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Old October 28, 2001, 05:34 PM   #1
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Join Date: May 25, 2001
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.300 Win Mag reloading questions

I am new to .300WM loading, (just bought a 700P to move up from DCM matches) so I did quite a bit searching through older posts on this subject and have come up with a list of ideas. However, I still have a few questions.

So far I have decided to use Lapua brass, RL-22 powder, Lee Collet dies, a Forster ultra seating die and Sierra bullets.

1. A few posts mentioned that new brass must be FL resized before use. Is this always true or only for new brass that will not chamber?

2. With .223 I have always shot the heaviest bullet that would still fit in a mag. Is it the same for the .300, should I be looking at the 220gr for long range matches?

3. I have a ton of H335 that I use for .223. None of the reloading manuals or Hogden shows a .300WM load for this powder. They do however list loads for .308. Have any of you worked up a load for the .300?

4. Any load recommendations or other advise?

I have been loading lots of pistol calibers and .223 on a Dillon 650 for many years, but this will be my first foray into the larger rifle calibers. Thanks in advance for your help.

Last edited by locolife; October 28, 2001 at 08:29 PM.
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Old October 28, 2001, 06:23 PM   #2
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Is that Winchester or Weatherby Mag?

If it's Winchester, perhaps I can help.

I own a .300 Win Mag Laredo, and have found the following out about the rifle and caliber.

First, the .300 Win Mag is capable of outstanding accuracy--but, usually not with factory loads! Why? Because, for some reason, most .300's are designed with very long throats. Long Range rifle accuracy is usually found to be best when the bullet is seated to within a short distance of the lands, or barely touching. The max recommended OAL for the .300 Win Mag is 3.340. That is usually the longest seating length to get the cartridges to still fit into the magazine.

My rifle likes IMR 4831, 70.0 grains, using the 175 grain MatchKing seated to an OAL of 3.510. I also use Standard Match primers. Federal seems to be the most consistent, although I have had good luck with CCI Benchrest also.

Also, I have found that my rifle likes factory new cases. It will shoot neck sized cases just fine, but for the best accuracy, I use factory new cases. Be prepared for a lot of experimentation.
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Old October 28, 2001, 08:31 PM   #3
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Its a Win Mag...
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Old October 30, 2001, 09:47 AM   #4
Paul B.
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Locolife. The reason you do not see loads for the .300WM using H-335 is because it is too fast a burning powder for the cartridge.
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