Case weight?

[the big greasy]

Thanks everyone!, looks like I have some forming to do!

 

[Tripodmvr7]

Don't waste components on fire forming. It takes very little energy to blow out the case to fit the chamber. You might get 10-20fps difference between virgin brass and one that is shot for the second time. Do load development with the brass as bought and you will have minor adjustments on the next use of the cases.

Look at factory bought ammo that shoots small groups whilst fire forming.

 

[the big greasy]

Don't waste components on fire forming. It takes very little energy to blow out the case to fit the chamber. You might get 10-20fps difference between virgin brass and one that is shot for the second time. Do load development with the brass as bought and you will have minor adjustments on the next use of the cases.

Look at factory bought ammo that shoots small groups whilst fire forming.

Ok I will do so, thanks!

 

[cape cove]

I copied this from that link. PV=nRT is the formula for ideal gases, but it would apply here as well. You would need the full volume where the reaction takes place = fire formed case.

2. Always measure ACTUAL case capacity. If your cartridge capacity is less than QuickLOAD assumes, you can get pressure problems with loads identified as safe. Remember different brands of brass may vary in case capacity by up to three grains (with the larger cartridges). Don't even think of applying QuickLOAD-generated recipes until you've measured the ACTUAL case capacity of your brass. Montana Marine concurs: "The biggest tip I would give is to measure the water capacity of your fire-formed cases, and enter that data into the equation. Before doing that, my chrono'd velocities were typically 20-40 fps slower than calculated. After entering in actual water capacity, results are generally within 10 fps of calculations. For example, the default water capacity of the 30-06 is 68.2gr. My fire-formed Remington cases hold 70.5gr, fire-formed Norma cases hold 73.7gr. That is a significant difference."

. Case Capacity: The default H20 capacity for the 6BR case is 37.80 grains. However, when we measured our fired and full-length sized cases, the H20 capacity was 38.40 grains. This makes a HUGE difference in reported pressures. For initial fire-forming loads, use the 37.80 default figure. After that, measure the ACTUAL volume of your cases as they are actually loaded. Thus, measure the fired case (with fired primer) if you neck-size only. If you full-length size, then size a fired case (leaving the primer in place) and measure its capacity.

This is the section I was refering to. Taken from the same link. I'm not siding with one way or another just trying to get some info. That's the reason I asker Mike his take on this.

 

[Tripodmvr7]

Did not see that part with the 6BR. It is just logic that the expansion of the gas re-forms the case to the chamber size and each and every firing with the same make cases will be very close to that fire formed volume. You can even select a group of cases within a certain volume difference if you have time to select them that way. As an example one grain of difference in volume relates to about 17fps in a 375HH case.

 

[Mikecr]

There can be bigger MV differences with smaller cases, and some of us prefer to mitigate so much ES caused by outliers.

 

[jimbires]

Ok I will do so, thanks!

this is another good reason to do seating depth testing first . I haven't had any problems doing a seating test with virgin brass . then I have once fired brass to start powder work up .