adjusting seating depth for accuracy


Well-Known Member
Jul 17, 2001
Walla Walla, WA
My 300 Win Mag shoots the 200 grain Nosler Partition best at 0.030” off the lands. I have tried 0.015 through 0.040” off and 0.030 was most accurate and is quite good (1.7” groups at 250 yards). None of the other seating depths tried were acceptable. Unfortunately my magazine box is too short for the cartridge loaded at that length. So I wonder if I could maybe find another sweet spot with the bullet seated deeper. Should I bother trying loads with the bullet seated deeper? If so what would you recommend for seating depth increments? Should I go in 0.010” or 0.020” or 0.040” increments initially or what? My box length is 3.6” long. I know that many 300 Win Mags have boxes only 3.38” long or so and yet presumably people can get them shooting well with a standard chamber (which would give them about 0.220” jump to the lands). Any suggestions? Thanks, Rufous.


If you have a gunsmith nearby or if you can do it yourself I would suggest milling the back side of the action to increase the length of the magazine well to accomodate the OAL of your cartridge. I did this with a friends 300 Tomahawk becuase of the VLD style bullets used in it, magazine well length was to short and he wanted to be able to use it in a repeater fasion.
You must also remove the same distance from the bolt stop so your bolt will actually move back to catch your case. It worked great for my friends gun and we can now shoot VLD's at any length without worring about them being smashed in the magazine well. I took out about .530 thou from the back side of the actions magazine well. If you go more than that you may need to manufacture a new bolt stop because the factory one does not have enough material left over.
Your question doesnt state what make of rifle this is, and that may be a determining factor if you can indeed use the above method to solve your problem.
Other wise youll just have to seat your bullets deeper.