458 Case Separation

23 May 2002, 10:40

Nitro Express

458 Case Separation

Just came back from the range where I had a bad experience with reloads in my 458 Win Mag.

I have been loading 62.3 grains of H4198 Extreme, which produces about 2070 fps with a 500-grain Woodleigh Weldcore. I've shot probably 300 rounds of that load with no problems.

Today I had a complete separation of the case, just ahead of the belt. The remainder of the case is stuck in the chamber, and the gunsmith who owns the range is getting it out for me.

The recoil was not any different than usual, and the point of impact was exactly the same as my other shots.

Temperature outside was moderate and I had shot four rounds earlier, then put the rifle aside for about 10 minutes.

The case was a Winchester which had been fired once before. Primer was a Federal 215.

Rifle had not been cleaned immediately before going out today but had no more than 10 rounds through it since the last thorough cleaning.

The firearm is a Steyr Model S that I've had for several years, with no previous problem. I did have a partial separation a year or so ago--I think that case had been reloaded several times, and it split about halfway around at the same place, but did not completely separate.

Any thoughts or theories, or was this just a random occurence?

23 May 2002, 11:18

Robgunbuilder

Check your headspace. It sounds like its marginal. I'd take a sharp wire bend a short 90 degree angle in it and feel around inside some of your other fired cases for evidence of a fissure or ring which would indicate partial insipient head speparations are occuring. A belted magnum that exibits head separations after only 1 reloading is not due to any random occurance and has got to be due to one of three things. Excessive headspace( most likely), really- really poor quality brass or a major overload. What did your primer look like compared to a factory round ;was it excessively flattened? You should mike the belt and see if it expanded beyond .003. If so you had a major overload. Whatever you do, don't shoot this thing again till you define the problem and fix it.-Rob

23 May 2002, 12:27

Nitro Express

Robgunbuilder:

I'll check the inside of some cases.

I know it was not an overload, as I weigh every charge with this particular caliber. Couldn't be a double charge as the case would overflow.

Primer looks fine. There is a round extractor indention on the rim.

Brass is Winchester, bought new and fired once.

Headspace might be the answer. Thanks.

23 May 2002, 13:05

John Ricks

As Rob mentioned, this is the classic example of too much headspace on the belt. When the cartridge is fired, the case walls are held to the chamber by the pressure, and the belted head is pushed to the rear until it makes contact with the bolt face. After a firing or two, the walls of the case just ahead of the belt are stretched thin enough to separate. Cure is to set back the barrel a turn and rechamber, paying attention to how far one runs the reamer in!!!!!!

You may be able to have a makeshift remedy by measuring belt thickness on various makes of brass and select accordingly. I have seen as low as 0.208" and as high as 0.217". The Go Gauge is 0.220".

A note, for DGR reasons, factory rifles are chambered to accept any and all brass belt thickness. I have seen new factory rifles that would acept a No Go Gauge. I chamber a DGR so the bolt will just close on a Go Gauge, as I never know what ammo the hunter will use. Different story for a match rifle.

If anyone has a pet server for posting photos, let me know and I will post a photo of a special gauge I made that accurately measures belt thickness. Handy for sorting brass.

(I have not tried huntingpictures.com since they crashed)

And there is a quick way to measure just how much excessive headspace one has in a chamber by using a dial indicator and a new unfired case. Again, I will post a photo if a server is available.
------------------
Currently in Exile on the Beautiful Olympic Peninsula of Washington State.

Email Address is rifles@earthlink.net

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[This message has been edited by John Ricks (edited 05-23-2002).]

23 May 2002, 14:05

Robgunbuilder

I agree with everything Rohn Ricks says-as usual! However, you mentioned a ejector mark on the case rim. Is this bright in appearance and pronounced? If so,this is a classic sign of excessive pressure. Check your belt diameter. I suspect you have a combo of slightly high pressure,marginal brass and marginally excessive headspace and this is causing the head separations. Like john said, it's a simple barrel set-back fix.
John- I'd love to see those pictures. Perhaps you could send them to me by E-mail. In return, I'm machining a .50 BMG receiver right now and have some great pictures you would appreciate.-Rob

24 May 2002, 13:09

Nitro Express

Well, I had the headspace checked today, and it is just exactly where it should be.

Therefore, I can only conclude that I happened on a bad case, or maybe a bad batch of Winchester cases.

I KNOW the load was OK, and I've fired factory loads with greater velocities than my handloads, with no problem.

Any other ideas?

24 May 2002, 13:37

D Humbarger

Nitro you just got the best advice available on this board. Use all of it.

------------------
Doug Humbarger
NRA Life member

24 May 2002, 14:42

<Don Martin29>

Nitro,

What do you find with the wire feeler gage? You and all handloaders of belted magnum cases should use one. With cartridges like the .458 and .300 H&H in particular.

Does that Styer have rear locking lugs? If it does like my 99 Savages then the cases will weaken even if it's a rimless case!

Of course the severity of this will be greater the hotter the load.

The cartridge belt tolerance is .220 -.008" and the chamber dimensions is .220"-227". So this is just where the problem starts. Then many primer pockets are very tight and even shallow so the primer may not be that flush. Thus the primer holds the case against forward in the chamber and upon firing the case head goes back and takes some metal with it from the web.

So get a "Whitetail" primer pocket reamer and use it.

I checked my headspace by puting some soft solder on the belt and closing the bolt on the empty case. Both of my M-70's in .300 and .375 H&H measured .228" to the deformed solder. Neither rifle has been fired much.

So case life with some belted mags may be only 5 shots or so many only one shot with rear locking lugs.

These belted cases were never designed to be reloaded. It's too bad that the great cartridge designer Charles Newton did not have better business sucesss. Instead we got Weatherby who did not know. Finally 80 years after the .30 and .35 Newton we have the Jeffery case being used.

None of the great designers used belted cases. Not Kalishnakov, Browning, Springfield, Garand nor Mauser. Nary a belt.

But with factory loads you don't have much concern. Rifles with rear lugs have a shorter stroke so thats a advantage there.

24 May 2002, 15:15

Pecos41

quote:
Originally posted by Don Martin29:
Nitro,
Case life with some belted mags may be only 5 shots or so many only one shot with rear locking lugs.
These belted cases were never designed to be reloaded. It's too bad that the great cartridge designer Charles Newton did not have better business sucesss. Instead we got Weatherby who did not know. Finally 80 years after the .30 and .35 Newton we have the Jeffery case being used.
None of the great designers used belted cases. Not Kalishnakov, Browning, Springfield, Garand nor Mauser. Nary a belt.

I think you really hit the nail on the head with your comments, Don. I have never found belted cases to have very good case life. Whereas with many non-belted cases I have reloaded them without problem so many times it would frighten me to know. For example, the 30/06 case. Sometimes I think the only way to kill this case is with a sledge hammer on an anvil. Good post.
(Not that many magnum shooters will listen to it.)

25 May 2002, 09:10

9point3

You guys are right about belted cases but there aint really no other way to get the 458mag to headspace unless you want to try the mouth.

27 May 2002, 16:04

Bbear

don't forget the 256 Newton. Still one of my fav's.

As for the belted cases, I think think they've hit the nail on the head. They aren't really designed for much reloading.

28 May 2002, 09:27

Andre Mertens

Nitro, all reply elements are condensed in the above posts. Headspace is the culprit and is further compounded by your rear locking Steyr. This kind of lockup is bound to be more elastic than front locking lugs. You better monitor your cases after each firing in order to anticipate incipient case separation (the "hook" does the trick). You will also have to accept much reduced case life. Years ago, I owned a Steyr-Mannlicher Luxus Stï¿½tzen in 7x64 that behaved the same way, even with partial sizing and the much more pronounced shoulder of that ctg notwithstanding. Still, I had to retire cases after 2-3 firings when they started to develop a grooved inside, just above the casehead.