RE: Having problems w/ 300 Win Mag
 

Handloader1, yes, and no. I had heard somewhere that with belted cases, it' s best to full length resize since they seat on the belt.

RE: Having problems w/ 300 Win Mag
 

Right off the top of my head the only cases that needs to be sized to headspace off the belt is the 300, and 375 H&H Mag. because of their shallow shoulder. According to the " Speer Reloading Rifle & Pistol Manual #12" " Modern belted Magnums like the 7mm Remington Magnum and the 300 Winchester have adequate shoulders for headspace control so the belt is actually more a cosmetic feature than a design necessary.
To get top accuracy from your belted magnum use the method described above to assure that the case headspaces on its shoulder instead of the belt."

If you neck size you will positivly be headspacing of the shoulder. Most die' s instructions for setting them up are for headspacing off the shoulder; be it full sizing or neck sizing. When people complain about belted magnums having to be sized off the belt to controll headspace, they are either trying to sell something, or are uninformed. A belted magnum case is just as accurate as a nonbelted case because one does not have to headspace off the belt; excluding cases simular to H&H Magnums. Good luck.

RE: Having problems w/ 300 Win Mag
 

Your problem is obvious! It' s a Hornady press! It is programmed to only use Hornady brass.[&:]

RE: Having problems w/ 300 Win Mag
 

I had a similar problem with a set of Hornady dies for a 6mm/.284. Although this isn' t a belted case, the problem may be the same. After repeated neck sizing, the cartridges began to be hard to chanber as the bolt was hard to close. Full length resizing didn' t correct the problem as it should have done. After making some measurements before and after the full length resizing process, I discovered that the F.L. die was not bumping the shoulder back. Hornady recut the die face by a few thousandths and everything worked just fine.

To measure for this, I used a trimmed .45 ACP case that I placed over the neck of the .284 case so the .45 case mouth rested on the shoulder of the .284 case. Then I used a caliper to measure the total length before and after F.L. resizing. The measurement showed that the case shoulder had not moved at all, so that proved that the F.L. die wasn' t contacting the neck as it should have. Hornady agreed that the problem was in the die and offered to recut the face ot the die as I requested. With .005 removed from the die face, it bumped the shoulder back approx. 0015" which then allowed the resized cases to chamber easily. If the shoulder had moved too much, I could have corrected that by backing the die off the shell holder by some small amount.

I know this is rather lengthy, but the measuring described took less time to perform then it took to write this. Hope this helps.