Here are some pictures of the .600 Overkill. For those of you new to this, I invented this cartridge which is basically a belted .600 NE designed to fit and feed through a CZ550 action and operate at over 50KPSI. That goal was achieved, but a CZ550 will only hold two cartridges down and it's a tight fit with only about .015 clearance through the action ring. The barrel is a Pac-NOR custom three groove barrel which we designed to minimize pressure . The idea was generated on this site well before the Trolls moved in, when folks helped each other and we tried to get along with each other for the most part. The project has been over two years in its completion mostly getting the cases made by Horneber. We first demonstrated the doability of this cartridge with homemade Lathe turned brass cases which ultimately saved the day when it came to dimensioning the drawn brass cases shown in the third picture. This one is on Granite Mountain Action. I did all the machining/chambering/gunsmithing/blueing etc. AHR did the stock! It weighs about 13 lbs and is deadly accurate. It will hold three down and one in the chamber. Case capacity of the .600 Overkill is 218 grs of water( slightly more I believe than a .600 NE but not enough to matter)( Ed Hubel-Neck diameter of a loaded round is .644) and Max load so far is 156 grs of H414 with a 900 gr woodleigh. Recoil is stout but more of a big push than a kick. It will literally split a 12 inch oak log with one shot! I'm quite pleased with this level of performance. Feeding and extraction are flawless and there is no evidence of case sticking. For those who ask how fast will it go? I expect 2400fps will be easily obtainable. I also have a 3.2 inch version known as the .600 OK-2 which should satisfy even the most crazed of you! I intend to take this Elephant Hunting next year. At least 1 .600 Ok will make it to Africa this year and we will await the performance results.!-Rob

Rob, how loud is it with that monstrous brake on there? I'm assumeing you won't be wearing ear plugs while Hunting. I have a TC in 309JDJ that is a blast to shoot, but I shot it while hunting and the blast was painful for a couple of days afterwards.

LAR45- When hunting, I've never had a problem with muzzel blast from a braked gun. Without a sound meter I really have no way to compare it to anything. You have to remember that the recoil of this thing can approach or exceed 200ft-lbs and without a brake it might be physically dangerous to shoot at full power! There is no choice but to use a brake. I don't recolect that its really that much louder than a 500 Jeffery or 500 A2. It's burning about 50 % more powder though which makes the brake much more effective. I can shoot this thing in shirtsleeves with no ill effect.-Rob

SWEET!

psychotic. :-) How is the accuracy? (i'm not talking 1/4", real hunting type accuracy, like 2-3")

Red

Dago Red- I have not shot this one enough to know yet but it appears very good. My CZ550/.600OK will hold 2" 50 yrd groups offhand with no problems. Basically as good as I can shoot open sights. These guys are balanced very well and shoot nicely offhand. They are made for hunting and shooting offhand not for benchwork. That would not be something I'd look foreward to.-Rob

You are the best gun builder the world have ever seen! How much does it cost to build another one just like that? Are you going to patent your cartridge design? The only way to protect your design is to patent it.

"That's a HUGE BITCH!!!1"

Very nice, can't wait for reports about performance on critters.

Rob- Can you give me some specs on the GMA action. Like hardness ( is it casehardened; what surfacehardness/ what corehardness?), mag.dimensions, is the left locking lug splitted like a mauser 98 or not?
I have tried to reach GMA by e-mail but obviously the adress is wrong because the e-mails are returned to me..
Hope you�re able to help.. Thanks !

Dr. UH-

It is difficult to catch Mike because he travels a lot. Your best bet to catch him is to call his cell phone. You may also want to talke to Fred Wells because he is the principle designer of this action and I am sure he can be much more helpful than Mike from Granite Mountain.

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Rob- Can you give me some specs on the GMA action. Like hardness ( is it casehardened; what surfacehardness/ what corehardness?), mag.dimensions, is the left locking lug splitted like a mauser 98 or not?
I have tried to reach GMA by e-mail but obviously the adress is wrong because the e-mails are returned to me..
Hope you�re able to help.. Thanks !

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That is a great looking rifle.



It is a rifle that would be offensive to many people



Mike

that is one sweet looking rifle,my hat is off to you!

Shiiite!

Ulrik- I have all the info on the GMA action. If memory serves its made of a 8600 series steel, been heat treated and drawn to RC 42? It is not case hardened. I'm told this series of steel can be case hardened but I chose not to do that. I'll confirm that later. Surface hardness is obviously quite high as I had to use carbide to fly cut the square bridges. They were not truly flat when I got the action. To be honest their were a number of things wrong with the action when I received it. It would not eject properly as the slot on the bolt was not cut deep enough to allow the ejector blade to extend far enough. Interestingly that was a common flaw in WWII mausers made in concentration camps. Basically it's a copy of a Brevex magnum mauser action made of modern steels. The bolt has a diameter of .740 and the mag box is huge.To work with this cartridge you have to have the guts to mill out( again carbide only) a BIG scallop out of the right rear action ring and spend lots of time on the feeding ( The action costs about $3500 now). These cartridges must be positioned tightly up against the right and left rails and shoot straight into the chamber. The threads are not1.100X 2mm like on the brevex but rather1.150X 12TPI , 60 degree (as I remember), I also think the tenon is longer than the std Brevex. ED at AHR now has GMA actions. After I built this one and sent it to him for stocking, he agreed with me that this, the johansen, original Brevexes and Vektors are probably the best actions to build really big bore guns on. AHR will now be offering their 500 AHR's and up with GMA actions. IMHO that's definately the way to go assuming you can afford it. -Rob

Rob, thank you for the pics. That is wonderful work.

Do you know if anyone else in the original dirty dozen who ordered barrels from pac-nor has finished their rifle? (I remain in the recalcitrant crowd.)

Rob, in a word, WOW! A very fine firearm. Now, just out of curiosity, could I (5'-10, 175 lbs) or someone like me be physically able to handle such a gun? I don't think I'd ever own one, I'm not really inclined to go after an Ele, but I might change my mind someday. Still, I admire the work. Congrats!

Rick

Rob,
I have a question:

Where the hell in/near Las Vegas was this photo taken? I've been there, even flown around it in a helicopter, and never saw an area as verdant as this (not counting the golf courses).

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GeorgeS- I wish Las Vegas looked like that! Could you imagine the WATER BILL?No, It was taken at my buds house outside of Reno! -Rob

500 grains- I hear one more is almost done and a second in progress .I expect most people wanted to wait till we received the drawn brass. That was probably a good thing as we learned alot in the process such as what actions were best and how to tame the beast! This one is the model we'll use for GMA guns. The only change I'd make in the future is to have the reamer reground to reduce the neck diameter as the Horneber brass is thinner in the neck .012 versus the original plan for .015-.016. The final case dimension is probably a little better as the taper is increased slightly. It's always easiest to start with a case and work backward than the other way around.-Rob

Thanks. The reason I asked is that my wife and I are considering moving to LV in five years or so.

George

George- Buy NOW! House prices are moving upwards big time. In the short time I've been there, house prices have increased about 14%. Vegas just keeps growing! The summers are HOT though!-Rob

That seems like overkill!

I don't personally like brakes but can see why you'd need one on this beast. Nice looking gun anyway! Good luck making it to Africa!

Rick- In a word yes! You need some basic training on how to cope with heavy recoil and you must never allow your head to come OFF THE STOCK. I repeat recoil is not a problem and I'm only 5'7- 175lbs. Size has little to do with it!-Rob

Rob, Outstanding job on the .600 Overkill, and you went the extra mile to develop the brass and a better action for this monster cartridge.

A couple of ??? You indicate that due to the tight tolerances, the CZ550 action is not the best aplication, so you went to the GMA action. Is this about a $2500-3000 increase in price over the current actions that AHR now sells?
Also, it appears the brake is not the removal type. In your estimation, without the brake does this almost make the rifle unuseable for hunting? For example 900 grainers at 2150-2200 fps?
Finally, is the brass going to be a stocked item available fromm a source without special order from Hornberger?

Great looking rifle and it shoots too!!

Dakota- To be clear the CZ550 will work but will only hold two down and one in the chamber. Tolerances are tight but it does work. It actually is easier to get a CZ550 to feed than a GMA. I actually bought the GMA for the .600 OK-2 which is too long for the CZ550. I deceided to use it first for the 600OK-1 to learn what tricks are necessary. Yes it's pricey, but have you looked at a Johansen? The Brake is removable and threaded on. I am pretty good at taper turning and you do have to look closely to see that it's just not one piece. If you want to shoot the gun without a brake just keep to the 1950 fps level and basically duplicate the .600 NE. 154 grs of IMR 7828 duplicates that round nicely. It will still take down a dinosaur even with that puny load! Just watch a Mark Sullivan video for the effects!
Brass should be a std item for Horneber once he has finished my order. Althouh he will probably only make one run/year Lathe turned brass is available from Bridger Bullets and works well at the 1950 fps level. I expect that many folks will order this brass to build a number of wildcats on. As for patending a cartridge, there is apparantly no way to do this. It's registered, butanyone can make even the smallest change change the name and claim it as their own. People in fact have done that already with this cartridge although none have access to drawn brass yet. I have been asked to do a write up on this for Cartridges of the World and ken Howells new book.Maybe Guns and Ammo will get interested too! That would be cool! -Rob

Rob
You do fantastic work! I wish I was half as talented. Can you use one of these actions to build the 600 OK?
http://www.gunbroker.com/auction/ViewItem.asp?Item=15449636
Im getting started on an enfield but she wont be that big. I would like to try something in that league but only after I work up to it.
Dean

GeorgeS, if you are looking for slightly more verdant near Las Vegas, consider the area around Mount Charleston. Trees, grass, more rain, snow (oops), etc.

I left Las Vegas in 1977, but my parents are still there and I get by from time to time. I hear the wild building craze has made it almost all the way out to Red Rock Canyon State Park (maybe 20 miles from downtown), and is getting closer all the time to Mount Charleston, which means the basic amenities are probably getting pretty close by now...once they started putting casinos on Rainbow we knew it would never be stopped (until the water truly runs out).

The case head on the 600 Ok is the same as the 505 Gibbs or 585 NYATI( nominally .640). I am sure you could use the Ultramag action or a 1917 Enfield with a P-14 bolt. I'd expect the ultramag would have the same capacity as the CZ550. The enfield or better yet a Model 30 express action would actually work( although I'd get it re-heat treated first) and it has the advantage that good large capacity mags are available from Blackburn. Expect to put about $1500 in gunsmithing one though!The Ultramags are rough looking actions I have to say!!-Rob

Rob,
Looks great!
Ed was having a bit of trouble getting the CZ550 action to feed the 600, but he tells me the problems are solved. I guess it would be best to go with the GMA, but last time I checked I was still a college student and MUST stick with the CZ.

Regarding mag. capacity...have you heard any news from John/Bridger bullets about the schuler-type mag boxes? I suppose he's busy with the bullets, but I hope that's an option in the future for the CZ. (A 3-4 shot mag box in the 600 will reinforce the Overkill image )

Awesome rifle. Keep up the good work. People call me crazy with a measly 416 Rigby. This is a great place!!!!!!!!!!!

Hi Rob,
As expected you've taken this project above and beyond. What a beautiful rifle. It just radiates the essence of the meaning of big bore. You look at that rifle and you just know big things are going to happen. I hope I get a chance to visit Vegas and touch that baby off a couple of times. Very interesting about the Cartridges of The World interest. I hope it works out really well for you as you've put a lot of work and time into this one. Am I really two years older already? WOW
Take good care Rob,
Dave

Dave- Your welcome to light this pup off any time your in the area. Your 470 MBOGO is probably all anyone would ever need for anything on this planet. In truth I got some of my ideas for this project by following your footsteps on the 470 MBOGO. One of your stocks almost wound up on this project, but the GMA would not fit!!! It's hard to estimate just how much effort goes into projects like these. However it's very nice when things work out in the end.-Rob

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For anybody interested, midway has a "sale" on woodleigh .620s. I forgot to check the other cals, but being that hunting season is over they might drop more...

Thanks, Rob. The most powerful rifle I've ever personally fired was a 300H&H. I don't know what the load was, but I know it almost knocked me over. Of course, I was 14 years old and some 40lbs lighter then, but I haveen't tried a "big gun" since. Sounds like I need to buy a medium rifle and start working up. Oh yeah, I know I have a problem with my head coming off the stock. I need to practice more. Thanks for the info. Can't wait 'til it warms up here in NY so I can start practicing. And that's still a beautiful rifle.

Rick

Rob,

One of the reasons I was interested in the .600 OK is that I have a CZ550 rifle in 416 Rigby and was contemplating restocking this or spreading my wings one last time to get a new big bore rifle. You know the "itch", really no good reason since I already have a 450 and 500, but wanted something in a bolt gun in a larger caliber. Talked to Ed Plummer briefly and mentioned the 470 Mbogo. Possible, but does have reamer, and then he suggested the 600 and I said no way. That was before your success story. A big bore cartidge where you don't get hammered to death

Going to Africa this summer with two of the big bores too, so no need to make a quick decision as it takes time to learn how to shoot a rifle again off hand again, as least for me.

Will eagerly await your loading and shooting accuracy updates as this will help in any decision. Also Ed evidently feels comfortable with the cal.

Good shooting, Dak

Dakota & Rick- The .600 OK may look intimadating but in reality except at max loads it's not! At the original 600 NE power levels it's pretty easy to shoot and I'd hunt any animal in the world with it! My first one was on a CZ550 416 Rigby action and other than the cartridge capacity it worked out quite nicely. Ed at AHR and I have worked together on this for quite some time and we have the bugs all worked out NOW! The original batch of barrels is long gone now, but I have the reamer and guages( which I now can modify to more closely match the brass) and I will make it available to Pac-Nor if others want to order long chambered barrels. I am not a FFL so I won't fit actions , but I can and sometimes do chamber, thread and and fit muzzel brakes and make barrel mounted recoil lugs for folks I trust ( No Trolls or suspected Trolls).
These big straight cases are also very adaptable to cast lead loads and you can always work up slowly. AHR would probably make a turnkey version for around $3000 on a CZ550 and around $6000 for one on the GMA action. If you want any brass Dieter Horneber will be making a big run soon and you might be able to get some Brass by tailgating.-Rob

Rob-I will take 50 cases.I think a whole bunch more folks should order cases, as it is just as easy for deiter to make
3000 instead of 1100. Who do we send money to to get in
on the first run.I am not going to build a rifle for this
but want to help increase the supply of available brass, for
shooters and collectors.I will do my part, how about the rest of you who aren't in already.Ed.

Rob, this thread is more interesting than 90% of the articles in RIFLE magazine, and is more interesting than 100% of the articles in most other publications. I suggest that you get the credit you deserve by putting your comments and a few snapshots and 5 or 6 loads together as an article and send them to RIFLE. This is much, much better than many of the paid articles.

Thanks for telling us about your work.

By the way, what is the possibility of making a 3 round single stack mag for the cz550?