case stretching - What is normal

[egraham]

I have a remington 700 built with a 1/8 douglas match ss barrel. I bought 500 pieces of brass made from lc 5.56 brass. I trimmed them to 1.350 and then fireformed in my gun using 208 grain amax's at 1030fps.

How much should my cases stretch after fireforming? Do whisper cases need trimming after every firing or once fireformed do they tend to be ok for a few reloadings?

Thanks