.

If you can make dies for full thickness, full length brass, I would just as soon buy them from you, and anything else you might come up with, of use for any length brass up to 3.85".

There is a source for 12GaFH chamber reamer: Dave Kiff, PT&G

Source for .730"/1400gr Darwin Slug mould: Brooks' Tru*Bore Moulds

Coming soon: LEE PRECISION .730" lead bullet sizer

.729-caliber barrel sources: Pac-Nor and more

Sources for BRASS:
3.85" and shorter: 12GA SHOTGUN of Nevada, LLC (dba NohBohzo, Inc., Robgunbuilder, etc.)
3.5" and shorter: RMC

A source for reloading dies: ???

A source for nice, big, strong, falling block action for 12GaFH: ???

For now my 12GaFH 3.85" will be an NEF Ultra Slug.

RMC Care Package arrived 10/24/08:

Just how thick are those RMC cases? From the pics my fears about the .50 BMG cases are unfounded. Nice looking stuff.reminds me of the first .600 ok brass I used to make. If I get a chance Ill post some pics of my reloading dies. Mine are for a RCBS ammomaster.-Rob

Rob,
Please do show us some dies that fit the 1.5"x12tpi hole of the AmmoMaster.

Ed has been telling us that the RMC brass is about 0.030" wall thickness at the mouth.

I measured mine hastily and here is what I get:

2-5/8" brass for use in 2.75" chambers:
mouth wall: 0.032"
O.D. at mouth: 0.795"
I.D. at mouth: 0.731"
base O.D. = 0.808"
rim diam. = 0.870"
case length = 2.632"

2-7/8" brass for use in 3.0" chambers:
0.032" mouth wall
0.795" OD
0.731" ID
0.808" base
0.870" rim
2.878" OL

3-1/2" brass for use in > 3.5" chambers
0.034" mouth wall
0.798" OD
0.730" ID
0.809" base
0.875" rim
3.502" OL

The ID of the case mouths on the shorter brass is 0.731".

The ID of the case mouth on the 3.5" brass is 0.730".

Seems perfect for use with the Darwin slug and the Dave Kiff 12GaFH reamer.

Ed,
John Riley Buhmiller used to throw an extra primer into the bottom of his rifle case then cover it up with a charge of slow powder, back in the 40's and 50's when primer potency was not so good.

Regarding RMC cases with 209 primer: Are we stuck with 4227 and wads, or could some duplex load be used to ignite a case full of H50BMG or other slow powder?

My idea for the NEF is to get a 1400-grain Darwin up to 1400 to 1500 fps using either RMC 3.5" brass or Rob's 3.85" brass. Rob's brass with 50BMG primer is no problem. My shoulder will be the limit there.

You may have covered 12GaFH duplex loads already, but it may take a while for me to dig it out of this thread ... The 12GaFH Thread FH ...

The 4227 will get you 1500 in a NEF(but its got to
be weighted), using RMC brass with shotgun primer like I did.
With RMC cases Duplex loads are best with 15gr of Blue Dot
and using RL-19 for 1400gr. RL-15 for lighter slugs,
with 10gr Blue Dot. But it is still easier w/slow powders, with
brass with big primer. Now that kit you got with cases will
do for moderate loads where no resizing is needed. When I get
RMC cases up in pressure they need slight resing above the
long corner radius, shown in the pic of our and RMC
sectioned. It is strong for a turned case.Our case on the left RMC
on the right and its base is thicker than ours a little.
Oh, My resize dies fits the 1.5" ammomaster top. Ed

Home from the hospital after a very successful surgery. Tumor benign, and they were able to leave a normal amount of pituitary to maybe restore normal function. My head is still full of "packing" which will be removed Monday in the Ear, Nose and Throat doctor's office. Eyes working both together, no more double vision.

I should be able to present the user-friendly dart-stability program in a couple of weeks, now...

Good news Henry. Take it slow, there is no
hurry on this stuff, as we been doing it
for years.Ed

Thanks Ed. I’ve been using the user-friendly dart stability program as a time-passer in the lonely, dark hours anticipating uncertain surgery. It is mostly written now, in my head, but yet to be fully transcribed into BASIC. My Physics training makes my mind a friendly, orderly place to spend leisure time, even in the dark…

A speedy and full recovery to you Mr. 22LR

Henry22lr. Best wishes for a speedy recovery. Sounds extremely positive and we are all very happy for you!
ED/RIP- Sounds good. BTW do they make the Mossberg 835 in a left hand version. I saw one today but it wasnt the slug version.
Finally, I learned my lesson with slow powder and primers(BTW a big case hangfire is a impressive incident to experience OUCH) and that was a major factor in using the .50BMG case. Wonder if the Mossberg 835 can pop one though stock. Worst case is I have to make a stronger firing pin spring. Intewrestingly the Encore didnt need one. No big deal as I am pretty good at making springs.-Rob -

Henry22LR,
Way to go!
Soon you will be feeling like Hank220Swift.
Let's just hope your IQ has not been improved.

Rob,
The 835 Ulti-Mag has ambidextrous tang safety, trigger, pump, and loading port. So what if it ejects the hulls into your right breast pocket, and you are stuck with the ambidextrous standard stock? The standard stock will hold even more lead than the thumbhole stock, and fifty bucks will replace it when it breaks off from Darwin Fatigue.

One thing I have noticed is the shell lifter has trouble getting a nose-heavy 1400-grain slug 3.5" load lifted as it is pumped from the magazine. I rotate the action 90 degrees (gangsta style) as I close the pump to negate gravity, and it loads smoothly.

Ed,
Thanks for saving me a sectioning of the RMC brass. Gotta say that turned brass is built like a brick dunny.

Yes- Turned brass looks good but they have definite pressure limits. I never took the .600OK cases I and Fritz 454 made over 36KPSI. It really showed expansion changes and rapidly work hardened. Eventually the primer pockets got so loose a primer would not stay in. In comparison the .50BMG brass is good to 65 Kpsi or more and I have competition cases that have been fired over 20 times. Just a word of caution.-Rob

First RMC 3.5 inch case now has 25 firings
on it, These are max loads about 25,000 psi
in NEF. Now RMC makes them so base of case
fits regular chamber tighter than other
brass cases or plastic cases.
He makes them .808" --That cuts down
on expansion and difficult resizing.
For our cases chamber base should be .805"
at base(regular is .811")- mouth should be
.780"( regular .800"). And properly sized
2.75" plastic cases and the 12ga brass
Magtech cases still chamber and fire ok..Ed

Ed,
Glad to hear the RMC brass lasts forever.
They should easily survive being made dummies of, and live on to fire Darwins and whatnot.

Rob's brass should handle the higher pressure loads, and whatnot projectiles forever too.

Eye candy for 12 Gauge Afficionados:



L to R: (COL, slug/shot/load, hull length/type)

1. 3.058", Darwin, 2-5/8" RMC
2. 3.308", Darwin, 2-5/8" RMC
3. 3.248", Darwin, 2-7/8" RMC
4. 3.584", Darwin, 2-7/8" RMC
5. 4.145", Darwin, 3-1/2" RMC
6. 4.215", Darwin, 3.85" 12GaFH
7. 1.375", 3.25 ounce Darwin, no hull
8. 3.090", 2.25 ounce No.5 shot, 3-1/2" Win. plastic
9. 2.595", 1 ounce copper sabot, 3" Rem. plastic
10. 2.340", 1.5 ounce No.4 shot, 2-3/4" Rem. plastic

RIP- Very cool pics! I am setting up the machines to make rims today and will try and pgm for the Darwin slug tomorrow. Unfortunately I'm practicing for a advanced Combat pistol course and its taking too much time.
Hey guys we are closing in on 50K views on this thread. That will be a NEW RECORD!
Gives one a sense of the degree of interest in the 12GaFH and its younger siblings.-Rob

The 12GFH is looking better every day.

quote:

Originally posted by Robgunbuilder:
RIP- Very cool pics! I am setting up the machines to make rims today and will try and pgm for the Darwin slug tomorrow. Unfortunately I'm practicing for a advanced Combat pistol course and its taking too much time.
Hey guys we are closing in on 50K views on this thread. That will be a NEW RECORD!
Gives one a sense of the degree of interest in the 12GaFH and its younger siblings.-Rob

Cool.

The 12Ga got me started in life ... raised on shotguns ... country boy can survive ... favorite popgun since I was 8 years old.

.729/1200-grain brass Darwins (SD = 0.323) at a measley 1500 fps have a TKO of 187.
Compare this to the TKO of a .375/300gr @ 2530fps: 40.7

Even an NEF rechambered to 12GaFH will knock out an elephant.
And we all know from the 45-70 lore that a nondeforming slug at a mere 1400 fps penetrates forever ... as you were ...

How fast will a .729/1200-grainer go from a 12GaFH 3.85" in Rob's Borchardt with BMG brass?

2150 fps.
TKO = 269
Extreme overkill.