300 Win Mag Variations

[pearcetopher]

Hi guys,

I've started casting for my .300 win mag mossberg 4x4.
I am using the lee c309-160-R double cavity with 309 sizer and lee alox with gas checks

16 grains of red dot will give me a 6 inch pattern at 100 yards. I am a little dissapointed at the accuracy of this load. More red dot = wider patterns.

I know I should have slugged my bore first however sometimes that load will shoot 1" groups for around 20 shots and then they will go all over the place. I cannot figure out why sometimes they are very accurate and sometimes they are not.

Personally I believe its the hardness as these are dropped into water but are casted at different temperatures, thus resulting in varying hardnesses. Either that or I need a bigger bullet. Yes I am using straight wheel weights with no BHN tester.

Anyone know roughly what that mold will drop with wheel weights before sizing?
I always thought if it is a lee 309 mold then the largest bullet it will drop would be close to 309, or is that just an estimate Im thinking about buying a 310 sizer and maybe that will help.

Also does anyone thing heating these bullets air cool dropped in an oven would help the accuracy?
Also, I am getting no leading at all, barrel is clean.

Once I tried a 51 grain load of 4895 and it was more of a shotgun pattern, it had 0 accuracy

[ShooterAZ]

Here is some advise based on my experience with the 300 Win Mag (Ruger M77). I only got so-so accuracy with Red Dot, and scrapped it. Unique worked MUCH better on the my lower velocity loads 16-1800 fps. My best results in 300 mag were obtained with SR4759 and 5744 powders. I won't list charge weights here. I size to .311 for almost all of my .30 cal rifles/molds, and use Carnuaba Red lube . Your alloy may be a bit soft for the higher velocity loads with only alox. I was using either Lyman #2 or 2/6/92 alloy for serious target work. I have not pushed any of my loads past 2200 fps. Also, If you don't have a micrometer, you should consider getting one. You should also consider getting the Lyman Cast Bullet Handbook, or the Lyman 49th reloading handbook. The 300 mag is a bit of a challenge with cast, mainly because of it's very short neck. Most of the heavier boolits will need to be seated with the gas check below the case neck, which can be problematic. Good luck...Shooter