Found a deal on a Mark V in .340 so I’ve decided to build a .500 A-Square and have a couple questions. I need to find a gunsmith to open the bolt face if anyone has a recommendation I would appreciate it. Also it appears properly headstamped brass for this has dried up. I found Bertram makes brass for a .500 weatherby but I have not got a response from them yet on the specs for that cartridge. Perhaps someone here may know a bit about it. As far as specifics I am ordering a stainless barrel from McGowan and will send my action there to be installed. I love the aesthetics of the weatherby accumark so I am trying to emulate that in my build. I chose a fluted #5A Douglas contour if anyone has anything similar I would love to hear your feedback. Thanks

Been on the waiting list from Quality for 3 years for 510 Wells (little difference). Basic brass is available and is easy to form. A head stamp will cost you $258 US delivered. If you get desperate PM me and I'll give you details.

IMHO

Find a cheap 378wby or 460wby to convert. You will appreciate the bigger stock dimensions in handling the recoil. Also, you will not have to open the bolt face and change the magazine box.

Thanks. I am picking up some basic brass off a forum member but still keeping my eye out for some headstamped brass. I thought about getting a .378 but i got this .340 for a song. Found a stripped .378 bolt on numrich might go with that.

The 500 A-Square is a great caliber.

How hot are you planning to run it? It will go over 8300 foot pounds.

Good luck with your project. I am having an A-square built on my CZ by AHR that should be finished fairly soon. I am just going to run the 460 WBY brass and go from there.

416Tanzan, I plan on running 570gr @ 2150fps for a general purpose load. Of course I will have to crank up a few rounds to 8300 ft-lbs just to get the full effect! JMJ888, good luck with your build as well! AHR has a stellar reputation and im sure your CZ will shoot lights out.

My 500 AccRel Nyati was also done by McGowen. Good people. The little Ruger Hawkeye sends a 450gn GSC around 2667fps, crossing 7000 foot-pounds, but my current loads are about 2600-2625fps, down around 6800ft#.

I also use the CEB Raptor-tipped, 360 gn at 2800-2850fps. Both shoot tight little groups at 100 yards. Now it needs to taste some buffalo.

Enjoy your ASquare: test it out and find some accurate hunting loads.

I have often wondered if Weatherby will one day introduce a 500 Wby.

Be easy for them as the barrel profile they use on the 460 would be fin for 50 calibre. That would give them every standard bore size from 30 to 50 based on the 378 case.

They could have 570 grain factory at 2500 f/s.

I would think there would be enough Weatherby collectors out there alone to cover the cost of developing a 500. They must have surely known the 338/06 in the Ultra Light would be a limited market but easy to do as they had then in 30/06. I say tye 338/06 would have been a very limited market because I reckon most blokes who are prepared to pay some bigger dollars for a 338/06 would in the main be for the M98 and M70 actions.

Maybe it would upset some blokes who have given Wby a big bundle of money for an all out 460

quote:

Originally posted by Mike McGuire:
I have often wondered if Weatherby will one day introduce a 500 Wby.

Page 414 of Ken Howell's magnum opus shows a ".500 Weatherby Magnum" but it uses a .512-caliber bullet!

Be easy for them as the barrel profile they use on the 460 would be fin for 50 calibre. That would give them every standard bore size from 30 to 50 based on the 378 case.

Calibers: .308, .338, .375, .416, .458, .510 ... A ".475 Weatherby Magnum" would still be needed to fill that HUGE gap.

They could have 570 grain factory at 2500 f/s.

Yep, easy.
The maximum .500 A-Square load in the A-Square manual was for 600-grainer at 2527 fps.
Average pressure for that was 64,000 psi from a 26" barrel of 1:10" twist, using 117.0 grains of H4895.
Their specified MAP for the .500 A-Square is 63,860 psi, mighty close to 4400 bar, for the CIP crowd.

I would think there would be enough Weatherby collectors out there alone to cover the cost of developing a 500. They must have surely known the 338/06 in the Ultra Light would be a limited market but easy to do as they had then in 30/06. I say the 338/06 would have been a very limited market because I reckon most blokes who are prepared to pay some bigger dollars for a 338/06 would in the main be for the M98 and M70 actions.

Yep, I had one of those Ultralightweight MkV .338-06 rifles.
For some reason I traded it off and ended up with a Modelo Argentino .338-06.

Maybe it would upset some blokes who have given Wby a big bundle of money for an all out 460

Maybe.
I met Art Alphin at a Shot Show and he pissed me off.
So I had a .500-A2 built and had it engraved: ".510/.460 Weatherby Improved Jenkins And Berry" and called it a ".510 JAB."
It has a 30* shoulder instead of the 35* shoulder of the .500 A2.
The throat was lengthened enough to seat the .510/750-grain A-Max out to 4.75" COL.
It is a wildcat, but standard .500 A2 dies work just fine to load its ammo.

John Buhmiller did it decades before Art Alphin.
They should have called it the .500 Buhmiller, of course.
And how about that .50 Peacekeeper of J. D. Jones/SSK? He liked 23" barrels of 1:10" twist.
There have been lots of copycats of John Buhmiller's cartridge.



The take-off barrel above is the .510 JAB, formerly on a BRNO ZKK-602, 23" long and 1:10" twist, stainless McGowen, Cerakoted.
The barrel on the Mark V is now a .510/.338 Lapua Magnum Improved (2.700" case),
aka 12.7x68mm Magnum (Hornady Custom die name),
aka .500 Bateleur, with 25.59" (650mm) long, 1:12" twist, stainless McGowen.

The muzzle brake adds two inches to either barrel when installed, both are rather heavy target contours.
.510 JAB was 0.850" diameter at 23" muzzle, rifle weighed 10.75 lbs in a McMillan BRNO/CZ stock, magnum filled.
The MkV 500 Bateleur is 0.915" at 26" muzzle before cut and crown, rifle weighs only 10.25 pounds as shown
(B&C Medalist/Wby factory stock), muzzle heavy.

Maybe I will find a gunsmith who will install the .510 JAB on another action,
there is enough room on the knoxform to preserve the fancy engraving, even if threads are whacked off and it needs re-chambering.
We have access to reamers for
.500 A2
.510 JAB
and .500 Jeffery plus .510-caliber throating reamers.
If it is getting set back, could even do a 500 Mbogo 3".

I have another 500 Bateleur with Pac-Nor No.6 sporter contour, also made by McGowen, 24" length, stainless 1:12" twist.
It is 0.790" in diameter at its 24" muzzle, threaded for a Vais brake!
That is as light a barrel as I would consider for a .510-caliber bolt action.
That FN Mauser, with 3.5"-long Wiebe drop box and a B&C Medalist stock, weighs 8-lbs 11-oz wearing only a set of Weaver steel bases.

I do have one rifle that finally got stamped simply "500 A2."
It is a Ruger No.1 with another McGowen barrel that is 1.000" in diameter at the 27" muzzle.
It has a 6"-long cylindrical knoxform, straight taper after that.
That Ruger No. 1 in a B&C synthetic stock weighs only 10.5 pounds wearing only a steel Picatinny rail
and a custom muzzlebrake, flush contoured and extending barrel overall length to 29".

Pac-Nor No.6 sporter contour or heavier is my recommendation for barrel on a .510-caliber bolt action.
1:12" twist is how I ended up building them after starting off with 1:10"
and even tried 1:9" twist on one of my 500 Mbogo rifles.

Rip ...

Ron,

You need a 500 Nitro on a Number 1 to complete your 50s.

If you made 500 Nitro Improved that would be like a rimmed 510 JAB unless my memory of the case head (in front of the rim) diameter is wrong.

Rip, that is a very nice rifle! I love that green B&C stock. is there any reason you've come to prefer the 1:12" twist? just curious as I ordered a 1:10"

quote:

Originally posted by Mike McGuire:
Ron,

You need a 500 Nitro on a Number 1 to complete your 50s.

Yep. Like I need a hole in my head.

If you made 500 Nitro Improved that would be like a rimmed 510 JAB unless my memory of the case head (in front of the rim) diameter is wrong.

Now you got me interested!

A .510/460 Weatherby Improved Jenkins And Berry RIMMED!
I might find a use for that fancy-engraved barrel yet by stamping "RIMMED" at the end of that string.
AKA the .510 JABR, prounounced: "Five-ten Jabber."
22"-barreled .510 JABR Ruger No.1, about the same length as an 18"-barreled bolt action.

Rip ...

quote:

Originally posted by victor1050:
Rip, that is a very nice rifle!

Thank you very much. (That's my Elvis impersonation in English.
In Afrikaans language it is: "Buy a donkey.")

I love that green B&C stock. is there any reason you've come to prefer the 1:12" twist? just curious as I ordered a 1:10"

Well, early on here, a lot of "naysayers" (I make air quotes with fingers when I say that) spoke disrespectfully of 1:10" twist.
These "experts" were actually just a bunch of bubbas who wanted to use a 1:15"-twist milsurp/scrap 50 BMG barrel
turned down to build a 500 A2.

In general:
The 500 A2 will do about 80% of the velocity of the 50 BMG, therefore about 64% of the Kinetic Energy of the 50 BMG,
in a rifle less than 50% of the weight of the 50 BMG,
and with a significantly shorter barrel.

That comparison is with firing the same bullet, let us say a 700-grainer for comparative purposes.

So, 50 BMG 700-grainer at 2750 fps is typical.
In the usual 1:15" twist it is spinning the bullet at 2200 RPS.

The 500 A2 is not hard-pressed to do 2200 fps with same 700-grain bullet in a barrel about a foot shorter.
1:10" twist >>> 2640 RPS, more than fast enough, better penetration with FN solids at close range (more stable in air to meat transition)
1:12" twist >>> 2200 RPS, same spin as in the 50 BMG "target rifle" plenty fast enough with shorter hunting bullets
1:15" twist >>> 1760 RPS: Bubba's 500 A2 is gonna be inaccurate, only saving grace is it might do better with cast bullets at low velocity.

1:10" to 1:12" twist is best, IMHO.
The 1:10" will allow you to slow the 700-grainer velocity down to 1833.333... fps and have the same spin rate as the 50 BMG "target bullet."
BTW, those 700-grain AP, blacktip bullets are pretty accurate. I used to buy them as pulled/surplus bullets for 35 cents each.
Some had Bubba's plier marks on them, but they shot well.
705-grain AAA Harlow "target" bullets (monometal copper, moly-coated) were a little more accurate, at less than 2200 fps
in a 1:10" twist like my Ruger No.1 500 A2:







Rip ...

0 -- run away, take a nap, over tip the bartender ,anything but take on this project - you've been warned -- this one is big enough to teach you all the lessons why big bores suck to build

1: have mcgowen install the barrel, bolt fact, chamber, and feeding

2: have you considered adding a third lug to the barrel? there's at least 10 ways, i prefer a integral lug cum rear sight base

3: make certain your chamber reamer and reloading dies agree on the print

4: don't even remotely sweat "headstamped" brass, unless you are planing to take it out of the county -- brass pops up from time to time, but many times of questionable sourcing --

5: NORMA brass - order yourself a mess of 460 ww made by norma -- like 120 piece ..

6: harbor freight mini chop saw, add a "tail stock" for trimming your brass

7: there's little need to go past starting loads - BUT, i use h335/TAC for giant cases, to keep the charge weight down for results .. when you are 125 vs 105 gr of powder, those 20 grs do matter in recoil

8: buy/lease/buyback/leaseback someone else's project .. scratch the itch to see if you have it covered, otherwise RUN from this .. this way lies madness

I agree with many of Jeffeoso's points.

However, on powder you do not need to be limited to H335 ball powder.

I would try out faster powders like H322 and H4198, both of which are stick powders and relatively temperature stable. I use H4198 with the lightweight all-brass CEB and H322 with the GSC450.

The McGowan "barrel-knuckle" is great. It is a base for the rear open sight on top and a barrel lug underneath.

In terms of "buyer's remorse" a person should determine what level of power they want to hunt with. If you don't plan to hunt with 8000+ foot-pounds, then consider a 500 AccRel instead. That is the process that I went through.

The 500 AccRel (Nyati) will do over 7000 ft#, so it does everything that a factory Gibbs, Jeffrey, or 500Nitro does, and more, but does it in a smaller package. My Ruger Hawkeye handles the loads nicely, gives every assurance that the round has fired when it fires, and is reasonably compact for carrying. I ended up with a 22" barrel and I think that it works well with the powders I'm using but I haven't tested or calculated what the powder burn percentage is.

One warning: be careful in bedding the stock. I busted two stocks before I got it right. If money is not object ($1000-2000 and up for a stock), then consider sending off to someone like Accurate Innovations. On the other hand, my Hogue handles the 500 fine and is my back up. I had to sand the pistol grip down so that my hand would lie in a traditional position and my trigger-finger wouldn't get whacked during recoil. I even successfully put a reinforced bedding compound receiver for the barrel lug in the plastic-rubber forrearm of the Hogue stock. It holds, though I have two little all-threads running along the barrel channel and bedded all the way back to the beginning as extra support. Someone warned me that without that the front barrel-lug bedding might rip out of the channel under heavy recoil.

Jeffe, thanks for the advice but I might be in too deep now! I am considering a third lug will look into it with mcgowen. Dan there said they will not open the bolt face and I will have to have another smith do it, but they should be able to do everything else. I ordered a 'factory new' .378 bolt from numrich. we will see how it looks when it gets here! I would think mcgowen would not have a problem with lapping a new bolt. 416tanzan, I think the powders you and jeffe mention will be perfect for the level of power I am looking for. I have seen quite a bit of load data here and there, I also have quickload so that helps too. FWIW my plan is to fulley bed this in a factory weatherby bell & carlson. The picture of RIP's rifle above is pretty much what I would like to end up with. Baby steps. Gotta wait for the bolt and send the whole mess to mcgowen and see what Dan thinks.

Yep, you are hooked.
Loading a 500 A2 is very simple.
450-grainer: Benchmark or IMR-3031
535-600 grainers: Varget or RL-15
640-750 grainers: H4350 or IMR-4350

Start with 105 grains of each of those powders in those bullet weight ranges, 100 grains to start if on the heavier side of the range.
Work up until it is satisfying.

The one-holer with the 705-grainer was done with 110 grains of IMR-4350, a moderate load.



I used up all my old IMR and ReLoder powders and switched to more ThermoBallisticallyIndependent Hodgdon Extreme powders:
Benchmark, Varget, H4350.



50 Peacekeeper and 500A2 are two peas in the same pod, performance is same.
Here they claim that a 23"-barreled 50 Peacekeeper gave about 86% of the velocity of a 50 BMG of unspecified barrel length.
That was with a 647-grainer.
That would be close to three-quarters of the KE of a 50 BMG from a 50 Peacekeeper/500A2:



23" barrel is about 100 fps slower than 27" barrel with most loads.



That is the soft-tanned underside of a bison robe that the two rifles rest upon,
taken with the 23" barrel and a 570-grain Barnes XLC at 2400 fps MV, impacting at 50 yards, double lung broadside.
Did not exit.
As the big bull turned and headed north, a 570-grain GSC FN at 2400 fps MV, entered its south end near base of tail, also impacting at about 50 yards.
That bullet exited from the bulls throat, over 8 feet of penetration.
The bull dropped.

I fired another XLC into the bull's chest at 25 yards after he was dead.
Same results, except bullet expanded a little wider.
I fired another GSC FN into the south end of the bull, post mortem, and it exited also,
completing the Texas Tonsillectomy (bilateral excision).



I used iron sights and no muzzle brake on that bull:



Rip ...

Here is the Ruger Hawkeye 500 being fired.
You will note that recoil is manageable.



The shooting was for accuracy, and load development, both of which were successful with .5" loads being determined. Double chronographs are a poor-man's Oehler.

Quick project update. Actions is getting shipped out to mcgowen this week. I ended up using the new bolt from numrich which is great. BTW they have both LH and RH .378 bolts in stock if anyone needs one. Mcgowan is going to lap and true bolt when installing barrel. Also regarding brass, I picked up some bell basic from a kind forum member and formed/trimmed, also picked up bertram's "500 wby" brass. Looks to me like this is .510 wells express judgin by the neck and dia. at the shoulder. Will fireform this when i shoot the gun. Out of curiosity I weighed a few cases. Bell held and avg. of 150.9 grains of water. Bertram was 142.5 grains. will be interesting to see after fireforming. looking forward to getting the barreled action back in hopefully a few months.

pics

Good work.
McGowen is GOOD.
I ordered a .458 rifle barrel on 8-23-2019 by internet.
They called 10-07-2019 (Monday last) and left a message that it was ready to ship.
Just about 6 weeks to make a McGowen No.4 Sporter stainless 1:14" twist.
I called them Wednesday and paid the final payment. I am sorry to have been so tardy.

It will be a lively .458 WIN LongCOL 3.6" on a Winchester M70 Connecticut Classic in a B&C Medalist stock.
I am thinking I will dare to go as short as 24".
I must be getting old and tender-shouldered.
I now prefer a .458/480-grainer at 2300 fps instead of a .510/570-grainer at 2500 fps.
I'll get this .458 WIN threaded for muzzle brake too.
Just for benchrest shooting, not for hunting, of course.

Rip ...

quote:

I must be getting old and tender-shouldered.
I now prefer a .458/480-grainer at 2300 fps instead of a .510/570-grainer at 2500 fps.

Next thing you know, you might think that 330grains at 2600fps is a great all around load (maybe even .416").

Rip. Sounds like a fun project. A M70 in .458 is on my want list! Had a super express in .416 rem I should have never sold. 416Tanzan, my “play” load for my 416 rigby is close to that. A 350gr mag-tip at 2600 Fps. Gonna try that on a Michigan white-tail this year hopefully. Going to try those 330’s eventually. My next loads will be 400’s at warp speed. Gotta get the shoulder ready for the .500 ya know!

weatherby used to make a dropped floorplate for the .460 rifles lets you get one more in the magazine. don't know if they still do but if you find a weatherby dealer, they may be able to help you. last time I tried to source weatherby parts I was referred to numerous dealers by the company.

I think the 500 A2 is a great round. I have a 500 Jeffery, my stock load is a Barnes 570g TSX or Banded Solid at 2300 fps from a 24" 1 in 10" twist McGowan barrel. Have had it up to 2500 fps, but it's much friendlier (from a recoil perpsective) at 2300. Both great calibers as is the 505 Gibbs.

Yep, in too deep now .. this way lies madness!!

try to source yourself some ~550gr cast, pref gas checked bullets ... .512 or .511, dry lubed

the 500 AccRel should have been the shorter throat from the start -- my mistake, but WOW, talk about going big or going home, and trial by fire!!

I hereby proclaim (big pompous radio voice) that the 500 Accrel (original) shall be known as the deepthroat, er, long throat-for-bmg-bullets and that the 500 Accrel Nyati shall be the standard

i designed it to match or beat the 500 jeffery (wells, barnes, a2, whatever same sized case) with a TON less powder... it worked, it's proven.. and it kicks WAy less than my 500jeffe or 510 wells ever did, for same performance

so mote it be!

Project Update: Got the Barreled action back from Mcgowen. Looks very nice. Still needs a bit before the first range trip though. Stock needs inlet work and bedding. I have a Leupold 2-7 around here somewhere thats going on top. I think 4 inches of eye relief should be OK. I also need to order a new mag box and follower for a .460 from weatherby. Thought about a dropbox.. maybe somewhere down the road. Eventually going to get it matte finished with the flute coated just like a real accumark. BTW the barrel is a douglas 5A contour 24 inch length, and the weight at this point is 9.5 lbs. I anticipate the finished weight to be around 10.5lbs.

9.5 pounds ! That fluting makes a difference alright.

Great looking rifle. Nice laser engraving by McGowen.
Yes you need the flat follower and the drop floor plate to get three down in the box + one in the chamber.
Magazine box feed lips may need a little tweaking even if you get a .460 Wby box.
The eventual straight-stack feeding should be faultless.
Excellent progress, congratulations.

Rip ...

That should work!!

i STRONGLY suggest federal 215/215m primers -- hang fires in a 500 SUCK - 2 seconds feels like 10 years!!

you may be surprised at the starting loads -- 500 @ 2100 should be a strong shove, rather than a Mike Tyson uppercut

500g at 2100 fps but a maiden's kiss ...

Winchester Large Rifle Magnum primers also provide the robust fire power of the Fed 215.

Remington magnum are at the lower end and should probably be avoided for a 500 A2.

Faster powders also help, probably between H322 and H4895 (slowest). If you try light bullets, then maybe even H4198.

quote:

Originally posted by chuck375:
500g at 2100 fps but a maiden's kiss ...

uhm... can you introduce me to the girls you hang out with?

Thanks for all the input! I loaded about 60 rounds with Fed 215M primers so I should be good then. I used RE15 and RE17 and will only be around 2100 fps to get acquainted. Then the fun begins!

i'd be interested, if it fits your schedule, for the chrono results on those loads - and how much used -- i have generally been underwhelmed by middle-slow powders in big bores

I would never use Bertram brass.

We have tried several calibers, and all were utterly awful.

Jeffe, I will make sure to do a range report and post my loads. Probably wont be until April-May. I can tell you the first loads will be RE-17 in Bell cases with a 570gr woodleigh. Charge range from 104 to 108 gr. Quickload shows in the 21-2200 fps and 33 to 37ksi. I think it might do a little better than Re-15 in this cartridge. Saeed, I have heard mixed feelings on bertram, luckily I only have 20 pcs to throw away if they dont pan out. I f I need more brass I think I will take Jeffes advice and buy Norma/Weatherby 460's and neck up. Thanks!

Victor,
good luck with those loads making that vel. while the 500 jeffery is a larger case, and i don't have my load books handy, i recall that i was using wc846 and blc2, with roughly 20% more powder to make 2200 with 530 gr bullets ..

the loads will be fine, but *I* would expect the vels to be closer to 1700 than 2200

will be interesting to see ...

remember, if there is a hang fire, keeping pointed at the target, don't freeze up hard, and breath -- and count to 60

Ha. I should know when I pull the trigger wether it’s 1700 or 2200 right? Either way I’m looking forward to getting this beast to the range!

Again, a person must decide what they are trying to achieve.

The 500 A2 is a very large case that could house loads in the range of 7500-8000ft#.
In terms of velocity that means 2500-2600+fps. You will probably need faster powders to reach that.

The good news of this is that faster powders are less prone to hang fires and they can be downloaded fairly safely. At least H4895 has a reputation of being usable at 60% of its max load.

So if you are aiming at a sedate 2200-2300fps, then I would check out powders at H4895 rating and faster (H-Benchmark and H322 [both extruded and relatively temperature insensitive]).

Let's extrapolate. One published load gives 115grain H4895 with 600gn bullet, 2474fps, 8158ft#, and 61,600psi. That will get the shooter's attention. Less is probably more, in this case. For your 570gn bullet, already less, you probably want 100gn H4895 (~2220fps) up to 114gn (~2500fps). I would do a ladder test with any of these powders because capacities around 100 grains might uncover some irregularities in burn rates. Afterall, 100 grains are two to three times more than the cartridges commonly used. For h4895 you might load 93gn, 96gn, 99gn, 102gn, 105gn, 108gn. See what you get. You could do the same with BENCHMARK, maybe dropping 3gn at each stage.

I have always used Reloader 15 with excellent results.

Depending on the lot, 110 to 112.5 grains will get you 2,500+ fps muzzle velocity with Barnes 570 grain bullets. Start lower and work up.

8,000+ ft.-lbs. of muzzle energy.

I have used that load to devastating effect on elephant, hippo and Cape buffalo.

It is the hammer of Thor.