Seating Depth and Range testing

[Apothus]

So I have a Remington 700 Sendero in .300 RUM that I'm building a load for. Last weekend the OCW test was done at 349 yards with loads starting at 77 grains of Reloader 25 and going up to 80.3 grains in .3 increments. The best charge was determined to be between 79.4 and 79.7 grains. To touch the lands, the ogive sits at 3.850, so I started at 3.830 and that's what I shot the OCW with. Now that I got my 2 best charges, I settled on 79.5 grains of powder, and I'm moving on to bullet seating depth. I seated 3 different seating depths with 10 thou, 30 thou, and 50 thou off the lands to see which one gives me the best accuracy, and now this is where my question comes in. I was told that I should test at 300 yards and see which depth is the most accurate. Unfortunately time is short, and can only get 100 yards at a local range, so can I shoot these seating depths at 100 yards and get reliable enough data to see which one is going to be most accurate for me?

Thanks for your input
Tom
P.S Yes I know these are well beyond mag length, but 1 at a time is good enough for me, this is a distance gun, not a large quantity gun

 

[lancetkenyon]

Not sure what bullet weight or velocity you are shooting, but here is MY load for MY .300RUM. Yours may vary. My load is technically over book max, but no signs of pressure. Factory barrel and chamber on a Rem. 700.

 

[dustinoif3]

I recently developed a load for a friends 300win mag. I was at the 100y line and watched a 1" group shrink to .5 during my seat test. Distances I used were 30,60 and 90 of the lands. Still waiting to get out to 300 to verify

 

[Dan Newberry]

You can check it at 100 yards, not problem.

Seating depth increments of .005" ought to be enough to steer the barrel time onto a static node of the harmonic vibration of the barrel...

Look for a seating depth that will put the cold, clean bore shot into the same group that follows, and that'll be a winner at longer ranges as well.

Dan