I currently have a CZ-550 at the gunsmith's being converted into a .510 JAB, .50 Peacekeeper, .500 A-Square IMP, .510 Wells, ect, ect. and am excited for it's completion (even though I know it will be many months from now).

**I am still however looking for a round that I can seat a .510 BMG bullet on and feed it from the mag.**

Originally I was thinking of .416 Rigby brass in a 30 carbine look, but ran into headspaceing problems (off case mouth, bad idea). So I decided to go another route...

The canalure of a BMG bullet is 1.55" from the tip of the bullet as measured on a Ball, API, and APIT bullet. The OAL is between 2.27" & 2.285" of these three bullets. The max OAL a round can be in the CZ-550 action is 3.75". If I use .500 A-Square brass and shorten the brass OAL to 2.1" while keeping the same neck length (.4") and almost non-existant shoulder length (.022"), you could seat a BMG bullet at it's cannalure and feed it from the mag because it's OAL length would be between 3.65" to 3.70" ( 2.1" + 1.55" = 3.65"). I'm guessing that the powder charge would be between 70gr to 80gr depending on the powder used. The intended bullets would be BMG Ball, AP, API, APIT, M1 Incendiary, and Tracers. Regualr hunting rounds could also be used with little trouble. Quick summary:

- Shortened .500 A-Square brass
- CZ-550 Action
- OAL of loaded round = 3.65" to 3.7"
- Loaded with 619gr to 813gr de-milled bullets
- Powder charge estimated between 70-80gr
- .510 BMG bullet tipped round able to be fed from the mag

Even though I know it will be a much reduced velocity round than my JAB will be, that will be the tradeoff I am willing to live with. Similar to why people get a .22 Hornet and not the .220 Swift.

My question's are these:

1) Has anyone done this or anything like it?
2) What are SWAGS as to the MV of a 700gr round?
3) Any recomendations as to help or pitfalls this round may have?

I have a real appreciation of .510 firearms and can't get enough of them. Now I'm looking for something different. I really appreciated the feedback on the .416 Rigby/.510 idea which proved it a bad idea. So if this wouldn't work, please don't spare any comment, my feelings won't be hurt but my knowlege will be broadend. Thanks

BMG,
We can refer to the full power cartridges as the ".510/460 Longs" as a generic term that would be more easily recognized by the public. My 510 JAB is a variable throated .510/460 Long copied from the 500 A-Square, as is the 50 Peacekeeper.

What you are proposing might be called a ".510/460 Short." Really the same thing as the 50 Whisper of J. D. Jones and SSK. Perfectly good idea with the VLD bullets, or for plinking with milsurps. Sure you could feed them from a CZ 550, but I don't know if the loads would be hot enough to ignite the tracers. I don't have access to my vast library at present, but maybe "Cartridges of the World" has some specs on the 50 Whisper. You might come up with something a bit more powerful than the 50 Whisper which was designed to be subsonic.

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Good huntin' and shootin',
RAB

JD Jones wrote an article about several of his wildcats for the 6th edition of Cartridges of the World (1989) which includes
his 12.9x50.8 JDJ. This is the .460 Weatherby case shortened to 2" with what looks from the picture to be about a 9/16" neck. He also rebated the rim to standard belted mag dimensions so he could make it function in an XP100. Here's a short quote:

quote:

---

I'm not sure what it will do -- I quit at 1800 fps with the 600-grain Barnes. It was a challenge getting a slightly over 5-pound gun including scope to stay together and be realistically shootable. So far it is most accurate with cast bullets of around 550 grains at 1600 fps. . . From this point, increasing power builds recoil at a considerable rate.

---

I think I have read a more in-depth article on this particular gun, but can't seem to put my fingers on it right now. I seem to recall they had a very difficult time keeping the stock in one piece for more than a couple of shots.

Thanks guy's. (Ron, I'll cut out the metal disc that sheilds the tracer compound on an APIT if it doesn't light. On a regular tracer there is no disc, it is just tracer compound. I'll let you know if it lights up when the .510 JAB is done.)

I found this on the SSK web site: "XP-100s can be had in calibers including the 2.5" 460 Weatherby case opened to 50 which is capable of 1900 FPS with a 600 grain bullet from a 13" barrel."

This seems a little much from a 13" barrel, but with the right bullet/powder combo, who knows. I also found a pic of it on his site http://www.sskindustries.com/cart_pics.html it is in the lower left and is labeled the 50 Whisper.

**SIDE NOTE**
SSK has two rounds listed that fire a .510 bullet and are called whispers (1) The 50 Whisper with a 2.5" case which is a shortened .460 Wby case with a rebated rim fired out of the XP100 pistols with 13" barrels that Cannon spoke of and (2) The 510 Whisper which is a shortened .338 Lapua case (looks like 2" or shorter) fired out of a rifle in a sub-sonic configuration on the Sako TRG-S action & stock.

The way I figure it is this, if the 50 Whisper WITH a 13" barrel gets 1900fps with a 600gr bullet, then the 50 Whisper with a non-rebated rim (aka. normal .460 Wby case bottom) shortened to 2.1" including a .4" neck length and a 24"-25" barrel should get at least 2100fps and with a 700gr should get 1900fps.

Am I way off here or somewhat close?

BMG,
I take those SSK velocity figures with a large dose of salt. I don't know. I would expect high pressures if such short barrels produced such velocities with 600 grain .510 bullets.

The 510 Whisper is based on Lapua 338 Lapua brass? Does that mean if you shorten the brass enough you have enough case diameter back dy the case head to form a shoulder to headspace on. The Lapua is really a 416 Rigby case that is a bit more heavily constructed. This would be the same thing as the 50 Oxen would it not? I dunno.

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Good huntin' and shootin',
RAB

Ron,
Yes the 510 Whisper IS based on .338 Lapua and can be seen at http://www.sskindustries.com/riflecartr.html down at the bottom and on the left. Not much shoulder to headspace on.

I talked with someone that has a 510 Whisper (based on .338 Lapua) in an T/C encore configuration. It is 20" with a SS barrel that is 1:10 twist, 8-9lbs with a 10x scope, and shoots 750gr A-Max bullets 1050 with 27gr of H110 powder. This (the Lapua brass round) is designed to be subsonic and that is the way he shoots it.

I am going to call JD Jones and see what he says his 50 Whisper (the .460 Wby brass round) is capable of in a rifle configuration. If it does sound viable and something I would want, I'll have to get with Dave Manson and see what can be done.

BMG,
That stubby 510 whisper has the bullet base in contct with the primer flash hole ... just kidding. Well, at least they have a visible shoulder to headspace on. Hardly possible with a longer cartridge case and any taper at all.
An interesting page. But the rifle they want $3000.00 for is a single shot pushfeed with a tank brake on it. The Accubrake style muzzle brake (a la Weatherby) that is removable and a CRF action make more sense to me. Then you can hunt with it as well as plink with it.

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Good huntin' and shootin',
RAB

Ron,
I agree with the brake & action being poor choices for that money. Ahh the hunt continues. I'm still going to call SSK and try and get info on the 50 Whisper (460 Wby shortie) in a rifle, not their XP100 pistol, setup.

BMG,
The Ed Brown single-shot action for the 50 Peacekeeper seems to have a magazine repeater by Ed Brown proposed for availability through SSK. I don't know if it exists yet.

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Good huntin' and shootin',
RAB

I do not doubt that there is a repeater for the 50 PK, but in 'hunting' bullet lengths.

If it was for the HV & VLD bullets such as the A-Max, AAA-Ammunition 705gr, and mil-surplus, that would be another thing. It would need a mag length of around 4.5" or so for that.

A CZ-550 mag length is around 3.75" or so, which allows plenty of room for hunting bullets in repeater mode, and VLD & HV in single shot mode. (As you know because you have one) Have a good one,

BMG

ps. Your smith has (10) AAA-Ammunition 705gr Harlow solids (the same ones I use in 50 BMG 1000yd competetion) from me at his place in TN. I sent them with my rifle for the .510/460 long conversion. You should get better ballistics & accuracy than with the A-Max bullets.

BMG,
So there is no Ed Brown action with a 4.75" magazine box? I suspected as much. The CZ 550 is the best way to go. I will be visiting Kevin in a week or so. Thanks.

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Good huntin' and shootin',
RAB

I own an encore in 510 whisper as described above. I am still looking for a good cast bullet for it. I have a 975 GC pointed tip bullet mould on order from CBE in Australia. Anyone else shoot this cartridge? thanks.

Ron,
I don't know if there is one or not for sure. If there is, I haven't heard anything about it. There may be, I'll ask on Monday when I call them.

Ranb,
I've heard discussion's of cast bullets in .510" & .512" but either they mold their own or have someone they know mold them. Also, you are the only one I know that shoots the 510 Whisper. For discussions sake, how fast have you pushed yours with a 750gr A-Max or any mil surplus?

I have only loaded for subsonic so far. Pushing them faster will only hurt my shoulder more. 27 grains of WC 820 gives me about 1050 fps.

BMG, hello this is a very interesting post. I have a CZ project for a 50 peacekeeper that I am doing for my dad and he wanted to know what everyone was talking about. I told him that I read your post and he wants to know the out come.

I talked to him and said that since we are going to Prescott Az when it cools down to blast some pierre dogs, we should stop and look at the Wells sport shop in Prescott at there actions I called and talked to there barrel maker and he said a custom action .75" longer should handle the 50.PK. The only problem with the Wells is the cost. I have to get a new cartridge of the world book so I might be asking a question that already has an answer but is there any merit to shorting the hi pressure 505 gibbs or 585 nyattie (I am sure I spelled it wrong ). Could you make up for some of the lost capacity for the 2.1" approx with the larger case, and no rim and belt to stop feeding. Anyway I will be looking for some final field results. RNS