Pressure question on 300 WSM

[Boisedoc]

Bonie I think you may be right. I looked at the rifling marks on my dummy round and they see more of a smudge. I still have it so may try the sharpie as well.

Thanks so much sedancowboy! My brother in law has a lathe, lives down the street and I just volunteered him!

 

[Boisedoc]

Was that the first loading of that brass? You are fairly low in charge weight compared to all the wsm's I have played with. Out of about a dozen they have all gotten over 65gr with 4831 and various 200gr class bullet. I shot a pile of 208amax and 208eld's from a couple of them, up in that same powder range.
The last rifle runs 66.3gr behind a berger 200.20x in adg brass, at 2905fps from a 26" barrel. I would think you would be close to 2650-2700 with that combo.
ADG brass is about the best you will find for the wsm, maybe one day lapua will make a wsm case.

That's the first load. I really think the bullet is too close to the lands. I have a long action so not limited in length

 

[tim_w]

That's the first load. I really think the bullet is too close to the lands. I have a long action so not limited in length

It's why I suggested to go with hrdy COAL to start with and adj from there given your erratic pressure issues. That will be sure to get you off the lands. After you can spend the time and workout what is just touching and from that you'll know your actual jump. You can adjust by moving 0.003 in either direction to see its effect on your groups once you have powder load node figured.

You really should take @sedancowboy up on his offer to drill and tap a fire case for you to use for checking bto to lands comparator. It's by far the most accurate way.

As a general rule of thumb you don't want to be in the ±0.005 the lands range. It is a range where wildly inconsistent pressure can occur. Some loads may kiss the lands instead of having jump and others may not be into the lands when you want them to be and instead has jump causing a pressure drop.

Many loaders will stay at least .007 min off to be safe. As a new loader 0.010 min is best. You can easily move in and out of the tune by increasing jump to tune it. Especially true of eld, hybrids etc. Only some vld really show a real preference to be @ or into lands at times.