Any tips on Down loading a .300 WSM


January 3, 2003, 12:24 AM
Looking to loaad a subsonic for the 300 WSM, weight of bullet not a factor, the heavier the better. Only req. would be that it be stable and subsonic. I have heard that there are more than a few tricks to keep the loads safe while going slow.

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January 3, 2003, 06:10 AM
by finding loads for a .300 Whisper

Either stevespages, SST's Rifle room, or Centerfire Central

Steve Smith
January 3, 2003, 12:41 PM
.300 Whisper loads could give inconsistent ignition. Be careful. Might need a case filler, or just bigger powder. I know nothing about "downloading" but I was concerned about the .300 Whisper data.

January 3, 2003, 04:35 PM
prolly shudda thrown that in...

if the loads are more than 10% under, you might look at case fillers (kapok)

just thought of something might look at cast bullet info

some of them are pretty low velocity. Problem is that the WSM is so new that it's not listed in the Lyman book

January 3, 2003, 05:24 PM
I use Alliant`s 2400 for downloading any of my rifles. I use 16 grains in 303 brit, and 20 grns for 30-06, with cast bullets w/gas checks. 2400 works well with light charges in bigger volumed cases, without the fear of detonation, and is pretty position insensitive. I know others use 4759 for reduced loads, havent used it myself, but worth a mention. Let us know if you find a good load, Ive been wondering about how the short-mags handle loading down. (Not nessisarily sub-sonic, but light loads)

January 7, 2003, 01:52 PM
Yees as quoted in the last posts, the 300 Win Short Mag is the beast I refer to and detonation is why I ask. Want to avoid that at all costs. I knew that the whisper data doesnt apply as the case volume is entirely different. Definately looking for something on the heavy end. 180 Gr and heavier going just under the sonic boom range. Any help or past experiences as relate to this are appreciated.

January 7, 2003, 02:39 PM
You're going to have trouble keeping any subsonic bullet stable in a rifle that's barreled for .300WM velocities. The twist for those is presumably somewhere in the 1-12" range, maybe slower, to accomodate the faster bullets. You can try using really light bullets, but those slow heavies are going to wobble like nobody's business.
I know that it isn't the answer you were looking for, but I'd really try a different case when working with subsonics. Try the 7.62x39, or the Whisper type cases. Maybe even the .30carbine.
If you do decide to experiment, cast bullets are probably the way to go. NRA used to recommend kapok or dacron as fillers when shooting cast loads of pistol powders in rifles.

January 8, 2003, 10:39 AM

Sorry I just had to

January 8, 2003, 03:35 PM
The best source of info and procedure is going to be the Lee Reloading manual. It has wonderful info on down loading such as computing approx. velocities and powder charges, powder selecton, ect. For base data just use the .300 WinMag. as it is very close to case capacity of .300WSM.
The problem is not so much with KB's from the unrepeatable phenomon of "detonation", but from double charges with small charges of fast burning powders.
BTDT !!!
Last August, I was loading some plinking/practicing loads for My Interarms MkX in '06, with some 175 FNGC bullets. The 12.0gr load of Universal got doubled in one.
Locked the gun up tight !!!!!
Only damage was to small projection off of bolt face next to extractor cut. It sheared off while bolt was being hammered open. A local auto speed shop magnafluxed the action for me... it checked out with a no-go headspace gauge too. Whenever CharlesDaly starts importing the Zastava guns and parts, I'm going to get me an new bolt and intall a .338/06 bbl I have.

When loading the reduced loads, double check for powder level. More than one gun has been KB'd with double charges of pistol powders.

If you're looking to load down to 7.62x39 levels, the old standby powder for reduced "intermediate" loads is H4895 (also the IMR). If your' looking to load Cast Bullet Loads, the Lyman Cast Bullet manual is a wonderful reference. Just use the .300WinMag data, and consider maximums to be 5% under WinMag loads till you work up to them. Most maximums are not due to pressure but practical upper limits for cast bullet velocities. Most of the same weight bullets can be substituted with jacketed, but be sure to observe the 5% caveat I just mentioned.
Good Luck !!!!

BTW I've not gotten any benefit from fillers (w/.22Hornet- thru .45/70). If I were to try them again, I'd go with Puff-lon for a try.
If you can cast, the Lee .311" 155 Pt. gas check bullet over 5-8gr of Unique will probably be your best bet. Not the heavy bullet you're looking for, but will stabilize at the speeds your talking about (900-1,000 fps). You could just use bullets "as cast",and lube w/Lee Tumble lube for an accurate and very inexpensive load. I've done this w/'06 and this bullet and a .311 RN 78gr bullet. The 78gr'r w/5.0 bullseye would print to my lower taper of the crosshairs of my 2.5-8x Leupold for a wonderful plinking load. Would shoot ragged hole groups under 1" @25yds too.

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