I trim the cases a bit longer than 1.340 so that on fire forming the neck pulls back to 1.340 (there was some trial and error to get dialed in).
Winchester 22 Hornet brass did not need annealing, but PRVI brass needs annealing post forming, prior to fire forming.
I fire form with a case full (compressed load) of 4198.
Great info thanks... I am keen to start making up some 17 HH cases myself
Just got a Bullberry double ended neck forming die (.20/.17) and ran a couple of annealed cases through, followed by a final FLS using the Hornady die.
Came out quite well but wasn't sure how long to trim the cases... could you please advise how much longer than 1.340" they need to be before fire forming?
I also measured .22 Hornet cases, 10 each from Highland (Privi), Winchester and Remington. On average the Highland cases were .001" thicker in the neck wall thickness than the thinnest (Remington).
I also measured all the rim thicknesses... will post detailed data later today when I get home.