I finally finished this thing and took it to the Range last night. Loads were 130 grs of RL-15 over a 750 Gr. Woodleigh, Fed 215 primers. Lathe Turned cases. The gun weighs 12 lbs and I shot it open sights and with the scope 2.5X20 Leupold. It's homebuilt on a CZ550 action with a #7 Pac-Nor barrel, Two recoil lugs and a McMillan Express stock heavily re-inforced. It also has an Integral Muzzel brake(a bunch of axial holes drilled in the barrel using an indexing head) and ionternally crowned and counterbore reamed at .625.The gun holds two down and one in the pipe but I think with a new follower it will go three.
Shooting Impressions- This thing ROCKS! We firsd about five shots. Accuracy with open sights fired offhand was 3 inches at 100 yrds( nothing closer at this range). Recoil was substantial ( considerably more than my 500A2 with full house loads and 750 gr bullets)but NOWHERE NEAR UNMANAGEABLE. In fact no worse than my light 470 NE in my opinion! It got quite a bit of attention and a Friend of mine worked up the nerve to shoot it and was MIGHTILY IMPRESSED. It was his first time shooting something like this.He said it was one heck of alot worse than his .458 but much more accurate. Accuracy was amazing given the open sights and the range. One recovered Woodleigh was about 1.5 inches in diameter and weighed 488 grs. All and ALL a big sucess.-Rob

What velocity was it...?

Rob how did your .585 perform with your scope??, have you zeroed it??. I have read so many things about poor penetration with this caliber I wonder if these people have used solids (they probably did). Rob what do you think about using the blackpowder 650 grainers for thin skinned stuff??. Obviously you could load a little hotter than what you have tested to date, but I am glad to hear that someone finds it manageable, as my mate and I really want to blast some ferals with ours when there done.

Let us know how the next lot of load developement goes.

Regards PC.

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Welcome to the club!

You can shoot that thing from sandbags just fine. I found that the recoil was easier to manage from bags on the bench than offhand.

Hi Rob,
Sounds like fun how about a picture of the beast.
470 Mbogo

Let's see- Velocity-unknown, estminated at about 2200fps. I'll Chrono this weekend. As for using a scope, recoil was quite managable and I had no problem with using a 2.5X20 Leupold, although I'd not use a scope with shorter eye-relief. You have to pay carefull attention to how you hold it with a scope! Given this level of offhand accuracy, I'm quite sure that off the bench this rifle is capable of MOA groups. The muzzel break is quite effective and I'm sure nearly cuts the recoil in half.
I'm having trouble posting to Hunting-Pictures which seems to be having server problems. I'll post a picture ASAP.

As for cast bullets, that is definately a good idea for practice loads. I would try paper-patching a 650 gr .580 BP bullet. I don't want to try that in my gun due to the integral Muzzel break, but no problems in a non-breaked gun. I would keep the velocities below 2000fps though.
The single biggest problem remains the brass which has to be Lathe turned ala bench-rest style to fit the tight chamber. If anyone else builds one I would opt for a custom JGS reamer with a straight .612-.613 neck dimension. The CZ550 action works fine and the .640 boltface is not an issue. The action rails need MAJOR work as well as the ramp, but otherwise it's a standard build-up. The Mcmillan stock worked out fine except that the express stock will only accept a number 7 Pac-Nor barrel contour which decreases the maximum weight slightly. It also took Mcmillan 6 months to get me the stock which hung this project up big time. Total cost to me, however, including all tooling was about $1500.
John Ricks also talked me into buying a new
silver soldering torch which brought the cost up substantially! All in All I learned alot and it generally came together pretty well, but this is definately an advanced level project.
Now I need the time to go find an elephant or buff to test it out on. This weekend I'll test it on logs in comparison to my 500A2 a 460wby and .458 Ackley to see what I can learn about relative penetration/wackout power. Then perhaps I'll send it to 470MBOGO for some more thoroughly scientific testing.-Rob

[This message has been edited by Robgunbuilder (edited 03-27-2002).]

[QUOTE]Originally posted by Robgunbuilder:
Good idea
I'll have to notify the tower that the square tube may be reaching lift off.

470 Mbogo

Rob the breaks were having put on our rifles will be removeable, but why can't you shoot the 650 gr Woodleigh BP projectiles with the break on??(Woodleigh have 2 types of 650 gr softnoses the Blackpowder ones and the 650's rated for higher velocities). And why do you need to paper patch them, they are jacketed. We were thinking of driving the 650 BP's at around 2300-2400 fps to try and acheive a high level of expansion on smaller game, do you think this is something we should be careful of??. I hope we can use them we just purchased 2 packets of the Woodleigh 650 BP's there impact velocity rating is 1700-2000 fps. Funnily enough the rating for the normal 650's is 1800-2100 fps not much difference

Hanging out to see a picture of it Rob.

Regards PC.

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[This message has been edited by PC (edited 03-27-2002).]

PC- Sorry I didn't realize that Woodleigh made BP 650 gr jacketed bullets. I thought you were talking about using Cast 650 gr..580 BP bullets. This can be very effective if you put on a .005 paper patch. However, shooting PP bullets out of a muzzel break is a No No. There have been a number of reports of Blown-up muzzel breaks due to the patches shredding inside the break. This is unfortunate as a soft lead bullet at 2000 fps is a devastating thing. I shot Baboons with a 470NE with cast PP bullets in Botswana and you could not believe the damage they did!
I am using both the 650gr, .577 NE Woodleighs and the 750gr. Bullets in my Nyati.But it's a tight fit. I have no more than .001-.002 cartridge to chamber clearance. Some of my bench guns are not this tight.
Since you have not had your rifle built yet, let me suggest that you have a custom reamer built with a .612 straight neck rather than the standard with a .608-.609 tapered neck. I think this would solve the brass problem and not cause case splitting if you anneal first. I am still having serious case fitting problems with my chamber. Perhaps if I were a worse gunsmith I would have produced a larger chamber, unfortunately, mine is really close to the reamer dimensions. The cases may be OK when they have been fireformed and when I reload them my problems may go away,however at the minimum you may need a taper crimp die to straighten out the case bulging at the neck/shoulder junction which prevents chambering. This is a similar problem to that encountered with .470 NE cartridges. The brass is so soft the bullet bulges it out on bullet seating regardless of the expanding method used.-Rob

OK, so I am not the only one who thinks the Bertram 585 brass is soft as dog turds.

Rob, in your 585's current chamber configuration, what would happen if you dropped a round in the mud, quickly wiped the mud off on your pants leg and tried to chamber the cartridge? I am not being critical, but it sounds like the chamber is too tight for that sort of event which I have experienced all to often when hunting.

I will have to check my neck reamer, but I think it is .614 and works great. But accuracy with my rifle is only 1 inch to 1.75 inches at 100 yards with a Leupold 2.5 power scope.

500 grains- IMHO this chamber is basically a benchrest chamber at this point and not suitable for a rough-use hunting rifle. OH it shoots great, and can be dealt with, but it's far from optimal! I totally agree with you on that perspective and yes I agree that a larger neck on this cartridge is absolutely necessary. Bertram brass is not only soft, but non-uniform in thickness.
Unfortunately, the Nyati shoulder is only about .040 wider in diameter than the neck which isn't much from the headspace perspective. Opening up the neck to .613-.614 corrects the brass fitting problem, but gives me some concerns about the reliability of maintaining the headspace particularily in the light of brass this soft as well as increasing the potential for split necks. I'd sure as heck not want to have a case separation in a full power Nyati load. I'm sure this is why they standardized on the .609 neck in the first place ( of course you really wonder if these guy really knew what they were doing). Nevertheless, a reamer designed with a larger neck would be the best solution.
Do you still have your neck reamer?-Rob

Rob,

I still have it. If you want, I will check its exact dimension and report. Dave Manson made it for me, and I think he charged $80, just FYI. I do not have a chamber reamer because I bought a pac-nor pre-chambered barrel.

I'd love to borrow it for a weekend or buy it if your interested. We can discuss by E-mail.-Rob

I talked to JGS and Kerri checked his reamer design records. The reamer dimensions came directly from Ross Seyfried! Remember, He had his brass made from .577 Bell NE and used the .590 rebated rim so it would fit in a modified M98 Mauser. I suspect this is the root cause of the problem.-Rob

Rob,

Everyone uses Seyfried's original dimensions, and everyone has ammo problems!

I will try to remember to dig the neck reamer out tonight. You are welcome to borrow it.

By the way, I ordered an 1150 grain .587 mold from NEI. Now we'll see how those Talley bases and rings hold up.

[This message has been edited by 500grains (edited 03-28-2002).]

take the brake off and let us know how she feels then

Robgunbuilder,

Mine too is built on a CZ550 action. It looks like you might be able to get #3 in the magazine with some work. Let me know if you figure it out. I think mine is a little under 12 lbs.

I am no gunsmith, and therefore cannot converse about some of these issues with the same level of accuracy, but it appears I have had similar problems with my cases and chamber fitting.

This is one of the toughest cartridges to reload--scratch that, it is the toughest to reload for. That little shoulder is hard to form and keep within tolerances once a big bullet is seated. I think there is some extra play in my reloading press, but not sure.

Another issue for mine is pressure. It does not appear I will be able to get anywhere near upper end loads with this gun. 140 grains of IMR 4350 and I?m showing serious pressure signs, not to mention considerable recoil (even with brake and 25? tube).

I have deceided that their are only two options:
1. Open the neck to .613-.614 with a neck reamer. This is the easiest solution but will effect accuracy negatively.
2. Form cases, anneal, fireform in the chamber with a squib load and either inside ream in the lathe or outside turn on a .585 mandrel.
The brass wall thickness is .0125-.0135, therefore, in theory a concentric case should be possible to manufacture by removing only about .001-.002. Unfortunately, the bertram brass is not uniform and to date I've destroyed 4 cases out of 9 getting this to feed properly with the right clearance.

I strongly suspect that your high pressure signs are due to insufficient case neck clearance. You really need .002 at a minimum. This is the classic problem of benchrest rifles with fitted necks. It's an incredibly DANGEROUS problem with a gun of the power level of a NYATI.
I've talked to JGS and they agree with me that the proper case neck dimension for this cartridge would be a taper from.613 ( mouth to .614 Neck/Shoulder juncture). This would make this cartridge much easier to load for and solve the problems described above.
I also talked to friends at Huntingtons and they said that if there was enough interest that they could talk Horneber into making 585 NYATI brass. If others out there want some E-Mail me.-Rob

I also asked Huntgington about some of that Horneberg brass in 585 and they said no. I would be interested.

Oh yeah, Rob I am going to the P.O. to mail your box in about an hour.

500 grains- Thank you very much! I appreciate your willingness to share this tool with me. Let me know the cost, I'll re-imburse you!-Rob

I and my mate would also be keen for some better .585 brass.

Regards PC.

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Mitch,
These guys are giving me a headache!
Thanks for letting me fire 43 rounds through your 577 Tyrranosaur. After the headache from that cleared up, I was able to rationalize my lack of need for a rifle throwing .585 caliber bullets.

.510 caliber is more than enough, and oh so much easier to live with in every way.

When the Atkinson bursitis sets in I will probably be limited to .475 caliber anyway, so I might as well get used to avoiding the .585's now, IMHO.

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RAB

Count me in on any new brass too.

I'm going to talk to Huntingtons and see what a minimum order would be. Then if enough of us are interested, I think we can get it done.I'll post when I have more info.-Rob

Heck, even I'd be interested in 10-30pcs of Horneberg brass in 585 Nyati if you can get some. I always need a reason for a future 'project' ;-)

(I can hear the UltraMag action from Olyarms calling my name)