I am getting real close to finishing my new Ground Squirrel gun. However I've run into a major problem. The 585 Bertram brass I use has an inside taper which causes a loaded round to bulge near the neck/shoulder and exceed the chamber dimensions. The chamber has a .6095 neck and the loaded rounds ( dummy round only at this stage) at the bulge are .612. The Brass is also quite non- uniform with case wall thickness varying from .012 to .014.
Outside neck turning just corrects the problem, but I am concerned about the required reduction in wall thickness to allow for a .003 inch neck clearance for safety.
I believe the right answer is to inside neck turn the sized cases, removing about .002 inches and producing a straight neck, then seating the bullets. Since inside neck turning dies for this caliber are a custom item only ( 5 month wait from RCBS), this probably can only be done in the Lathe. I think a custom chucking reamer is the best solution!
I believe 500 grains and Todd E have modified ( increased the neck dimension) of their rifles chamber to avoid this problem, however, given the near absense of a shoulder to headspace on in the Nyati, I am very reluctant to pursue this approach.
I wonder if anyone else has a better solution?-Rob

I have had the same problems.
I solved them by fireforming the cases.
Insted of using a bullet I load the first cartridge with soap. I fill the case with powder and press the case through a piece of soap. May sound silly but it works.
The soap gives enough pressure so that the case is formed properly.
Then I load it with a bullet and everythings ok:-)

Rune- I don't doubt your solution to the problem, but I don't understand why fireforming would correct a tapered neck given that the neck dimensions of the 585 Nyati are also tapered slightly-.608 at the case mouth to .609 at the shoulder. Of course if it works I'd love the solution to be so simple. Are you using Bertram brass and who's dies are you using. I'm using RCBS dies and they claim .610 neck diameter in the seating die,Which isn't helping matters.-Rob

I also use Bertram brass and RCBS dies.
I discovered that when I ran the case through the form die the neck is way to tight for the bullet to be seated properly. As a result the shoulder collapsed when I tried to seat the bullet or the case was bulging right above the shoulder and would not fit the chamber. When fireforming the cases first these problems were eliminated. I have tried only one lot of cases. I guess the dimensions can vary from lot to lot with the Bertram.
So far it has worked very well for me.

You are correct my rifle has a loose neck. This poses issues with resizing in that I get alot of spring back and loose fitting bullets. I gave up after returning the sizing dies twice I gave up and just made my own neck sizer die.
You must be running a pretty tight neck. With the given parameters I think that your original idea (ID turning the brass) is the best. My Bertram cases measure .013 to .015 thick at the neck by the way. So the variation is not limited to 585 brass.

Todd E

Guys- Thanks for the info. Here is what I've found. At the case mouth my sized brass is .594 O.D. and .572 I.D. Thus the brass at mouth is approx. .011 thick. At the shoulder the brass is .596 O.D. and .564 I.D. Thus it's .016 thick at this point or tapers .005 inches. To properly correct this I think I will first try a .570 chucking reamer straight to the shoulder. This should resolve the problem. I will also try Rune's much simpler approach, although I still don't understand why it works.-Rob

Here you go Rob, just think Benchrest, the guys use tight necks (I have a good number of reamers that have necks smaller than a standard loaded cartridge) and outside neck turn. Why outside neck turn instead of inside neck reaming? If done properly, it is more accurate. The objective in outside neck turning is to have consistent neck wall thickness. But, when outside neck turning, the neck diameter of a loaded round is much smaller than the chamber neck and the bullet does not get a concentric start in the bore. So, most benchrest chambers are set up to be about 0.0015" to 0.002" larger than the turned neck. ( I have used as little as 0.001", but this requires extreme care in loading rounds, easy to get pressure spikes) You want a good bit more in a DGR.

So, here is how to accurately outside neck turn your .585 brass without expensive equipment, provided you have a lathe, which you do:

Resize cases. Inside chamfer the mouth.

Chuck up a piece of round bar stock in the lathe.

Turn the diameter to bullet diameter, with a step at neck length. Chamfer the end. don't take it out of the lathe!!!! This is your mandrel.

Take a cartridge case, and with a ball bearing center in the tailstock, and the center point in the primer pocket, push the case on the mandrel by turning the tailstock handwheel until the neck stops at the shoulder. Leave the center in the primer pocket.

Turn to proper O.D. for chamber clearance. Don't go into the shoulder. It is easier to run the tool bit to the right, towards the Tailstock (feed in reverse). If the lathe crossfeed holds zero well, once you turn the first case, the remainder will be easy. I grind a special tool for this with a non cutting right edge the same angle as the shoulder, and a small cutting edge on the tip.

To pull the case off the mandrel, take a shell holder. Anneal it if it is hardened. Drill and tap through the primer punch hole for about a 3/8-24. Take a 3/8-24 bolt about 2 inches long, cut off the head. Chuck this headless bolt in the tailstock drill chuck. Slip the shellholder over the case, bring up the tailstock chuck, and thread the shell holder onto the rod while extending the ram. Lock down the tailstock and back off the handwheel. Be sure the tailstock chuck tapered shank is tight in the ram.

A lot of words above, but once you get set up it is easy & fast.

Everytime you start this operation, begin with a fresh piece of round bar stock and turn to bullet diameter. By doing this, and leaving it in the lathe, the neck wall thickness will be constant around the circumference.

After you fire the cartridge, the step in the outside of the neck, from turning, will go away (actually it is now on the inside, this is why you must turn the entire neck).
This little inside buldge in the neck is called "The Dreaded Donut". If the bullet enters the donut when reloading the case, then we will be back at a tight neck, and overpressure, situation.

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[This message has been edited by John Ricks (edited 03-14-2002).]

[This message has been edited by John Ricks (edited 03-14-2002).]

Rob, actually the method I described is easier than using a chucking reamer, as the brass will spring away from the chucking reamer. The beauty of the mandrel turning is the neck is the same OD as it would be with a bullet seated. Just measure the OD with a mike while turning until it is where you want it for clearance.

[This message has been edited by John Ricks (edited 03-14-2002).]

John- You have saved the day! I was just going to take the sizing die and remove the decapping pin, Run the case into the sizing die and stick the whole assembly in a collet chuck with a stop pin against the case head and inside ream with a .570 chucking reamer. This assumes that I can get a proper minimal runout on the sizing die body. I was prepared to zero this on the lathe. I was hoping that the compression fit into the sizing die would be sufficient to keep the case from turning and springing away from the reamer during the reaming cut. Nevertheless, you are absolutely correct and I will do as directed and follow your procedure. I knew there had to be a better way! It's great to have so many really knowledgeable people around on this web-site who are willing to help when you have a problem. Thanks-Rob

Going from memory, the dimension of a 585 nyati round (bullet seated) at the case mouth should be .605, but mine were running .618 or .620, or something like that. There was no bulge, but they would not go into the chamber - no way. I bought a custom made neck turner, but I was worried about the ability of thin necks on soft brass to hold big bullets in place during HEAVY recoil. So instead I had a chamber neck reamer made and reamed out the chamber. I don't remember the dimension but I could check.

Even after neck reaming the chamber, there is plenty of shoulder for headspacing both before and after fireforming. The 585 nyati has much more shoulder than the .400 Whelen or other questionable cartridges.

Since these Bertram cases have so much internal taper,I have to agree that the best way to remove it is to creat a .577 diameter straight hole using the bullet diameter mandrel that John Ricks described, then turning the case to provide adequate clearance in the neck. That taper just has to come out one way or the other or you live with bulged cases. The procedure John described in effect moves the taper from the inside of the brass to the outside where it can be turned off in the Lathe. If done carefully, this should not result in case walls less than .012 thick straight to the shoulder which will result in loaded rounds whose diameter should not exceed .601.I think this much brass in the walls should not result in any set-back even under heavy recoil. Since the brass will spring a little bit, my guess is they will wind up about .603( maybe a bit more) or so which will fit my chamber with lots of clearance. From my cerrosafe cast, my neck at the mouth is .608 and at the shoulder .609 which is in excellent agreement with the Reamer specs I got from JGS. These cartridges should just drop in!
500 grains and Todd E - I appreciate why you chose to open the necks on your guns, however, In my view there just has to be a better way.Nevertheless, its fun to solve these problems in different ways isn't it.-Rob

Just finished turning some 585 Nyati cases on the Lathe. I followed John Ricks procedure and they came out beautiful and feed flawlessly. I made a .585 mandrel on the Lathe from some bar stock and using a live center slowly ran the case onto the mandrel. It sure didn't look good. Big Bulges near the shoulder from the inside taper that now had moved outside. Took some slow feed light cuts and was able to turn the case down to .608 all the way from the mouth to the shoulder. Bullets fit fine, crimp properly and look good.getting the case off the mandrel also worked fine with a threaded shell holder in the tailstock. Thanks John that was a great solution.-Rob

I suppose another solution to the 585 brass problem would be for a more competent brass maker to pick up the cartridge.

But that is probably wishful thinking.

500,
A few days ago I dumped 40 Bertram .505 Gibbs cases in the garbage. The variation in rim thickness was well beyond belief. I went through 3 extractors and could not achieve a profile that provided suitable reliability.
Upon receiving the new "HDS-H" cases from Huntingtons, all 3 of these extractors operated flawlessly.

Would it be possible to petition a better brass maker to pick up the cartridge??

We could all e-mail them, probably wont get us anywere but you never know.

I made the mistake of buying .416 rigby brass in Bertram and it is pretty shit really compared to the handfull of norma cases I have. Runs through my dies like play-dough.

I will be forced to use it when my .585 is finished.

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