It's been a while now and it's certainly is good to see people continuing with oddball projects,,,.This time the .620 rimless magnum,,damn impressive.
I hope someone have some answeres.
when can we expect to see some real-world load datas on the "map", and what is this cartridges ballistically potential,,,and why the belt !!!

Per".620 rimless"

Per577,

I amy be wrong but I think the belt is needed to headspace on as there is no shoulder.

BUT a 45/70 is a straight case and it does not have a belt, does this mean the 45/70 headspaces from the rim ??

The 45/70 is a rimmed cartridge, it headspaces on the rim.

A case with the body size of the proposed 600, if it was rimmed, would be to big for the actions.

Also, the original concept of the belted case was to give the positive headspacing of a rimmed case but without the potential feeding problems of a rimmed case in a bolt action.

Mike

So Mike this 600 Ok is not a goer unless it's done without the Belt ?? My thoughts also revolve around the issue of how far do you want to push the 602/550 action. Peter Vanmueres from Pro-Cal trading would not build a .585 action on a 602 or 550 as he though it was on the actions limits. Then again some smiths will not do anything over a .500 nitro on a Ruger #1 as there is not enough metal left.

The .600 OK has no shoulder, so the belt is necessary for headspacing.

If it were designed to have a shoulder, then the case body would have to be substantially larger, resulting in a SEVERELY rebated rim, giving rise to nightmarish feeding problems.

The belted case is the best compromise.

PC,

You already know that Peter Van Meurs is full of bullshit.

In my opinion the locking lugs on the Mauser are the size they are because they look right on that bolt. The bolt size is purely a product of a .47 case head size and a 2.3" or so case length.

Would I fire a 600 OK on a CZ with steel cases. Yes. Would I continue to fire it. Yes

Will a Model 70 with one lug bearing take up pressure on the other lug with big pressure loads on H&H case so that both lugs bear...No....In other words one lug will still be bearing.

But, if you believe what read/hear, then then the Mark V Wby is there.

Mike

Per577...!

Hi Per, you have been away for a long time. The name of the .600 Rimless Magnum is .600 Overkill It is Robgunbuilder that got the idea. Caliber .620 with a 900 grain bullet at 2500-2600 fps... That will be some thing for us in the future.

Have Ulrik done any shooting with his .577 TYRANNOSAUR...???

Yoo,,Overkill !!
Yes,,Ulrik's being shooting some in africa these days, and he's back in Norway,,i called him the other day, and he had shot two buffalos with his .577 T-rex and an elephant. He used an almost full power load going 2650 fps !!The bullet exited lenghtwise,from the butt and all the way through it's internal organs,i'm not sure. But the elephant went only 5 yards before collapsing ! Impressive. Think you'll be jealous when i tell you that i'm going to try his .577 T-rex, unless he decides to do something else. It's just maybe, but i can't wait to try the bastard,, and experience what power this thing will develop,,i'm a sick guy,,but hey,,at least i will, then get to know what i'm into,,thinking of geting one myself,,.585 NYATI IMPROVED or .577 T-rex,,,or the new .620 Rimless,,or OK,,OKEY !!!!!
HOPE FOR THE BEST ,,EXPECT THE WORST !

Just a little correction Per,

I shot a zebra, a buffalo and an elephant in Zimbabwe, Matetsi unit 2.
The buff and the elephant was both taken with a single heartshot with the .577 Tyrannosaur and yes the elephant only went 4-5 yards...
The lengthwise shots were taken after the elephant was dead and they entered through the chest and went into the intestines - almost lenthwise through him, but they did not exit.
The tusks were 184 cm / 60 pounds and 196 cm / 66 pounds. A nice elephant indeed...

Imagine it as a scaled up 458 lott. The belt is needed for the same reason, to provide headspace on a case that isn't large enough in dia to provide a sufficient shoulder.

The thought is to maximize what can be utilized through the relatively inexspensive CZ 550 actions. Physically, only so large of a rim and so large of a case can be used on these actions. In a rimless, beltless case, the 585 Nyati is max, in a belted re-bated case, the 600 rimless is it. Rob also wanted to use an existing case, so I took the 585 case, and added a belt to it. Ok, this isn't really an existing case, but it will be easier for the custom brass producers to make then something totally from scratch. There is also a desire to use a case that isn't too big, as there is only so much powder that can be effectively lit off with magnum berdan primers.

I'm not sure how long it will take before barrels are produced, I'd think the first rifle will be done somewhere around the end of the year. I'm not sure about dies and brass. I believe the goal is 900 gr @ 2400 fps

I think I'll just have to order one of the barrels

Paul,

Is the .620 Overkill going to use BOXER or BERDAN primers?

In my mind, I was thinking Boxer, I know I was, but somehow, the fingers came out Berdan. I believe the problem was, I was too focused on mixing them up, and so I did

Hey Overkill,
I just wanted to congratulate you for have a cartridge named after you!
Good Hunting,

Per577...! So you are going to try the .577 Tyrannosaur. With full power loads I hope. You have to tell me how it was then.

Ulric Hentzer...!

A singel heart shoot and the elephant only went 4-5 yards I love the .577 Tyrannosaur

Do you used the 750 grain Woodleigh soft point on the zebra..?? how was the wound channel and the effect and expansion??????

Overkill !
Well as i posted, i speaked with Ulrik and it was just a maybe,,but if the issue comes up,,and if it is talk about when,,,and not if this incident will happen at all,,,i certainly will be happy,and terrified at the same time !!!
And if the things work out fine, i hope to try a load at 2600+ fps,maybe 2660 fps !That's way over 11.000 fpe !(sorry the language)

Per"577 T-rex"

Per577 look at this...!

The .577 Tyrannosaur ( 750 grain bullet at 2650 fps) will have a recoil energy of 202 ft.ibs if the rifle weight is 13 pounds.

The .620 OVERKILL but okey the .600 Rimless ( a 900 grain bullet at 2600 fps) will have a energy of 244 ft.ibs if the rifle weight is 13 pounds. If the weight is 16 pounds then the recoil is 198 ft.ibs

And think about the .700 BMG IMPROVED ( 1000 grain bullet at 3000 fps) or (1200 grain Hawk SP special order bullet at 2500-2600 fps) The recoil energy of this gun will be 221 ft.ibs if the rifle weight is 25 pounds. If the weight was 16 pounds then the recoil would be 346 ft.ibs

So I think that these rifles should have a VERY good muzzle brake. But would a good brake take away so much of the recoil. I know the feeling when I shoot my .460 Wby with muzzle brake.

I have been asking black-powder-big-bore about his 2-Bore and he says that it shoot a 3550 grain round ball at 1350 fps. That give 14 370 ft.ibs of kinetic energy. But a .700 BMG IMPROVED will give a energy of 18 000 ft.ibs with a 1200 grain bullet at 2600 fps. The 2-bore have a bullet diameter of .1300 But if a 1200 grain bullet in caliber .700 expand to the double orginal diameter then it make a bigger hole in game. A expanded diameter at over .1400

But I dont know wich of these calibers will have the best "stopping power"??? what do you think.

The .620 Overkill would be a fine cartridge in the future because it is possible to make it on a BRNO CZ 550 action. But a .700 BMG IMPROVED would be even more fun.

Ulrik...!

Do you have any muzzle brake on your A-SQUARE HANNIBAL .577 TYRANNOSAUR rifle...? And how big hole was it in the zebra that you shoot with your .577 T-rex???

Overkill !
No I do not have a muzzlebrake on my 577 - and I don�t want one either. The recoil is not a problem from field shooting positions if you are properly build.... ( one of my wimpy friends just teared off two ribs completely (which he broke almost one year ago) when he tried the rifle recently.....
The wound channel in the elephant shot with a 750 Woodleigh FMJ was huge - the hole in the heart was a bit over 10" in diameter...
The buff I shot with a Dead Tough softpoint (A-Square)through the last right rib. The bullet expanded perfectly and went diagonally through him ( a quartering shot) and was found under the skin on the opposite side in the neck/shoulder junction.
The zebra I shot with a 416 WBY and Barnes X bullets.