A COW fire forming update. This should probably go into a new Thread, but I already posted a Thread covering my process. Oh well...
I just finished Cream of Wheat (COW) fire forming 20 RWS 8x68S cases and one Norma 8x68S casing. I employed the same lubricating oil (magical friction reduction) in a clean chamber before fire forming, and to the exterior of each the 21 cases, from the case head/web, all the way to the end of the case neck. I carefully measured and recorded each case length prior to, and after, fire forming.
Here's the skinny on the measured reduction in cartridge length, expressed in thousandths of an inch.
0.014" - Maximum measured on 1 case
0.013" - 2 cases
0.012" - 6 cases
0.011" - 1 case
So 10 of the 21 cases lost between 0.011" to 0.014" when COW fire formed.
All of the other 11 cases loss less than 0.011". Most of the other 11 cartridges
measured loss between 0.004 to 0.008" case length. The cartridge with the least reduction in length lost only 0.002" in length.
I think the Norma 8x68S cases contract less than the RWS cases, because the prior batch of cases I COW fire formed were all Norma cases, and their loss of case length ran only about 1/2 of the loss with the RWS cases today. And the only Norma case COW fire formed today lost 0.003" in case length. Only one of the 20 RWS cases gave up such little case length, at ~0.0025".
IMO, the Norma brass is softer throughout at least the body to neck length, because the bolt lift on the single Norma case today was notably stiffer than any of the 20 RWS cases. And that explains the lesser loss of case length. The Norma brass has a lower yield limit, and stretches forward more permanently, and with less spring-back after the pressure subsides.
I just finished Cream of Wheat (COW) fire forming 20 RWS 8x68S cases and one Norma 8x68S casing. I employed the same lubricating oil (magical friction reduction) in a clean chamber before fire forming, and to the exterior of each the 21 cases, from the case head/web, all the way to the end of the case neck. I carefully measured and recorded each case length prior to, and after, fire forming.
Here's the skinny on the measured reduction in cartridge length, expressed in thousandths of an inch.
0.014" - Maximum measured on 1 case
0.013" - 2 cases
0.012" - 6 cases
0.011" - 1 case
So 10 of the 21 cases lost between 0.011" to 0.014" when COW fire formed.
All of the other 11 cases loss less than 0.011". Most of the other 11 cartridges
measured loss between 0.004 to 0.008" case length. The cartridge with the least reduction in length lost only 0.002" in length.
I think the Norma 8x68S cases contract less than the RWS cases, because the prior batch of cases I COW fire formed were all Norma cases, and their loss of case length ran only about 1/2 of the loss with the RWS cases today. And the only Norma case COW fire formed today lost 0.003" in case length. Only one of the 20 RWS cases gave up such little case length, at ~0.0025".
IMO, the Norma brass is softer throughout at least the body to neck length, because the bolt lift on the single Norma case today was notably stiffer than any of the 20 RWS cases. And that explains the lesser loss of case length. The Norma brass has a lower yield limit, and stretches forward more permanently, and with less spring-back after the pressure subsides.
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