Depth seating 300 win mag

richwfrost · Feb 27, 2012

old model 70 300 win mag,,,, 200 # AccuBond "0" head space length is 3.605"......my magazine maximum length is 3.400"...SAMI is 3.340"...I have tryed some at 3.380" (.020 under max magazine length) and get a little better results than at 3.350"....Do small head space changes make much difference when there is .200" head space.....Rich

joelkdouglas · Feb 28, 2012

Rich,

Seating depth does play a big role in accuracy, but I don't know the answer for your rifle. I load for a .30-06 that has a long magazine, so I have no issues getting to the lands.

I assume this is a hunting rifle.

However, if I were in your shoes I would seat a bullet .308 inches INTO the head of the case (measure overall bullet length, then keep seating progressively deeper until the bullet length minus .308 was left out), assuming that will run through your magazine. If it wouldn't fit in your magazine I would continue to seat deeper until the round fits and feeds reliably.

Then I would start experimenting, moving the bullet deeper by 0.01 or so, or whatever you wanted, to see what happened. You'll probably find some improvement somewhere there.

v/r
Joel

Elkman · Feb 28, 2012

I load mine as long as they will function in the magazine. Back them off as long as you can.
I you have some on hand try H-4350 with a good 180 gr bullet and start at about 68 and work up one grain at a time. My 300's "love" 4350

ridgewalker · Feb 29, 2012

richwfrost, I had the same problem years ago with a new model Win 70 in .300 Win Mag. Using it like a single shot rifle with bullets seated about .020 off the lands it was extremely accurate, as in 1/2" groups. That said, they wouldn't fit the magazine, so I sacrificed the accuracy and seated them deeper. I don't remember how far off the lands they wound up at, but it still shot 3/4" groups from a bench. I considered that plenty good for hunting and from there it killed many antelope, deer, elk and everything I pulled the trigger on.

A friend has a "longbow" Mdl 70 which shoots extremely well, but it is a dedicated target rifle and a single shot at that.

Good luck in your efforts.

hubcap · Mar 2, 2012

As much as I perfer 200 grain bullets in the 300 I,ve found the 180 protected point Partition works real good when loading shorter than 3.400. Nosler makes this bullet just for the 300 mag. The 180 leaves plenty of room for powder while the 200 AB eats up powder capacity real quick when seating below 3.400. Works nice with removable magizines which seem to made too short more often than not. I guess the downside would be the lower BC for the 180 PP PT. :idea:

SJB358 · Mar 3, 2012

hubcap":2mhfvj8f said:
As much as I perfer 200 grain bullets in the 300 I,ve found the 180 protected point Partition works real good when loading shorter than 3.400. Nosler makes this bullet just for the 300 mag. The 180 leaves plenty of room for powder while the 200 AB eats up powder capacity real quick when seating below 3.400. Works nice with removable magizines which seem to made too short more often than not. I guess the downside would be the lower BC for the 180 PP PT. :idea:

That 180 PPT with RL22 has worked very well for me as well. You give up a little BC but they are some excellent bullets for the 300WM.