Case Triming Before Fire-Forming

[Gergg]

When you fire-form a case for the first time(220 Russian to 6ppc) should the case be trimmed to a particular length before the first firing or wait until after. I ask as I already trimmed mine to approx. 1.498 and then started wondering if the cases change length after the first firing. I've read that a range of 1.490-1.495 is the standard final length of the cases after forming. Just trying to figure all this stuff out before I either ruin something or hurt myself.

 

[BoydAllen]

If you are using the step in the turning mandrel as a stop when you are turning the case neck before fire forming, you probably should trim your cases to a length where there is a little bit of cut on the shortest case, and then position the mandrel so that you get the length of cut that you want, so that it stops where you want it to relative to the shoulder. But...if you do as I do and turn by eye, then there is no reason to. After fire forming all of your cases will be shorter than before, and I find a good clean-up length to be 1.490.

 

[Joe R]

Hi Gergg,
I assume you've looked at this http://www.6mmbr.com/6ppc.html and this http://forum.accurateshooter.com/index.php?topic=3780388.0 Don't forget the previous owner of that rifle, have you spoken to him lately?

Joe

 

[Gergg]

Hey Joe....yeah, I've read all that stuff, just seems like there are always little details missing that my mind keeps bugging me to clarify, hence the unending questions...lol

Boyd(or anyone else).........how much do the cases shrink after fire-forming? That is one of the thoughts that crossed my mind as I was trimming the cases before forming.

 

[artbosco]

When you fire-form a case for the first time (220 Russian to 6ppc) should the case be trimmed to a particular length before the first firing or wait until after. I ask as I already trimmed mine to approx. 1.498 and then started wondering if the cases change length after the first firing. I've read that a range of 1.490-1.495 is the standard final length of the cases after forming. Just trying to figure all this stuff out before I either ruin something or hurt myself.

I first trim all cases to a specific length [the shortest length of my necked up brass]. Then adjust my turner for neck length, so that all necks will be turned into the shoulder the same amount. When done with the second fire forming, I trim to my final desired length.

 

[Gergg]

I first trim all cases to a specific length [the shortest length of my necked up brass]. Then adjust my turner for neck length, so that all necks will be turned into the shoulder the same amount. When done with the second fire forming, I trim to my final desired length

Do you have any idea how many 1000's I should expect the case to shorten after 2 fire forming rounds?

 

[Joe R]

I first trim all cases to a specific length [the shortest length of my necked up brass]. Then adjust my turner for neck length, so that all necks will be turned into the shoulder the same amount.

I believe that you should only turn into the shoulder once. If you keep turning into the shoulder every time you turn you run the risk of weakening the shoulder or worse when you fire the neck of the case could separate from the rest of the case and jam into the barrel. I've heard this warning but not actually seen anyone experience it. It made sense to me, so after my first turning I backed off the cutter a bit.