I was looking at different 7mm STW loads that are listed in my Nosler Manual and I noticed that majority are slower than the factory load I currently shoot (3100 fps). the most accurate powder tested for the 160 gr Accubond was H1000 (i think, this was last night and I am now at work) and it was listed at 2950 fps. Now I know that isn't a lot but the whole reason I went with the STW was speed and power. How much will 150 fps really effect a bullet with a BC of .531? I know that it takes the 1200 ft/lbs at 3100 fps at 800 yards and turns it to 1200 ft/lbs at 700 yards. Will the slower load increase barrel life? As you can tell I am new to a lot of this but i am trying to do the best I can.

According to my ballistic software, the bullet at 2950 will be about 1.5" lower at 300yds and about 3" lower at 400yds, both sighted in at 2.5" high at 100yds.

Yes, in theory the slower load would have longer barrel life.

BTW, if you don't have access to a chronograph, then it's dangerous to assume that the velocities published in the manuals, or the velocities published for the factory loads are correct. Individual rifles can very a LOT!

Modern reloading manuals are written to not get sued. Accurate load suggestions are usually given in the lower velocity accuracy nodes. You can find your own max by watching your primers and feeling for a sticky bolt lift during load development.

Chronograph. I have never used one but did recently inherit one. How do you know it is correct?

The only way to know for sure is to fire a round with a known velocity thru it. But IME, they are generally right on...or if there is something wrong (like interference from bright sun), they are so far off that you know there is something wrong.