Warrior, Have you had any Winchesters or Remington cases brake just above the belt on the 300 H&H? My hunting parnter has a Winchester Pre64 model 70 300 H&H that has broken them just above the belt on older cases. Then the case is still in the chamber.Luckily it was at the range. So I have decided to get new cases for hunting and just use the older cases for range work. Rather have a case head separation at the range then in a hunting situation.

I have never used Remington cases at all in my 300 H&H, as at the time I could only get Winchester cases. Also, I have not had my Winchester cases giving case-head separations as I work carefully with them - I have tossed some of them even before using them, but that was based on other criteria. Also, I have never used old cases that were suspect or corroded. I cannot comment on the quality of the cases that's giving you this problem that breaks off just ahead of the belt, but my advice is toss them, and do not kid yourself that they are OK on the range - it is equally dangerous on the bench as in the hunting field. It may not only wreck your rifle, but also hurt you severely. It sounds as if you are experiencing classical case-head separation.

However some other points should be made or considered as some background:

Headspace:

The main culprit is when one has a headspace problem - either in the rifle itself or induced by pushing the shoulder of the case too far back. With the 300 H&H though, that headspaces on the belt, the brass gets worked more than those cartridges that headspace on the middle of the shoulder, affording less play. Also, firing and full-length sizing cold-works the brass more than just neck-sizing, and so it is making the brass more brittle. These are just the basics that we have to accept as being normal. I let my 300 H&H cases headspace on the shoulder and not the belt, and so extend the case life. It is suggested to anneal your cases in a factory chamber after 5 firings as a precaution.

Chamber:

Get your chamber dimensions checked to know whether they are in spec. Some chambers are cut oval and not completely concentric - needless to say this condition is bad and cannot be rectified, other than to have the chamber re-cut or the barrel replaced. Chambers need to be cut within a certain tolerance spec - between min & max. It stands to reason that 'loose' chambers cold-work brass more than 'tight' chambers, and that is why match rifles give much better case life than mass-produced factory rifles. Often we see that the neck does not expand fully, and so soot is thrown onto the shoulder, but bear in mind that a down-load round can do the same, as the pressure is not high enough.

Brass:

Worst of all are the use of brittle brass in high-pressure cartridges that are hot-loaded. Even brand new brass can be brittle, although rare, but may refer to specific lot. Luckily I have not encountered it personally. Brass is susceptible to stress corrosion cracking, especially from ammonia or substances containing or releasing ammonia. Lightly coloured brass may indicate the onset of corrosion and can still be cleaned and used, but once it turns to a crusty green and/or has black spots under it, the zinc has been leached out of the brass, and rendering it suspect. Such corroded cases should be tossed immediately; it is not worth the risk. The blue-green color of the corrosion is copper sulfate and the whitish residues are some salt off the zinc. The red areas of the cleaned brass show that the zinc content has been removed to show the reddish copper. The shelf life of modern ammunition (both commercial and good handloads) is virtually indefinite if kept under ideal conditions — sealed, cool and dry.

Water damaged surplus ammo is another danger for those that like to shoot military ball ammo. Any ammo that was wetted for a period of time is a no-no in my books. I have seen wetted ammo, packed in carton boxes that were stored in a solder for a long time. Do not shoot them if donated to you. Military ammo generally has the primers sealed with varnish, but I still do not trust it when kept damp for a long time. Non military ammo that got wet is more susceptible to deactivate the primer compound or give a delayed reaction before going off, or worse yet, going off whilst you open the bolt to eject the misfire.

Your brass must be managed. Log the number of times that you use a given lot of cases, and don't get them mixed up so you can no longer remember how many times you have shot them. I normally load in lots of 20 rounds at a time, but never more than 50, if the need is there. I never use other people's brass or pick brass up at the range, I only use new brass fired in my own rifle, so I have control.

Case necks:

Case necks can split and do split when they become work-hardened and so losing their elasticity, whereby they do not 'spring back' anymore. That is why cases need annealing after a certain amount of usage. Annealing is nothing more than heat-treating a portion of the case and letting it cool. Only the neck, shoulder, and upper body can be safely annealed at all. The rest of the case must retain its original hardness. The head cannot be safely softened, and should never be annealed. Over-annealing is also a problem. The neck is quite easy to over anneal - get it too hot, which makes it too soft, and it's too weak again to grip the bullet as tightly as it should.

Action and extractor:

The cartridge case is the weakest link in the chain, but due to strong actions most of the time we do not often see disasters where the individual gets hurt, but given the right conditions it will not resist a burst case and will rip the extractor off, or worse, peal the sides of the action away. Remington bolts have been fitted with frail extractors, and it is common amongst benchrest shooters to replace them with Sako extractors, as they load to higher pressures. We have seen on various gun forums that even strong actions, made from modern steel, like the Sako 75, has been destroyed.

Case inspection:

Typically astute reloaders will pay a lot of attention to case inspection - checking the necks for cracks, inspecting for insipient case-head failure, flattening of primers, seating primers too easily or expansion of primer pockets, formation of doughnuts at the junction of the neck and shoulder. Don't be shy to toss cases when in doubt. I never bother with sub standard stuff and will not even try to recover corroded brass, as the pictures that I have seen have totally scared me off.

Warrior

Here is a new way to measure a fired cartridge case for the correct head spacing in YOUR chamber, and then you set your die accordingly.

http://www.larrywillis.com/instructions2.html

Warrior

Thanks for the information Warrior. It has not happened in my Remington 721 but has in my partners Winchester Pre 64. Sound like I we should be neck sizing only and really inspect the casings. The older casing has the discoloration to them. Sounds like we need to give them a toss in the trash can.

700xcr,

The first early warning of likely case failure is when you see that bright ring just ahead of the web or belt at the case head. This is where the case stretches due to either excessive headspace or the case shoulder being pushed back too far, which can be corrected by setting your sizing die correctly. When the case shoulder has been pushed back too far, the case will stretch on firing to match the headspace available in the gun and so fill the chamber.

And this is where a device can be of great assistance. Most people worry about the jump of the bullet to the lands more in terms of accuracy, when in fact most reloaders overlook this aspect that would lengthen our cartridge case life. The bright ring that I refer to is pretty recognizable in that it has a crystalline appearance and is likely to be about 1/8" or so wide. Do not confuse this with the abrupt ring that appears at the same juncture when a relatively sloppy chamber is encountered.

One can check to see if incipient case head separation has occurred by using a bent paper clip to feel inside the case for a groove on the inside of the case, opposite the bright line. If present, an abrupt, easy to feel ridge will be felt. If so, these cases must not be used again, and offered to a gun shop or scrap metal dealers - do not throw them in the dustbin.

http://bulletin.accurateshoote...ow-to-spot-problems/

Warrior