I have successfully necked down some Lake City .308 brass with headstamp LC 09 into reliable 6.5 CM brass. I ruined a lot of brass getting it right. Also the memory of the brass can fool you in that it will spring back after you run it through the die, so you have to measure repeatedly to make sure it's right. Also, the LC 08 brass is a little softer than the 09 and indented a lot of shoulders (1/3 of them) but only about 1 in 100 of the 09 dented significantly. Here's what I did: First I used a Redding Full Length Bushing Die (s-type) and removed the bushing. This allowed me to neck down the .308 in one pass without getting a lot of crimped shoulders. The neck elongated freely up through the die. I used sizing wax instead of spray lube. Then I ran them through an RCBS Small Base Die. Then I trimmed them on a Forster trimmer. Then I turned the necks on the Forster trimmer with the neck turning adapter to .289. Then I used a Wilson Chamber Gauge and the ones that weren't flush with the gauge I re-ran through the Redding die with the .289 bushing and double or triple pulled them (ran them through multiple passes on the die). The better lube (but not too much) the better they resized consistently. It was common to get headspace variations of up to .005 from the smallest to the largest, but none shorter than the target length (and most within spec) before I ran them through the Redding die again. Most landed at the value I set the die to but some sprang back pretty far. I used a Hornady Headspace Gauge to measure them with the D .400 adapter attached. I used a factory Hornady unfired casing as the standard for length, headspace, and neck diameter. The Wilson gauge was the final test and if they lay flush with the gauge they worked. If they were proud in the Wilson, they might not fire due to not going into battery completely. At this point I would recommend you anneal them to be perfect, but I haven't done that. I used LC brass because of the durable rim. I have a repeater and it tore up the Hornady brass. You could neck down Lapua brass this way as well, but I have heard that Necking up .243 or 22-250 is more reliable. But you have to fire-form them. I never want to fire form anything.