Ok, I'm still learning here, but this should be easy for every experienced reloader. On my 300 RUM Sendero ll, I'm having a hard time here with MAG OAL, LANS OAL, and what to load. My MAG OAL is 3.683. I've got that figured out. Shells WILL feed into the chamber from the magazine with reliability at 3.650 with no issues. Thats .033 under magazine which seems like A LOT! Do any of you go closer to MAG OAL without chamber issues? Now, I don't have the correct tools to measure ot the LANS. I grabbed a black sharpie, colored an accubond up, loaded a round WAY out to like 3.900. Round would NOT chamber. I finally got a round to chamber very very very tightly at 3.853, and I did see marks on the black colored accubond, but I'm pretty sure I was ramming the bullet into the rifleing. I could barely open the bolt. Super tight. So, I gradually seated the bullet over and over until I could NOT feel or hear the bullet sticking slightly in the lans on ejection. That came to 3.823. I would imagine that that is where my lans are, right? So, my loads will be at 3.650. My lans are at 3.823. I think. Thats .173 off the lans which I believe is HUGE. That should NOT create any pressure spikes, right? You have to be around .010 or dang near touching to create pressure, right? Please, if anyone can tell me if this has all done "somewhat" correct and I'm not going to kill my self, I would appreciate it. I think if I'm under Magazine OAL, I will always be fine. I don't think the mag will allow me to load to far out unless I'm shooting a single shot. Thanks so much for the help.