500 Jeffery based wildcats

[Swamplord]

For those of you that asked for info on my wildcats based on the big Jeff case, here ya go...

I developed the dimensions for the .375-500 Jeffery in 2004 but it went nowhere, the gunsmith I was working with at the time refused to build me a rifle based on my design, I had a tendency to like faster cartridges and he was one of those old bastards that believed the .375 H&H is all you need... and I simply refused to have a .375 H&H ( as a teen I was almost shot in the back of the head by my hunting partner with one) I hated the **** thing ever since .

anyway... with the popularity of "The Pigman" on tv and his developement of the ".338 Twisted Pig" cartidge with Twisted Barrels, my interest in my design was renewed, 500 Jeffery brass is made by Jamison, Norma and Bertram.. yes, it's very expensive and hard to find in stock at this time, but it is available !!!

I have contacted Dave Kiff at PT&G to make me the reamer, after altering some of my dimensions to maximize case capacity and create a .338 cal. version also, the reamers have been ordered !!

Thus... the ".375 MJOLNIR" The Hammer Of Thor is finally going to be built..!!!
(pronounced Myolner and is the Hammer of the Norse God of Thunder "Thor")

it has a .357" long neck, 35 degree shoulder and case water capacity is 147.6 gr. ( according to Quick Design) approx. 24 gr. more than the .378 WBY, and 38 gr. more than the .375 RUM.... and a whopping 58 gr. more than the .375 H&H....

this will be built on a cm Rem700LA with Seekins 3.9" detach. mags as a repeater for regular hunting bullets, for long range it will run the 350 gr SMK's and 330 gr. and heavier Cutting Edge bullets as a single shot...

the .338 is similar in design ....350" long neck, 35 degree shoulder and case water capacity is 145.1 gr....

Velocity is just Quick Load estimates at this time, the cartridge should place somewhere in between the .378 WBY and the .375 Snipe Tac...

and that is just a guess at this time,

the Pigman claims 120 grs. of powder gives 3400 fps with a 250 gr Hornady in his
.338 Twisted Pig and with room for improvement, I can see 3500-3550 easy with coated bullets !

 

[Frank in the Laurels]

I wouldn't want to be on either end of this rifle...WOW!!!!

 

[laserflat]

Awesome. Yessir this should be a hammer for sure. Im really anxious to see the .338 version as it should just fall just below the .338 Allen Mag. Please keep posted. Both should make nice 1250+ yard Elk rifles. Ive always been interested in a .500 Jeff-based wildcat. Not much smaller than the Gibbs but can be run at higher pressure. Not sure on credibility, but Ive read that because it is a higher pressure cartridge it always outran the .505 in factory and handloads...

Any idea when the first rifle will be done?

 

[Swamplord]

Recoil can be tamed with outstanding brakes like the Muscle Brake or the Painkiller......

Rifle is being built as we speak, waiting on the reamer and case forming dies to be made.....

the .338 cal. version will be added at the same time as a second barrel for the rifle, here are some specs on the cartridge............

.350" long neck, 35 degree shoulder and case water cap. is 145.1 gr. (Quick Design estimate)
attached pic has more case dimension #'s

approx. 18 gr. more than the .338 Excalibur
23 gr. more than the .338-378 WBY
27 gr. more than the 8.59 Lazzeroni Titan
33 gr. more than the .338 Lapua Mag
37 gr. more than the .338 Edge
40 gr. more than the .338 Norma Mag and .338 RUM
62 gr. more then the .338 Winchester Mag
(these are ammoguide water capacity estimates)

all these estimates may vary + or - a grain or two, just a ball park comparison to give you an idea of case capacity.......

If a 338 Win Mag is a hard recoiling cartridge for some shooters... this is not the cartridge for them , as this one has almost twice the capacity !

Haven't named it yet so it's still the .338-500 Jeffery at this point . reamer has been order per these dimensions...



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[MontanaRifleman]

Sweet! Both of those look real interesting! Might have to do one or both some day.

Is a 700 action going to be OK for the 500 Jeff?

 

[FEENIX]

I wouldn't want to be on either end of this rifle...WOW!!!!

I agree! Awesome wildcat and awesome name. Good luck, thanks for sharing, and please keep us posted.

Ed

 

[Varminator 911]

Some question a Lapua on a 700 action. This is fatter yet. Is that enough steel?

 

[Swamplord]

Some question a Lapua on a 700 action. This is fatter yet. Is that enough steel?

Enough steel where ? don't know what you mean ! give me a valid question so I can answer it !

many 338 Lapuas have been built on the Rem700 actions and including 7.82 Warbirds, both operate at higher pressures than the 500 Jeffery

Rem 700's can be easily made to run the parent 500 Jeffery cartridge, don't see why necking it down to 375 cal. would make a difference !


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[Swamplord]

I necked down the 500 Jeffery case to get an idea on what it would look like, the neck will be longer of course, I left it short so I can measure the chamber first to make an adjustment to fireform with proper headspace..... the shoulder will also be fire formed up to 35 degrees...

necking down wasn't as difficult as it would appear to be, I had most of the necessary dies to gradually reduce the diameter of the neck, after determining the proper diameter I bought a couple more die sets to get the proper squeeze....
I just used the bottom portion of standard caliber dies with the appropriate diameters to reduce the neck with zero case losses.... (lotsa Imperial wax)


500 Jeffery .532" neck OD

500 S&W .530"
300 Win Mag .513"
6.5x284 .500"
6.5x55 Swede .480"
454 Casull .477"
30-06 Springfield .470"
44 Magnum .457"
220 Swift .445"
6.5 Grendel .437"
40 S&W .424"
30-30 Win .419"
25-35 Win .416"
5.45x39 .394" final die used and 330 gr. Cutting Edge bullet seated with good tension

I realize that is a lot of steps and a lot of dies.. but it worked and I gradually reduced the huge neck opening down to accept a .375" bullet with no problems, I have a batch of brass ready to fire form and did not need to purchase expensive case forming dies ( $500 and 6 month wait was the quote )

Now I have $500 saved to build a real set of dies from my fired cases !!!

Next I will work on continuing to reduce the neck to accept a .338 cal bullet...

additional dies required

9mm Luger .391"
9x18 Makarov .384"
357 Magnum .379"
30 Carbine .354" ready to seat 338" bullet

gotta get me the 30 Carbine and 9x18 Mak dies and ready to go !


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[tim jurczak]

I am always amazed when guys are excited to shoot cartridges of this magnitude. The muzzle breaks used must be quite effective??? I own break less 8MM Mag and 340 WBY and consider those quite substantial as far as recoil is concerned. Holy crow! Good luck with this. I was hoping to see more happen with the 6.5 Prometheus as well.


Tim J

 

[MudRunner2005]

Swamplord.....What program are you using to design those cartridges? I have been looking for a cartridge building program that actuall works (RCBS Load v3 doesn't work unless you're a computer nerd).

Anyone know of a program where you can design a cartridge, simply by inputting different dimensions and it automatically changes its look, as you inpt different data?

I have a cartridge design in my head, but have no way to design it other than drawing it by hand, which is difficult. I'd rather have a 3D model on a computer with all technical data.

 

[Swamplord]

The 6.5 Prometheus project is alive and well, have the rifle completed, waiting for Neil Jones to finish up my dies and will start load development when dies arrive, have a fluted 8.5 twist BRUX barrel to burn up with load developement and fireforming brass and to see how long the tube will last, then will throw an 8 twist Bartlein bbl on. I'm hoping throat life will be a bit better with the long neck and 35 degree shoulder, we shall see.....


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[Swamplord]

Swamplord.....What program are you using to design those cartridges? I have been looking for a cartridge building program that actuall works (RCBS Load v3 doesn't work unless you're a computer nerd).

Anyone know of a program where you can design a cartridge, simply by inputting different dimensions and it automatically changes its look, as you inpt different data?

I have a cartridge design in my head, but have no way to design it other than drawing it by hand, which is difficult. I'd rather have a 3D model on a computer with all technical data.

I use Quick Design, I just pull up the parent case I am working with then tweak it with the dimensions I have in mind. It does exactly what you describe and works with Quickload its sister program..

If you want, pm me to get my email so you can send me your info and I can draw up your cartridge and compute all data as case water capacity and shoulder angle...etc..

 

[Swamplord]

I have successfully completed necking down the 500 Jeffery case down to .338"

using all the steps as for the 375 then continuing with the next steps

9mm Luger .391"
(did not have 9x18 Makarov dies at .384")
357 Magnum .379"

the final die body used was the 357 Magnum and did not need to use the 30 Carbine die,
338 cal bullet seated with good tension for fireforming

Once the first case was successfully completed I came up with a name for my new wildcat...

"338 WOLVERINE" (The Alaskan Beast)

in the pic below the case is almost ready for fire forming, neck left short intentionally until I have a chamber to measure then the neck will be lengthened and shoulder fireformed up to 35 degrees...



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