Norc M 14
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Get the headspace measured ...
check the stickies in the battle rifle section for some theoretical advice.
If you want to see for yourself what exactly the reality is, cut a cartridge in half legthwise,.
See if there is a thinner "stretch ring" inside the brass.
check the stickies in the battle rifle section for some theoretical advice.
If you want to see for yourself what exactly the reality is, cut a cartridge in half legthwise,.
See if there is a thinner "stretch ring" inside the brass.
Could be an excess headspace situation. If your rifle has the generous tolerances sometimes seen, and you are FL sizing, the case is going to get stretched, and could fail. If you section the head area of some of your fired cases as suggested you may see the internal groove indicating incipient separation. A solution could be to size cases to suit your rifle. Keep in mind that cartridges must chamber freely without hesitation.
maple_leaf_eh
CGN Ultra frequent flyer
Breaks? Splits? Separates?
If the ejected empty looks like a .44 Magnum casing (.308 Win sized base and straight sides), it sounds like a separated casing. Don't go gouging at the broken ring with a screwdriver! Get a separated casing tool. Use the correct tool correctly. The cause would be loose headspacing, or at least that was what we were taught on a machine gunner's course once upon a time.
Tiriaq showed me a nice rebarreled Garand that some Jacka$$ had used a flat-blade screwdriver trying to clear the chamber. All he did was gouge and scrape the chamber really baddly.
How many times have you reloaded that particular piece of brass?
I was pretty interested in Norinco headspace earlier this spring/summer; in exploring this interest I wound up measuring about a dozen different M305s with their factory bolts and discovered that they all measured quite long, averaging approximately 1.644 (which just happens to be pretty close to NATO 7.62 field reject). SAAMI .308 GO spec is 1.630, so most full length resizing dies are going to size your brass to something slightly less than this. Then when you fire that round in your rifle with it's factory bolt (ie: long headspace), the brass stretches from around 1.629 all the way out to 1.644. Then when re-loading you work it back down to 1.629 only for the case to be re-stretched back out to 1.644 again when fired. Several cycles with this degree of stretching back and forth and it's not surprising your brass might separate.
While adjusting your die to resize the case closer to whatever the headspace is in your particular bolt/rifle combination will likely get you much better brass life, you'll also want to be careful in doing so. The reason for this is that if you size your brass right on with whatever your headspace is, you increase your potential exposure to either a slam-fire or an out-of-battery detonation. This might happen if tightly sized brass winds up piling up against a bit of dirt in the chamber, preventing the bolt from rotating completely into battery. Theoretically the firing pin bridge in the M14's receiver would prevent the pin from moving forward when struck by the hammer, however I've seen plenty of chipped/broken firing pin tangs and one receiver who's bridge was out of spec and not working right. All in all a pretty low probability of all these things stacking up against you to create the ka-boom, however it has definately happened to some in the past so something at least to be aware of. Most M14 armorers I have talked to suggest resizing with about a 2 thou safety tolerance. Some also recommend you don't reload the same piece of brass more than 4 times.
Good luck!
Brobee
I was pretty interested in Norinco headspace earlier this spring/summer; in exploring this interest I wound up measuring about a dozen different M305s with their factory bolts and discovered that they all measured quite long, averaging approximately 1.644 (which just happens to be pretty close to NATO 7.62 field reject). SAAMI .308 GO spec is 1.630, so most full length resizing dies are going to size your brass to something slightly less than this. Then when you fire that round in your rifle with it's factory bolt (ie: long headspace), the brass stretches from around 1.629 all the way out to 1.644. Then when re-loading you work it back down to 1.629 only for the case to be re-stretched back out to 1.644 again when fired. Several cycles with this degree of stretching back and forth and it's not surprising your brass might separate.
While adjusting your die to resize the case closer to whatever the headspace is in your particular bolt/rifle combination will likely get you much better brass life, you'll also want to be careful in doing so. The reason for this is that if you size your brass right on with whatever your headspace is, you increase your potential exposure to either a slam-fire or an out-of-battery detonation. This might happen if tightly sized brass winds up piling up against a bit of dirt in the chamber, preventing the bolt from rotating completely into battery. Theoretically the firing pin bridge in the M14's receiver would prevent the pin from moving forward when struck by the hammer, however I've seen plenty of chipped/broken firing pin tangs and one receiver who's bridge was out of spec and not working right. All in all a pretty low probability of all these things stacking up against you to create the ka-boom, however it has definately happened to some in the past so something at least to be aware of. Most M14 armorers I have talked to suggest resizing with about a 2 thou safety tolerance. Some also recommend you don't reload the same piece of brass more than 4 times.
Good luck!
Brobee
