Despite my unfortunate dalliance with the PATHETIC case of AXEL/TROLL/DEMPLE- I have had a discussion with PAC-NOR about the barrels for the .600 OVERKILL. I have asked them to give me final quotes on the .600 OVERKILL barrels in the following configuration.
1. 28 inches long stainless steel and Chrome Moly
2. 3- groove 1:20 twist. The three groove barrel is non standard and it adds $250 to the total cost as a new button will have to be made. If 10 of us go in on it, it adds only another $25 to the cost.
3. Pre-Fit (Long Chambered), threaded for the CZ550 to my .600 Overkill Reamer dimensions. ( I will make these dimensions available and thanks to Fritz454 for the CAD drawings.
4. Optional threading for a Muzzel Brake, I suggest a 7/8 or 1 inch X 24 TPI ( Brake from VIAS or Bear CLaw perhaps, I will also make brakes for folks if so desired.)
5. #8 Contour - 1 inch at the Muzzel
6. Pac-Nor will also crown the barrels
7. I will have headspace guages available or you can order your own from Pacific Tool.

Pac- Nor will give a 10% discount on ordering 5-10 barrels and 15% on 10-15 barrels but they will have to go through a single account. I am willing to broker this for those who want in on the project and will manage it just like I did on the 585 NYATI project. Thus, I will need a firm commitment and a check by let's say the middle of October.
I'll post the quote later today.

Very facinating Robgunbuilder !
Keep on the good work,and thank you for your info !

Excellent. I am still in.

I have a question about twist. The 600 nitro at 1950 fps uses a 20 twist. Since we are trying to go to 2400 fps, shouldn't we have a faster twist? I was thinking 1:16 or so.

Also, I think I want to build mine on an Olympic Arms action. Do you think it will be a problem for Pac-Nor to not thread one of the barrels?

Or am I making a mistake by not using the CZ550?

Please comment.

[ 09-26-2002, 00:52: Message edited by: 500grains ]

Forgive my ignorance, I come to learn only. What is the advantage of the three groove barrel over the more conventional 4 groove? I mean there is an advantage isn'there? It cost more money after all.

Much appreciated,
Axel

Axel,

In theory ... fewer grooves create less friction, resulting in greater velocity.

In reality ... the lack of repeatable and consistent significant improvement, brings the "law of diminishing returns" into major play. Cost of producing a far less popular variation is what established the 4 groove standard (in this application at least) in the first place.

It's kind of "playing for the sake of playing" here.

But what do I know...??

jeffeoso,

I have not ordered an Ultramag action for this project yet. I purchased an Ultramag action new but second hand before. They are rough (very) but I like the idea of a .720 bolt diameter when dealing with a .640 rim diameter.

I think the Ultramag action retails for $600, and so does the CZ.

Folks- I just received the quote from Pac-Nor. It looks like a base price of $261 for stainless steel, and $216 for Chrome-Moly, number 8 contour 28 inches long. Pre-Fit ( threading,chambering and crowning is an additional $75. Threading for a muzzel brake is $75. We will also have to add an additional $25 each for the three groove button.
Thus, for example, assuming we get 10 orders, a three groove SS barrel, pre-fit to the CZ550 and threaded and crowned for a brake will cost $436.
If we want CM barrels ( I don't care myself) it's $391.
Threading for the brake is optional. Thus, the low cost approach would be CM(pre-fit) 3-groove
for $316 with no brake threads.
The barrel prices include a 10% discount assuming we order 5-10 barrels. It also looks like they will all have to be CM or SS.
I believe the three grove barrels will provide additional velocity at potentially lower pressures. I have had excellent reports on the use of three groove barrels and on this project it makes good sense. The cost of a $250 button split over 10 of us is trivial, but a barrier for an individual. I'd like to give it a try.
I can also talk to george Vias and see if he will give us a discount on his new brake. I've used them on other really big bores and they work exceedingly well.
500 grains- I also like the Olympic Arms action and it would work just as well I believe as the CZ. However, Ed Plumer at AHR is working with me on the prototype and Ed's folks are pretty good based on their knowledge of this action and their experience with the 585 AHR( I want to get three down in the box). Ed's also helping to get some brass made as we will need it. I doubt that Pac-Nor will want to do a one of. For that reason only, I'd go CZ550.
Pac-Nor want's a 50% deposit so we will have to make a decision fast. I'd like to order on Oct 15th. personally, I've had really good results with a 1:20 twist with 900 gr bullets at 2500fps so I'd reccomend not changing that.

Axel-If you want to play nice your welcome here, if not, I'm really not in the mood!-Rob

[ 09-26-2002, 05:04: Message edited by: Robgunbuilder ]

500grains,
If the velocity is going up, then a slower twist (1 in 20") barrel such as RGB is suggesting would be called for rather than a faster one.

We wouldn't want to encounter that hobgobblin "overstabilization" now would we.

If you are thinking of using 1500 grain bullets or long and pointy monometal bullets, then the faster twist would make sense, but you knew that, you just been discombobbulated.

Now I understand. It is believed that the extra money will provide a few extra fps. Interesting.

Thanks,
Axel

Rob,

I would prefer a CM barrel over stainless but whatever the majority wants I'll go for.
# 8 contour
28"
pre-fit for a CZ 550
3 groove rifling
Thread for a Vias break

All looks good. Where do I send the check?

John

Folks- Remember this thing is aimed at a max load of a 900 gr bullet at 2400fps. I don't want it to go faster. I'd like it to do it at lower pressures if at all possible. In this weight of gun the recoil will be so ferocious anyway that most of us will be happy with 600 NE performance. -Rob

jeffe,

I have just ordered a UltraMag BBK-01 a couple of days ago. My good local dealer told me that it will be around $515 and it will take 4 weeks to get it. This is about $100 cheaper than my 416 Rigby CZ 550 complete rifle. I think the roughness can be polished out nicely so I am not too worry about it. I like the .720 in diameter bolt and the Winchester safety system. I plan to have my rust blued and mate it with a polished stainless barrel. I will try to post some pictures when I get it. Later.

Cheers!
Ming

Do you tell me you've already tried the damn thing, from a remote- controll i guess !!
I just needed to have my stupid hypothese confirmed,,that you actually hit 2500 fps with that 900 grainer ??
And could you compare the costs for both the .620 RGB Improved on the full scale .50 BMG,,,aaaand the .620 Overkill ?Thanks

OK, I'm in with the CZ550 route, deep chambered (Thanks!) and threaded for a Vais brake.

Is it better for Pac-Nor to thread for the brake instead of having Vais thread it?

Also, do you know if Vais can make thre brake barrel diameter rather than having it stick out like a big shower head at the end of the barrel?

Can Vais make a threaded cap so that we can take the brake off?

All of these questions obviously make me the typical ugly American consumer.

I think we should do a mass order on Vais and on CH4D too.

Thanks for all your hard work Rob.

Oh yeah, I will go with either SS or chrom moly. Let's let majority rule.

Have you guys considered polygon rifled barrels?
Just curious.

[ 09-27-2002, 02:10: Message edited by: Bear Claw ]

Ming,
thanks tons. As I like a heavy matte finish for a dgr, I am not overly concerned for the finish. UNLESS it's big ugly tool marks.

Thanks for the info
jeffe

Crome-Moly, threaded,chambered and crowned. 3-groove or regular (whatever we decide is ok).

I'm in for $316.00, Rob just let me know when you want the check sent.

Folks- I'd like to suggest that we go with the CM-threegroove,pre-fit for the CZ550 with out muzzel break threads. This is the $319 option. I think this will cover most peoples needs and those who want a Brake can have one installed by their gunsmith or perhaps Bearclaw or I will do it for you. This way we will have the largest number of barrels made exactly the same way. If other want to change the barrel threads, use SS etc. they will have to negotiate a separate price from Pac-Nor. If this makes sense, please E-mail me that your in. Include your shipping address and I'll let you know where to send the check. I'd like to get this rolling by 10/15 if possible. The barrels will take 8 weeks to manufacture by the way.-Rob

Yes, I am in.

Yes indeed.

I am tempted to try a finished rifle without a brake just for giggles. If I can't hack it, then I will join the brake crowd.

Folks- Just talked to Dieter- Horneber and he will make 600 Overkill brass from the CAD drawings Fritz454 and Ming provided. Dieter will get back to me on the cost and timing later.-Rob

Email sent. Now I need to get the other stuff.

Rob, any idea where I can get a barrel recoil lug?

I'll be in for the brass also.

Rob,

Sorry for not responding sooner. I've been flat on my back with a back injury for a week now. This is the first day I've been able to sit up. I am in for a CM 28" threaded and chambered, for the $319 price. I will be sending an email as well.

I expect to get the reamer any day and send it to Pac-Nor. Once we see exactly how many folks are in on this I'll place the final order for the barrels with Pac-Nor.
One piece of new data is that I had a conversation with Dave at CH4D and he confirmed that the rimmless belted 600 in their catalog is in fact a .50 BMG derivative with a belt swaged into the case. Apparantly, this was designed by DKT before they went under. It went nowhere.
The 600 Overkill design at least so far remains original.-Rob

Rob, do you want the checks sent to your address,or are we all sending separate ones to pac-nor?
300H&H

Is there a reason nesesitating a belt on a .620 calibur BMG based case, or is it just there to show people it is 'powerful'?

In my knowledge(admittedly limited) I can't see a need for it. There would be plenty sholder to headspace on.

Kristofer

KB, I cannot comment on the 600 belted BMG. The 600 Overkill is a rimless, belted version of the 600 Nitro Express. Robgunbuilder and others, feel the need to maximize the frontal area of their projectiles. The case utilizes a 0.64" diameter base, which is the same as a 505 Gibbs. The belt is utilized for headspacing, of course.

I believe Robgunbuilder is limiting the operating pressure to around 55000 psi. This is providing ballistics of approximately 2500 fps with a 900 gr projectile. You know a typical deer rifle.

Axel

Good News - The 600 Overkill reamer and headspace guages arrived today! Everything checks out just fine. I will send the reamer and guages to Pac-Nor with the barrel order. I need to still get a firm response from Dieter Horneber as to when the cases might be available and Ed Plumer is also following up with Bruce Bertram. I expect at least 100 cases should be available from each source for testing purposes. -Rob

Axel, I like bigger bullets, I dont require(nor does any one esle) justification to make a bigger gun. After all, I am American, bigger is simply better.

When I finish my 376(my first real rifle) it will do my killing for me. Untill I get my 416 Rigby and eventually 450 Rigby. Then the 376 will just be my varmint rifle. Hopefully Mingo's 500 Ninja will be a total sucess as I would like to remain rimless and beltless in my cartridge collection.

I know it is correct terminology, but I never agreed with calling a belted round 'rimless'. Belts look a hellava lot like a rims to me and in fact serve the same funtion.

I just fail to see the purpose of a belt being swaged onto a BMG case, when the calibur of the wildcat will leave a large sholder that can easily handle headspace. If they were blowing out strait walled, I can see the need. On a 600BMG I do not see the need for a belt, and it is an extra step in making the cases.

Does it serve a purpose I dont see, or is it just their to look good?

Kristofer

[ 10-09-2002, 07:56: Message edited by: KBGuns ]

KB Guns- Apparantly DKT deceided to use a shortened version ( 3.0 inches) of the .50 BMG case for their .600 and deceided to simply headspace off a belt swaged into the case. CH4D apparantly made swaging dies for this conversion and it apparantly did work. It would appear that not a whole lot of thought went into the case design. The only advantage I can see is that by using a belt, the fireforming of such a shortned cartridge is greatly simplified versus the alternative of trying to headspace off of the case mouth for fireforming and .50 BMG brass is cheap and of high quality. Given the need for a hydraulic swaging press I personally don't understand why this was done. Nevertheless thats the situation.
The other .600 varient I am aware of was also built on a shortened .50 BMG case . This headspaced off the shoulder,but the entire case was swaged down so that it would fit in a M98 mauser action. I posted pictures of this case about a week ago
The .600 overkill is a belted version of the full length 585 Nyati basic brass, 3.0 inches long and designed to feed through a CZ550 or larger action. It is designed to exceed the 600 NE ballistics ( pobably considerably) in a practical hunting weight rifle. Those involved in this project also believe that a bigger bullet is a better bullet and are doing this just for fun!-Rob

That makes sence, it would make fire forming alot easier.

Is the 585 Nyati an origonal case or is it built/formed of another cartridge?

Anyway I shure you will have worked out all the details by the time I am ready for a .600. I have already more or less planned my next 5 years or so of firearms aquisition. Tho I gotta admit, I will probly be loading it down a bit, or have a JP recoil eliminatior, on a 60cal that might not look as silly as it does on a AR15.

Just too bad its not beltless/rimless...

KB Guns- The 585 NYATI case is based on the 577NE case. There are many versions of the NYATI out there, however, the most common one uses the 505 Gibbs .640 Boltface and its case is 2.8 inches long.
Bertram makes Nyati headstamped brass that is about 3.2 inches long and is designed to be necked down to form the Nyati neck and shoulder. Interestingly, it will just take a .620 bullet as is. By simply adding a belt, for headspacing and keeping the cartridge length to 3.0 inches, the 600 overkill was born. The COL of the 600 overkill with a 900 gr woodleigh softpoint is 3.600 inches and will just fit a cz550 mag magazine.
Hopefully we will have a few operational 600 Overkills by jan/feb of next year.-Rob

What's the update on the 600 overkill? I am still interested in getting a barrel, but I haven't seen any updates on it recently. Actually the only thing I see on this forum lately are the "Troll" and "Troll Hunter" posts

efryman,
The barrels are ordered, brass order is being put together and the dies are ordered (at least mine are ). If you want a barrel, you better email RGB right away.

If you want dies you better call CH4D right away. He is going to make them next week.

George,

He is cutting the dies next week.

Then they must go out for heat treating. That's a batch thing that only happens so often.

Then they will get boxed and sent to us.