First time reloading in ages, 300wm

[fracguy]

Got a press and dies a while ago and had other things that came up so never got to press out any ammo. I have learned that just about everything I did a long time ago was wrong so been doing a bunch of reading, had head separation with my 300 wm years ago, thought it was just the way it was, would only get 4 reloads out of my brass and all developed a crack, learned that was due to headspace issues. So I don't have the competition shell holders or any of that fancy stuff so I messed around with my dies and a cigarette lighter. I set my dies and used a lighter to blacken the shoulder, if there was any resistance or markings on shoulder I turned die down by about 1/16 of a turn until I got just the lightest of marks and barley any resistance when closing bolt. Turned die down about 1/32 so just barely moved and got no marks on shoulder and bolt will just about fall closed. Got a box of 215 berger hybrids, and man oh man are they LONGGG . I am limited to length by my magazine, I did a very rough measurement with a piece of brass that sizes and used a punch to open back up so the bullet was a firm fit but movable. Bolt out (I don't have a coal gauge) I put round in and pushed it ahead until it stopped and used my cleaning rod to push it back out. Very crude I know but I can't make anything longer than 3.518 due to magazine anyways but curious, overall length was 3.696. My question is am I good to start my loads at 3.518 and get some nodes? I'm using r4831sc as it's mostly what I can get my hands on and seems to be the most temperature stable powder. Max load is 68.7gr with starting at 65. Start at like 66.7 and go up .5gr increments? I'm up for suggestions and tips. Using this on elk, not a target rifle. It's a weather by vanguard 300wm. Thanks in advance

 

[freezerfull]

So to clarify, you slammed the bolt closed on a round with minimal neck tension and got a measurement of 3.696” COAL? If so, I’d suggest doing again at .030” (3.548” COAL) longer than you mag length to confirm your not contacting the lands at that length at all. You likely won’t be but I’ve seen some weird leades and carbon buildup in throats that have done some funky things. If there is zero sign of land contact on the bullet with a 3.548” COAL, you should be okay to safely begin working at your max mag length of 3.518” without any suprises but will likely have a jump well in excess of .100”.

Regarding shoulder bump I’d highly recommend getting a comparator and calipers. Since they headspace off the belt, belted mag chambers can have some crazy variation in shoulder location (much more so with older rifles) and it’s worth knowing exactly where yours is in the chamber. I full length size and try to bump the shoulder .0015-.002 shorter than fired cases.