quote:

Originally posted by FOOBAR:
Whoever does it needs a LONG milling table AND an accurate rotary table and/or CNC.

I'm wondering how the bullet will react with the interrupted rifling??? Will it affect accuracy or not??? Something to think about.

Good Luck on your project.

A brake with convoluted angled vents is best made on a 5 axis VMC or even better - a large lathe with CYB axis and barfeeder ...

These guns have high muzzel pressure so BIG Holes to dump the gas will work best. Impressive axial fireballs when fired at night!-Rob

Thanks all...for the insights.

Ed...I will just put that slick laminated stock on my NEF 6mmBR/17FB switchbarrel frame and call it good...maybe put some non-skid tape on it also...I've almost finished the walnut thumbhole stock shaping and will do an epoxy skim bed on the stock lock joint...

I'm also thinking about drilling out the bolt hole, threading the frame end portion of the stock, turning off bottom part threads and epoxying in a piece of 9/16 allthread to stiffen up that wrist area...

I plan on leaving the grip area slightly rough and stained only and finish sanding/staining/polyurethane danish oiling the rest over time. A day at at time and let the imagination run loose...

Most of the brakes I use are inside turned to thread OD size except for the end hole being roughly 0.010-0.040" larger than bore diameter...I try for 0.020"...supposedly anything over 0.040" and the brake starts loosing efficiency...just what I've read, I don't have any way of actually testing that theory, but someone has.

Macifej...I can get 5 axes with my mill...
X, Y, Z, tilt and spin...but not very easy...I could get the 6th axis if I figured out a way to hold the spin index and tailstock on a plate and in my rotateable vise, but the mill is WAY too wiggly to keep any solid foundation. I did a mockup yesterday out of 1.5" AL, 30° tilt and needed too much tool overhang or I would hit the index jaws when I spun it...I did several holes with varying levels of success, too much flex in all directions to do anything but one axis at a time...the effort did answer some questions and show me the problem areas to work out solutions for...but I will persevere if only for the possibility of random chaos.

Rob...I fired off a couple of 730 Terminators copies with the "Panzerschnozzle" in place and it didn't help a bit...lost about 1.25# of weight too boot...those loads definitely put the "oooohhhhhhccchhhschyte" on me. I checked every shop in town for RL-17 and it isn't listed as available in anyones vendors...so....RATSCHATTT again...at least I picked up a Limbsaver grind-to-fit recoil pad.

Time to do some redesigning, reverse the head tilt and shallow up the angle to 20° and try again...

This project is turning into one of those "almost/except" thingys...I can ALMOST copy that narly "sharkgill" of Gibs...except I can't get all the right angles setup...I ALMOST won the lotto...except I couldn't get all six numbers on one ticket....I ALMOST married the girl of my dreams...except she was ONLY in my dreams...I ALMOST won the Grand Prix...except Mario wouldn't loan me his Formula 1 racecar....

Enjoy your toys...Hahahahahaha

Foobar- Wait till you strat lighting off those 1085 gr darwins over 240gr of H50BMG or 225gr of Rl-25. That will get your attention, but its really not that bad. I've shot a whole lot worse fer sure! My gun still has the original stock and no added weights and nothing has broken yet. I'm glad your having lots of fun!-Rob

I think I will paint on my boony stripes, get on my ghilly, and do a slow slither up on those loads...not that I'm skeerd or limp wristed or any of that... Hahahahahah

Enjoy your toys

Foobar- They are not that bad. I actually want someone else to confirm that. I'm thinking no more than 100ft-lb recoil level. Gun runs outa barrel length and the ability to burn that much powder well before the recoil level gets too obnoxious. I'm gonna get some night fire pictures that will be very impressive.-Rob

The contestants are....



The one on the right is upside down...20° angle on the 1/2" side ports...kinda like Gibs???...that one looks like the port angle is at least 30°. I swapped ends with this brake and left the setup so I will try cutting the angle at 30° tomorrow. I fired one round apiece, 750 gr slug - 75 gr 4759 - 3" rem case -~1300 fs, with the two brakes...didn't feel much difference...powder residue clear out to the end holes...look close at the picture and you can see it in the bottom of the cut.

Recoil is coming mostly from the slug and powder weight...the brake isn't doing much I don't think...calculated is about 58 ftlbs and it feels close...I will go up to 80 gr 4759 tomorrow... which I preciously chrono'ed at 1575 fs with a 730 Terminator and my 7.5# Mossy 500 24" smoothbore...and see what it chrono's and how it feels. That one ran about 95 ftlbs recoil, the barrel went straight up and jumped out of my right hand...couldn't hold the slick woodstock grip... maybe I can hold this thumbhole grip a bit better, plus the extra 1.5 lbs will have some effect.

Thumbhole with pad and barrel with "notsosharkylooking" sharkgill brake. It's coming along.

Foobar
The faster the projectile gets the more effective the muzzle brake will become. At 1300fps its not even tickling the sides. Just remember, no ports facing down, top ports at least ~40/50% in area to side ports and it should do nicely. What you after idealy is ports that dont bleed to much to the sides that the top ports have no effect, but you still need the side ports so that the top ports dont overly push the barrel down (not good if its on a bipod or benchrest or even off hand) and the side ports have enough gas passing through to pull the firearm forward to minimize recoil. Its a delicate balancing act. See the top ports cant be reward facing since this will direct gas towards the shooters face, not nice. Now the other option is to cut the side ports higher towards the top of the brake to give a 20°/30° upwards angle and form a V shaped pressure front and do away with the top ports entirely. The should give a double down wards push from both side ports as well as a forwards pull but still keep the gas clear of the shooter. Mind you I dont think anyone standing close by will be impressed.

However I still think going with 3 distinct port constructs is best as you simplify the amount of difficult angle milling that is required.

Have fun.

Yeah...I'm no rocket scientist...the ones I've cut just dump the gas and don't really provide any "jet" effect. I've been "rough calculating" the areas of the top and side vents trying for as large a vent area as possible.

The last "sharkgill" was ~.550 sq in for the top and ~4 sq in for the side vents... just "slightly" upside down for a 50/50 ratio . The next one I will try to follow your 50/50 advice...one problem will be to get that ratio AND a 5 to 1 ratio like the Vias brake(or as high as I can) which has 48-3/8" holes and is about 5.25 to 1 ratio.

I roughed out the vent size on your picture at .500 x 1.25" which equals 5 sq in...I measuered the vents on my monitor screen at 1 x 2.5" and guessed at the actual measurements by roughing out the rest...by that ratio the actual MB would be about 1.4" OD and 4.75" long.

Basically trying different designs to see what happens and also seeing if I can figure out how to setup the mill.

I have a few more designs to try... a "sharkgill" with 1/8" to 1/4" wide side vents and 1/4" to 1/2" top vents...I will start on the small side first...and use the same MB to keep the turn around time to a minimum.

I will be using the 80 gr 4759/750 gr slug/3" load which will give me a good indicator as it is up near 1600 fs...still not a lot of gas production with this amount of powder relative to the size of the bore...be nice to have a hi-speed camera and a way to hold the rifle to measure the recoil and muzzle rise.

I will also toss in a series of 1100+/- gr slugs and RL-25/H50 BMG in 3.5" cases along the way...to see if the larger amounts of powder are really providing a higher gas effect...

Anyone ever see a gas volume per unit for the different powders by and chance??? It would be nice to know how much gas volume is produced by a gram of powder.

Enjoy your toys.

Foobar:
The picy I put up is a MB off a .50Cal rifle if thats of any help. I know it will produce a far greater effect than what a 12GFH will atm, but its still basicaly a sound starting point. I think you idea of starting the ports on the small side to start with is a good idea, Work your way up untill you hit a sweet spot. Mind you it will change a bit with different loads so it may have to be done with your final full reload that your going to be using most of the time. Just dont forget to keep the top port total area either the same or slightly smaller than the side ports. If there kept smaller at the start they can always be made bigger, bit harder to do the other way around.

Ed/Rob
I was just poking around on the net and I came across a reference to a C307 CCI primer thats ment for large bore BP firearms, Its basicaly a 209 primer but I have no idea if its hotter or colder. Just thought I'd throw it out there and see what you guys think.

Gibs...The caliber is good to know...gives some perspective to the size relationships.

Still more questions answered today...basically eliminated the 3/16 slots with the endmills I have...way too much bounce and flex in the setup at the speeds I have available, to cut a true slot/hole...

I think I'm trying to re-invent the wheel using a round rock and a sharp bamboo stick to cut it with...not quite spinnin' my wheels but close to it, plus I need to change the order on a few operations to see if that might help, make another 3MT center x 1.125" OD, and go to 25° for tool clearance. A few more tries and I will have enough "fun", use the "swirly" one and call the game...can't make a machinist out of a junk yard dog anyway...

I made a small chart to keep the calculation time shorter.

I'm heading out to smack some rats tomorrow...time for a change.

Enjoy your toys

Rob has been busy.
I have an excuse to resume shooting.



Nohbozo Darwin weights to nearest grain:

Aluminum: 346 gr
Brass: 1087 gr
Copper: 1149 gr

Rippalloy No. 2 Darwins: 1372 gr

30:1 Lead/Tin round ball of .735-caliber: 571 gr

The 209 type primers designed for BP mostly inlne
muzzle loaders have less explosive force and a little
more flame, to ignite black powder and substitutes.
Without prematurely moving slug in barrel before
powder gets ignited and going good.
This is my understanding of primers like C307.

General primer info.-- The firing pin blow sets off the
30 to 40% of the mix in a primer cup that is a shock
sensitive compound........Like lead styphnate.
Usually the mix has from 40 to 55% of an oxidizer
like barium nitrate and 4 to 12% of a reducer or fuel
like antimony sulfide. These two make the heat and flame
and add to the explosion that the styphnate got started.
Now by varying the amounts of these three they can get
moderate primers, 20% stronger primers they call magnum
primers, and real hotshot ones like 209 industrial primers
I took out of kiln cases and tested 12ga loads with.
There is alot of power levels and flame amounts they
can get by just changing percentages and chemicals,
as well as total amount of mixture in the cup,
all from the same size 209 primer cup.
Or any rifle, pistol, boxer, berdan primers.Ed

Foobar:
No worries matey, Rome wasn't built in a day, but it nearly burnt down in one. Take a breather, clear the old noodle, you never know insperation may come.

Rip:
Well why you sitting there chatting to us lot for, get busy matey - we want to see lots off Ka-BOOM shots from you.

Have fun matey.

Ed:
So I take it that the C307 is a no go then. Oh well, one more bit of info on the do's an don't's is always good. Thx matey.

I want to hear more shootin tales now!-Rob

http://www.gunsinternational.c...EF2-40A7E8B6612765A2

a nice double rifled 12 bore

anyone got 14K???

Hey... .729" copper spheres would be right about 500 grains and could be a great pre expanded DG ball. Shoot those puppies out fast!!!

Glad to see the aluminiums still in circulation... dont forget to melt them down and recycle

Hey... Rip... can you place a threaded hollowed out aluminium darwin in your lead mold, pour in some hot lead and make it a non deforming solid???

Question on barrel inserts...

so you need about .125" of barrel thickness to shoot at rifle cart velocities right? well why not make 12 gauge rifle barrel inserts to make say a 12GFH/500, 12GFH/470, 12GFH/458 and 12GFH/400???

Inquiring minds want to know...

If that cannot be done those carts will still be interesting in a single shot. Maybe add 12GFH/600 and 12GFH/577 to the mix.

boomer,
Rob's beer kegs do not fit my mould.
Rob's design was merely inspired by the beer keg shape of my Triple Foster Darwin lead slug, but his is significantly different, with five "driving rings" instead of my four, and his is a trifle shorter in length than my 1.375"-long slug.

Inserts of smaller than .729 rifling?
Monobloc of a 10 gauge shotgun into a 12-gauge rifled DR is a more interesting idea.

Riperoonie....
It is a cool idea though to have a lead/aluminium non deforming darwin...
some day having a matching mould to the Rob design or vise versa is a neet option. drop in a hollowed out aluminium darwin into the mould then pour in plain lead for a 700 to 1000 inexpensive but great grain non deforming solid. Lots of fun options to be had with the 12 GFH

boomeroonie,
No need for a mould to do what you want.
Gotta hollow out Rob's aluminum slug to do it anyway.
Just pour it full of molten lead and let it cool.
Then watch the Aluminum shatter on impact and release a 300-grain .375-cal cast lead slug to tumble onward? Splat!
Nah.
Get Rob to drill it precisely and insert some tungsten carbide.
Was that discussed on a previous page of this thread from hell, or was it on the "dart thread?"

I probably can make a Lathe Turned mold out of Aluminum to exactly the Darwin dimensions if one of you guys wants one.. Pretty straightforeward internal boring and grooving and nothing overly complex. I've thought about that as a later stage option. I routinely drill the Aluminum Darwins to 250Gr weight. The .5 inch hole is about .75 deep. Very explosive as is at 3000 fps. RIP is correct in that they shatter on impact! Usually fragmenting up to the solid Aluminum section. Very accurate so far also. -Rob

quote:

Originally posted by Robgunbuilder:
I probably can make a Lathe Turned mold out of Aluminum to exactly the Darwin dimensions if one of you guys wants one.. Pretty straightforeward internal boring and grooving and nothing overly complex. I've thought about that as a later stage option. I routinely drill the Aluminum Darwins to 250Gr weight. The .5 inch hole is about .75 deep. Very explosive as is at 3000 fps. RIP is correct in that they shatter on impact! Usually fragmenting up to the solid Aluminum section. Very accurate so far also. -Rob

Rip/Rob... gotta see what those exploding aluminium darwins @ 3000 fps do to a deer or prarie dogs ect.

Here is a bit-closer-up view of the Nohbozo Darwins,
the brass, copper and allyoominneeyum slugs are neat:





Rob,
The twisters and hail around here put a weather kink in my weekend shooting.
So has TAX TIME!

I have enough brass slugs to go on up 3-shots at a time, 10-grain powder charge increments in H50BMG:
180, 190, 200, 210, 220, 230, 240 grains

Then maybe stop at 220 grains with my Lead Darwins.

Will do ... as long as the NEF-er doth not protest too much!

Your copper slugs are beauties.
FN solid one way and cup point the other way.
Can they be driven fast enough to expand the cup point on an elephant body shot?
An Elephant Safari From Hell shall be required.

Besides the Quadracone load,
I was thinking of loading two of the 571-grain balls as a stack.
Push them through a .730" sizer by their sprue-flat and stack them with the sprue-flats down to keep them oriented.
That would be 1142 grains of 30:1, and might serve as a surrogate for 1149-grain copper Darwin load development.
Maybe 3 "lube cookies" under, between and top of the balls.
Two-ball load: A load with balls.
That has a masculine quality to it.

The balls are made using the Lyman mould for "Brown Bess" 75-cal muskets, .735" diameter as cast in pure lead.

I'll have to review the thread from hell for the proper powder and charge to use with the aluminum Darwins to get Boomers 3000 fps ... and find a rock to shoot it at, for the fireworks. Nocturnal fireballs would be fun.

How about a tri band design that is stackable in any metal lead, aluminium or brass that interlock and stack for either a one, a two or a three hole punch. brass ones should be about 400 grains

maybe say .45" from tip to bottom of interlocking rear hole and .45" from base to front of driving band. stack 3 in a variety of metals for a diff point of impact. Lightest in the rear, heaviest in the front. aluminium, brass then lead. 1.5" from tip of top 3 hole punch bullet to base of rear 3rd bullet. maybe crimp on the rear of the top bullet for max capacity.

Could be fun.

I used spacers rather than stacking cones as I was concerned the metal would swage together and not separate. The PVC spacers work great. You will get dispersion with three different weight quadracones made of different metals.-Rob

The above design was to get maximum bullet in the minimal area. maybe a paper spacer to prevent "Swaging"

I would be curious to see the poi spread of a lead, copper, brass stack.

Boomie- way too much work making Quadracones from dissimilar metals. The offset hole serve perfectly to cause off axis dispersion.-Rob

At least this one's slightly different.

3/16" x .80" side vent slots, 3/16" and 1/4" top vent holes, 3 sq in vent area. I fired one 750 gr, 80 gr 4759, 3" Rem case, ~1500fs, 8.65 lb shooter...the brake helped some...don't know how much...I like this one visually better than all the rest. Forend on order...throater for my 45-90 on order...weather still pissy...could be worse...

Enjoy your toys.

quote:

At least this one's slightly different.

Looks Great!!!

Mid-Century Modern ...

Foobar-I like this one the best so far! Your still operating in a Gas pressure range where a Brake provides minimal results. Try those 1085 darwins over 220 gr of H50BMG.-Rob

Yeah...kinda like a Cutts Comp...this one took 4 hours for the milling/drilling alone with my table top and 3/16" is about as small as I can go without snapping endmills...

Let me get all the pieces and parts together in one piece and fatten 'um up a bit before I go gett'n' all bully with the bigg'uns.

My 45-100 has the same problem with RR's 720 T-Rex slugs...NEEDS MORE FAT...

Enjoy your toys.

Looking good Foobar. I'd be keen to see how it goes with a full load. The only thing I can see that may need to be addressed is that the actual port sectional depth is rather shallow. To get a good directed blast of gas, the ports themselves need to have a reasonable sectional depth to direct the gas. Therefore, same design, just give it a thicker/bigger OD on the brake's outer dimensions should give you the sectional depth. But I like it, I think your very very close.

I've been trolling the net reading everything I can find on MB design...eveyone has a contribution to make.

I made this one thin walled partly because my table top mill doesn't have enough feel through the cranks too keep from breaking anything smaller than about 3/16" as far as milling is concerned and I wanted the least amount of material to cut through, but I can drill down to 1/16" without a problem.

I broke all my 2 and 4 flute 1/8" endmills on the mockups tring to find the right speed and cut depth...HSS, Cobalt and Carbide.

I bored out the inside of this version to almost minimum thread ID and the end hole 0.040" over bore dia...as one said having a "tunnel" slightly larger that bore dia could cause accuracy problems because of the tunnel acting like a loose bore and the gas blowing the bullet bullet around...one said that leaving baffles with a bore hole 0.020" to 0.040" would cause the gas to be deflected ouside better as the bullet passed through each bore baffle...one said two large holes on either side was the most efficient, dumped the gas the quickest and provided the highest level of recoil reduction...like my "Panzerschnozle"...that one should make the gas jet recoil level "0" and efficiency 100%.

The Vias brake is about 92% efficient and this brake is about 86% efficient, but as far as the difference in recoil reduction is concerned, it is very low, on the order of 34 ft lbs for the Vias and 35 ft lbs for my design using the same load - 750 gr bullet, 1600fs and 80 gr powder, 14 lb rifle...against 56 ft lbs without the brake.

Lots of good ideas that sounded reasonable but I would need a CNC machine that could turn out a brake in a very short time and a bunch of sophisticated measuring equipment to really do the job.

When it gets warmer I'm gonna skin down, grab a water hose, stick it in the big end and turn on the water...just to see what the pattern is.

I'm getting antsy to get some loads worked up but the weather isn't cooperating...cold, wet, windy...can't setup my chrono...

I wanna go play...

Just found out my favorite gunshop is selling out and he can't find anyone to take it over...bummer...no place else in town to find good used guns at a reasonable price. Sh** is really happening all over.

At least I got the 45-120 reamer ordered... think I can get Ranger Ricks 720 gr T-Rex slugs up to 2 large????....whoooeeee...talk about some whackadoo


Enjoy your toys...

So what do you guys think about a HOWDAH from HELL! Pistol Gripped NEF with a 16 inch barrel. Think we can find someone to shoot it?-Rob

quote:

Originally posted by Robgunbuilder:
So what do you guys think about a HOWDAH from HELL! Pistol Gripped NEF with a 16 inch barrel. Think we can find someone to shoot it?-Rob

Rob,
Gotta be a double to be a howdah.
Duct-tape two of them together and you might get shootaway to try it. He will certainly need his shooting helmet for that one, as well as a face plate, mouthpiece, neck brace, chest protector, and some gloves and wrist braces. That would be worthy of his videotaping enterprises.
The blood will show up nicely in the snow.

Rob... just use the excess barrel lengths of your 12 bore to be double for a real double barrel Howdah from hell.

RIP- You really think Shootaway is that stupid? Wait I KNOW THE ANSWER! Now there is a video I'd pay money to see. He could wear a hockey mask for a friday the 13th shooting video! It would contrast elegantly with his helmet! Do you think we could get him to do it? I really likethis idea.!-Rob

quote:

Originally posted by boom stick:
Rob... just use the excess barrel lengths of your 12 bore to be double for a real double barrel Howdah from hell.

I'll be impressed when one of you whackos builds a 12GAFH six shot revolver carbine and a couple speed loaders to go with it ...

Rip:
Matey, I cant recall the maximum amount of powder that you have successfully loaded into a 3.5" RMC casing to date (any load). Can you pls refresh my memory, thanks.