John Ricks was talking awhile back about the Gibbs case - more specifically the Chey-Tac case - and its utility as the parent for a DG cartridge.
Well, it so happens, trim the Gibbs down 1/4" and it has almost the exact lateral dimensions of the A-Square (but with 18% more water!)
[Someone was mentioning they had a 505 on a 416 Rigby Ruger, and to feed they had to trim cases down 3/16 or so; no problems firing.]
Neck it to .51" for a "proper" 50-cal, and seat it to 3.75" or so, and this case will hold about 123.5g of powder behind Woodleigh's 600g PPSN. [Incidentally, Nick Caico's loads (see AR Reloading pages) never exceeded 120g.]
Do the same thing for .475" to "fix" the 470 Royal, and get Mbogo performance without those insane 53k psi pressures!
The point is to make the Gibbs available to a wider selection of actions. (And to use some of the most expensive brass there is!)
Chamber it in a CZ, shouldn't be too hard to get 3 down, and you'll get all the fun you can stand.

408 Chey Tac case is a derivation of the 505 Gibbs, but with a much stronger head and web design.

Been thinking about contacting Jamison in Sturgis (the case maker) to find out if he would release cases with no headstamp and not necked down. Would be an excellent case for the big'uns.

I have a few 750 grain soft nose .510 bullets on the shelf. Hmm.

I was reading somewhere that MAST was helping with those cases, and I see they carry the Gibbs.
Wonder if it's with the new web, or just reglah' style.
Anyway, seems like Dr Taylor would love to see it wildcatted. Why not sell Basic?
John, what are your druthers? A straight 510-408 CheyTac? Or some changes otherwise.
I have wondered what the 470-505 is like. Royal Arms made at least some.

I am kind of confused... maybe the two of you can explain in closer detail.
Why bother with the 505 gibbs case at all when you have the 460-500 (510wells 500a-2) you can get 2400 even 2500 with 600 grain projectiles. All the actions that are "big enough" (read wide enough) are also long enough for the 510/460s, so shortening the gibbs buys you what?

Gibbs case has more volumn which equals less pressures for same velocity.

My thought is to run the Gibbs case full length.

Or shorten it a bit, you will still have more volumn than a 460/510 case.

[ 11-15-2003, 08:11: Message edited by: John Ricks ]

John... I figured thats what you were getting at. I have always been a priss about the fact that the 505 was .505 and not 510, always chapped my hide. This year I will be putting togeather a 510wells or 500a-2. It will be on a cz550, any suggestions. I would like to put it in a accubond lam. have a master piece front, and a quarter rib done up on a friends Hass CNC after I take closer measurements, pac-nor barrel. Id like to pillar bed. I will be doing the rust blue and the sights. Any suggestions?
also .... on the acrabond I would like a abbreviated forend, that is slender, like some old rigbys.

There just don't seem to be any actions to fit that monster without spending a ton of money.
The CZ is such an accessible action it makes sense to me to bring it into the 3 1/4" range.
You'd still have a lot more room than the Weatherby case.
Can the Rem Model 30 handle a Gibbs?

To me, the 408 CT seems a bit overbore in a hunting rifle (a carrying hunting rifle, I should say.) You can get more speed than most care for out of the Rigby case, and if you had to, it could be blown out even. But 47 cal or above, and I'd be game. (Er, I mean, I'd use it on game.)
I tried to draw up a .585" number, but it just doesn't quite fit. I do think a .550" is doable, now that AR is starting a bore size de novo -or whatever that term is. Once the 550 Mag gets off the ground, maybe some one will try it on the CT case.
I love the idea, myself.

It would be interesting to design a cartridge to fit some BMG VLD's into a 4" action and see what they'd do. Sort of a short-action BMG....
The 50 Whisper, of sorts.

first run of 408 was made in Germany by a small company , I have never see any Jamison case brand in 408 , only I own and use are german made and quality are very good

I have nothing again Jamison but check quality before , because 408 case are a bit more costly than 308 WIN surplus once fired case

good shooting

DAN TEC

Dantec, tell me about your rifle. Is this a tactical sort of thing, a long-range hunter, or what? Bbl length? What sort of loads do you run and with what bullets?
By German do you mean Dieter? I'm sure he would make a run of unstamped 404 Basic, probably a 300pc, two-year minimum or so!

I have designed a cartidge based on a 505 Gibbs I call the 500 Dark Continent. I worked with JGS to get the reamer specs ironed out. The cartridge has a standard body taper and 25 degree shoulder for good feeding, is 3.85" in length, .510" neck, and shoots a .510 caliber bullet. I like the .060, no-rebated rim of the Gibbs case much better than the .040 rim of the Jeffery or the 500A2. I wanted a cartridge design that would statistically feed better than anything we currently have at the .510 caliber. Also, I will load it to 45 to 50,000PSI to yield 2350fps with a 600 grain bullet. I don't think anything more is needed for any game animal. Of course, if a loading will work with no pressure signs in Austin, TX in August, it would probably be alright on the surface of the sun!

I will be ordering the reamer soon but will take it slow on the build. I'm saving for my first trip to Africa right now.

-Catter

catter,
I'll be a crash test dummy for ya!!

jeffe

Wildcatter, that sounds just great.
In what will you be chambering that monster?

An Ultra Mag from Olympic Arms or what ever, CZ, Bauska, BRNO action comes along. In want to build a classic express type rifle with fine walnut and a 1/4 rib. Mercury recoil absorbers in the stock, weight of 11 lbs. Mabye some porting if I find I can't handle the recoil after the first 100 rounds of test fodder. That is still over 100 ft/lbs of recoil.

I don't know exactly what the powder capacity of a .505 Gibbs case is after you trim it back 1/4", but I would guess it might be a little bitty bit more than 123.5 grains, though it depends on the powder....

With a full-length case and 3/4" of .510" 700 gr. SBT in the neck, I kept pouring in the WC 872 one grain at a time, but the velocity just wasn't going up much. I got frustrated and switched powders, but my guess was I was going to get 160 gr. or so under the bullet if I had persisted. Those balls pack pretty dense.

My second try was with IMR 5010 and I kept going until no more would fit, a compressed load of 145 gr, for (pop!) 2075 fps. Those Lincoln logs don't pack tight if you just pour them in and tap the case every now and then. Might do better with a drop tube.

My third try was with WC 852 (slow). 135 gr duplicates .500 A-Square, and it looks to me as though it might go to 160 gr. too, though you would likely reach the safe maximum before that. I might finish restocking in May-June, and then I will add a little more powder.

Some shooters consider some bolts to be marginal for the .505 Gibbs rim diameter. The MRC's .8" bolt and 4" magazine (right?) in the large action are going to be a good match for the rim diameter and COAL of loaded .505 Gibbs rounds. The wildcatters will get a new lease on life, but it will be a little more expensive for them than those soda-straw calibers they are used to working with...