Re: 7 mm STW powder choice , Has it been Covered
These are at the maximum levels. The H4831 load was created by me before load data was published. I used some dead reckoning off of the 8MM Rem Mag. I also have gone back to H4831SC for everything and every weight from my
.25-06 Rem. through the .30-378s. An old reloader 27 years ago taught me the benefits of it and after some experiments, I kept going back. It is the powder for me. I blast my 150 grain Ballistic Tips out of the .30-378 guns below at a little over 3700 FPS. That said:
H4831 is 81.5 grains for a 140 grain Nosler Ballistic Tip
H1000 is 82.0 grains for the same bullet
H1000 is 80.0 grains for the Nosler Partition and
H4831 is 76.0 for the same bullet
All used Winchester magnum primers are trimmed to 2.84" with an overall length of 3.575". It might be obvious, but the cases are also chamfered and deburred. Sierra bullets in the same weights can be used as well.
Out of my 2 26" barrels, here are the average speeds from my chrono:
140 with 4831 - 3510
140 with 1000 - 3405
160 with 4831 - 3350
160 with 1000 - 3255
I haven't cracked a case (4 or 5 loads per case and they all seem to need to be cut back about .11" when done with sizing - been working with about 250 cases. Some 8MM-based cases and some STW cases.
One trick I also learned many years ago to create a good fit and and tight fit for uniform chrono speeds is to hold a bunch of bullets in your hand to create a sweaty situation. That sweat will lock-in and provide some very consistent pressure levels. As a sidenote, if you ever try to pull a bullet, you'll see the difference from those not locked-in.