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Shooting & Reloading - Mausers, Big Bores and others >> Rifles

mauserand9mm
.400 member

Reged: 03/09/09
Posts: 1040
Loc: Queensland, Australia

Re: My 35.303 is Finally Finished
15/02/11 08:57 AM

I didn't think stretching resulting in head separation was an issue with fireforming rimmed or belted cases, providing the headspace is correct. You definitely need to create a "defacto" headspace shoulder in rimless cases.

Normally the case will stretch because the firing pin will drive the entire case forward (minimal amount if the headspace is correct) and then the gas pressure holds the forward part of the case against the chamber and pushes the solid case head back against the boltface, stretching the brass just forward of the web (where the solid head becomes the start of the case wall ie the brass "thin" brass starts).

If the headspace is good on a belted or rimmed case, and the brass doesn't fill the chamber (ie as in fireforming from another cartridge) then the case will mainly blowout to fill the chamber. With tight headspace the case head will start and finish in the same place so there should be negligable stretching.

Rimless cases with small (ie weak) shoulders have to be checked for stretching, even with good headspace because the weak shoulder is set back by the force of the firing pin as it is forced into the front of the chamber - this effectively increases the headspace at the instant of firing. Two example cartridges that do this (from my limited experience) are the 8x57 and the 505 Gibbs. I have a couple of 8mms and the cases will either die from neck splits or incipent head separation, but I still get around 10 loads out of them. I know a guy with a 505Gibbs and, even though he has set his FLS die up for minimal resizing (to suit his rifle), he only gets 5 or 6 firings out of his cases and they all fail due to incipent head separation.

I never had head separation issues with strong shoulder cases eg 308, 30/06, 6.5x55, 270, 7x57.

I know some people that have had 303s with bad headspace and have used the shoulder for headspace, like in a rimless case, but the shoulder is still relatively weak and case life not good.

Edited by mauserand9mm (15/02/11 09:03 AM)

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Subject	Posted by	Posted on
My 35.303 is Finally Finished	Perry	31/01/11 11:23 PM
Re: My 35.303 is Finally Finished	mehulkamdar	05/02/11 03:23 AM
Re: My 35.303 is Finally Finished	Perry	14/02/11 07:11 AM
Re: My 35.303 is Finally Finished	Rule303	14/02/11 12:25 PM
Re: My 35.303 is Finally Finished	Perry	14/02/11 08:11 PM
Re: My 35.303 is Finally Finished	ovny	14/02/11 08:26 PM
Re: My 35.303 is Finally Finished	DarylS	15/02/11 03:16 AM
Re: My 35.303 is Finally Finished	mauserand9mm	15/02/11 08:57 AM
Re: My 35.303 is Finally Finished	DarylS	15/02/11 09:45 AM
Re: My 35.303 is Finally Finished	mauserand9mm	15/02/11 02:39 PM
Re: My 35.303 is Finally Finished	450_Ackley	15/02/11 05:25 PM
Re: My 35.303 is Finally Finished	Perry	15/02/11 10:17 PM
Re: My 35.303 is Finally Finished	DarylS	16/02/11 01:40 AM
Re: My 35.303 is Finally Finished	mauserand9mm	16/02/11 09:01 AM
Re: My 35.303 is Finally Finished	450_Ackley	16/02/11 03:51 PM
Re: My 35.303 is Finally Finished	mauserand9mm	16/02/11 05:11 PM
Re: My 35.303 is Finally Finished	DarylS	17/02/11 03:50 AM
Re: My 35.303 is Finally Finished	Rule303	20/02/11 07:35 PM
Re: My 35.303 is Finally Finished	mauserand9mm	17/02/11 08:44 AM
Re: My 35.303 is Finally Finished	NitroX	31/01/11 11:51 PM
Re: My 35.303 is Finally Finished	rigbymauser	01/02/11 04:03 AM
Re: My 35.303 is Finally Finished	Perry	01/02/11 06:49 AM
Re: My 35.303 is Finally Finished	Ben	01/02/11 07:04 AM
Re: My 35.303 is Finally Finished	458Shooter	02/02/11 07:22 AM
Re: My 35.303 is Finally Finished	Rule303	02/02/11 10:33 AM
Re: My 35.303 is Finally Finished	NitroX	02/02/11 03:20 PM
Re: My 35.303 is Finally Finished	DarylS	03/02/11 08:49 AM

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