I am working on a 408 Cheyenne long range rifle. Most know this is a .408 bullet on a completely redesigned 505 Gibbs case that has greater web thickness, greater side wall thickness, and better alloy than the old 505 Gibbs cases. And, the cases are more dimensionally constant. These things are real strong, the Chey Tac crowd is running them at 70,000 psi in quality custom actions that are breeched with minimual clearances and obtaining more than 10 firings on a case. Advanced production is being set up now for increased numbers of cases manufactured, this will bring the cost down to reasonable levels, and as they will be US made, the opportuity exists for custom headstamped brass.

IMHO, this is an ideal case to work with for a 50 cal. DGR. Already has a correct shoulder, is very strong, just needs a neck up to take a .510 bullet. Run it at 45,000 to 50,000 psi and have all the performance your shoulder can take, plus never have to worry about sticky cases in the hot Zim valleys in the Summer.

With the upcoming Montana action at a 4.00" magazine length, and a 1.125"-16 barrel thread, the opportunity exists for a DGR that can run something like 600 or 650 grain round nose softs and the long "solids".

If my gray haired memory holds the thought, I will take a photo of the Cheyenne case and post tomorrow.

If anyone is interested in a DGR on this case, post a reply. I might draw up a reamer spec for a 470 or a 50 on this case.

John - sounds pretty scary, I may be interested in 50 caliber .510" - would this work effectively with a 24 - 25" barrel length? Got any ideas on estimated velocities with a 600 grain bullet? a 700 cast bullet ? Manageable with a muzzle brake and total weight of 10.5 - 11 pounds? Isn't this what health insurance is for ? Neat idea, good luck - KMule

Mule, this is all feasible. It would be a easy shooter with a brake, and still managable without a brake provided the velocities and chamber pressures are kept down to reduce the gas jet effect (a major portion of recoil).

I have shot a 9-1/2 pound 500 Jeffery, unbraked, the recoil is not really that bad.

I like the heavier bullets in the.510, good sectional density and penetration. The 535 grain bullet in the 50 cal's has always looked stubby to me.

John,
I just sent you some pics of the .408 alongside a 30-06, Rigby, and BMG round for size comparisonship.

BMG

How about posting those pictures here gents? - Dan

I can't post pics, but I'll send them to someone who can.

BMG

Clymer had an off-the-shelf .510-.505 Gibbs reamer. I think they called it .51 Gibbs. If you don't want to reinvent the wheel you could just use that. It could be though, that you will want changes to neck wall thickness, shoulder, taper, etc.

BMG, no need to send the photos, I have all the cartridges you listed, plus reamers for such. And my server is set to reject files over 100K to prevent scamming, so likely the photos went astray.

SDS, I do not use standard reamers, just too much variation. I design my reamers around the case actually used and the conditions & specifications of the rifle, and since mine are set up for muzzle flush coolant and removable pilot bushings, they are all special order.

Many in the past have set up a 505 gibbs for .510 bullets, but this is risky, as you still have 505 on the case headstamp, sometime in the future one of the rounds could find its way into a 505 barrel. The solution is a case sufficiently different in dimensions so it will not chamber in a 505 Gibbs chamber, plus the proper headstamp on the case.

So, what to call the beast? .510 ???????

I thought that I already posted a picture of the 408 CheyTac and 505 Gibbs a while back. Check out this link. Thanks.

http://www.serveroptions.com/ubb/ultimatebb.php?ubb=get_topic;f=16;t=003167#000004

That brass would make a long belted 55 cal
straight case about 3.12 in long.Ed.

John, how about just .500 Gibbs? People will know what it means.

Thoughts on smaller diameter bullets using fat cases; have you noticed it seems the point of diminishing returns is reached about 3,450fps? For example the 6.5x300 Winchester, same velocity as 6.5x300 Weath and 6.5x378 Weath. All at about the same pressure.

.300 Ultra, .300 Pegasus, .300 Lazz, all about the same at (reasonable) pressures. I know Lazz runs his into 65-67kpsi.

.338 A-Sq, .338 Pegasus, .338 Lazz all about 3,120fps.

I wonder if the .640 headsize but short 2.5" (base to shoulder) case length would be able to drive .338 bullets at 3,450fps in reasonable pressures?

Why not the 500 or 510 Cheyenne? OR the 500 RICKS after all it is your idea.

Roger,

The 510 Gibbs is already in existance. Dennis Olson has a reamer for it and Ch4D has dies on the shelf for this cartridge. Thanks.

Roger proposed a "what if" for a 2.5", 338-505. I ran quickload for 26" barrel, 250g hornaday, case capacity=145g, OAL=3" and got:

velocity = 3000fps for 67,000 psi.

my computer blew up with the pressure for 3400fps

steve

PS
just found this over at CH4D:

500 Gibbs 2.5" 4 J $ 161.00 43, 57, 500 - -

[ 05-23-2003, 23:59: Message edited by: steve505 ]

HERE is the link for Chey-tac

http://www.cheyennetactical.com/

I've worked with Dr Taylor and "willie" on the project and the brakes are made by a friend of mine. THEY REALLY WORK.

GREAT CARTRIDGE!!!!

John,
I also have been somewhat interested in the 408 Chey Tac. What actions will work with the 408? Could it be stuffed into a Ruger #1?

Also, where can one get a couple of sample cases? EDM? What's the availability of dies? Bullets?

Thanks in advance for your reply,
Herb D

ED how do you get a belt on there?? I like the.55 idea RNS

[ 06-10-2003, 21:38: Message edited by: RNS ]

The 408 dies are available from RCBS about $129.00

RNS--All--To put a belt on the Cheytac is just the
same as doing it on BMG brass,As long as the base
is thick enough.I havw a case spinner lathe,
made from a wood lathe.It is geared down.I have tools that I use to start belt shoulder, then I swage the rest of it and case shape.I section cases first
and determine where belt should be.That case is built heavy, so it would work great.Ed.