Overloading the Powder

[Blr243]

Here’s a pic headspace vastly different between the two

[Blr243]

When a 222 Sits against the bolt face in a223 chamber there is enough room at the front of the chamber for a fox to have a fight with a rabbit

[JimTom]

Rimless cartridges headspace is measured from the shoulder. Headspace vastly different with the two cartridges.

[marksman]

I thought headspace was the gap between the bolt face and breech?

the case headspaces off the shoulder and the bolt face as Blr has said so the case could slide up the chamber from the firing pin hit till the bullet hits the lands stopping it so there is enough force to set off the primer that would then go off so the case was headspaced off the bullet and bolt face before the case gripped the chamber, BOOM, to much headspace, the shoulder of a 222 is not as far up as the 223

when l am forming cases from one shape to another l have to create a false shoulder or jam the bullet eg... when making 17 ackley l take the case from 22cal to 20 cal then bring the neck down at 17 cal so l can just close the bolt with a case in the chamber, the case is head spaced off the false shoulder
when l am making 6mm dasher l can just do a 6mm br load and jam the bullet or create a false shoulder by expanding the neck to 7mm then bring the neck back down to 6mm so l can just close the bolt on a round, there needs to be something to hold the different shaped case back till the case expands and grips the chamber

l have seen the exact same thing happen when someone shoots a 308 in a 30-06

[Blr243]

So when the disaster happens and the case does not grip the chamber walls , does gas, instead of going down the barrel, find its way back into the chamber ( between the case and the chamber) and then start escaping and blowing mags out and all that sort of shenanigans?

[Peter988]

So when the disaster happens and the case does not grip the chamber walls , does gas, instead of going down the barrel, find its way back into the chamber ( between the case and the chamber) and then start escaping and blowing mags out and all that sort of shenanigans?

Most definitely in my case. Thanks all for the explanation.

[Oldbloke]

And for that I mean for a case like my 243 that has a shoulder. A 45 acp headspace is measured from the case mouth back to the bolt face because it’s the case mouth that stops the case being chambered too deep. So I think people who crimp the mouths too much on their acp may be messing with their headspace a bit. Not sure. Have not loaded for pistol in over a decade For safety and for case life and for perhaps accuracy I like to size my cases in my 243 so that I can feel a slight compression as I close the bolt completely. Then I know it’s tight and there’s no slop slop. It just feels right to me

Yeh, that slop is head space for a rimless case.

For a rimmed case its the gap from the bolt to rim.

Bloody text. Often hard to explain.

[marksman]

when the primer blows a big gust of gas is forced wherever it can go, usually the easiest path
depending on the rifle to how much comes at your face/eyes some makes control it better than others but it is better to have it channelled away from your face and into the mag well, sometimes its bad enough to burst the timber around the mag and distort everything in that area

it can wreck triggers and on push feeds usually the ejector button will be knackered,
you can have indents on the case with a good amount of carbon soot down the case

this photo shows from the left 2 x 308 cases that were shot in a 30-06 chamber both were push feeds and the bolts were ruined, note the small indent on the middle case at where the shoulder should be
the case on the right is a 9.3 x 62mm shot in a 375 H&H chamber, it only shot because the rifle was a mauser 98 and the claw extractor held it in place, the primer did not blow and the bolt was not ruined, the m98 was able to keep shooting



this is what the primer pockets from the 308 cases look like

[Oldbloke]

Yeh, you hear about this sort of thing happening. And the more rifles you have more likely there is an ammo mix up. Was the shooter ok?

Also says something about rifle design

[Blr243]

Thanks MM AND OB

[TassieTiger]

So when the disaster happens and the case does not grip the chamber walls , does gas, instead of going down the barrel, find its way back into the chamber ( between the case and the chamber) and then start escaping and blowing mags out and all that sort of shenanigans?

Most definitely in my case. Thanks all for the explanation.

Don’t Most rifles have generally 3 x ports for blow back ?

[Blr243]

I have heard that sometimes or often there is some sort of safety porting system but don’t know a lot about it One of my fathers army mates told me that in Vietnam he found an enemy soldier dead in the bush from his own blown up rifle

[TassieTiger]

Like this one

[Oldbloke]

Yeh, usually halfway along the bolt directing down in to the mag. I think my M70 has one there.
Interestingly I just looked at the bolt in my Marlin XL.
It's just behind/under the locking lugs. A bit unusual.