300 Wby seating depth

sailorjim

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Joined
Dec 26, 2015
Messages
32
Using a 200 gr bullet, I would have to seat way beyond magazine length to touch the lands. I'm loading hunting ammo and want to stay inside magazine length. Given these restrictions, have you found seating depth to be a large factor in accuracy?
 

Jud96

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Jun 30, 2013
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Holt, Michigan
Seating depth in my opinion and experience is the biggest determining factor in accuracy. So yes it’s a HUGE factor in accuracy. For your .300 WBY, if you want to use your magazine this is the process I would do. Measure your inside length of your magazine box, then load your rounds .020 shorter than that for reliable feeding. That’s where your seating depth starts out. Then from there progressively seat your bullets deeper in .005 increments until you find the sweet spot and your groups start to shrink. Once you find the seating depth that shoots the best, load up some rounds and shoot some groups to verify the accuracy. Keep good notes along the way and once you find your most accurate seating depth, start working on powder charge to find the velocity node. If you need anymore help ask questions and we will help you out! 👍
 

Texanjohn

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May 6, 2012
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116
Location
SE Pa.
Jud96 is spot on, Weatherbys have a long freebore, one of the ways they get velocity, most must have the “jump” to get claimed performance, it’s not a bad thing, it is what it is, work with it,most can be made to shoot very well, mine have accounted for lots of DRT shots
 

sailorjim

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Dec 26, 2015
Messages
32
Thank you. Your information is taken to heart and that will be the process that I follow.
 

asd9055

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Nov 15, 2013
Messages
362
Location
Texas
Weatherby cartridges are designed for super long free bore. Not supposed to load to the lands.
I load both 300WBY 180 and 200 to 3.56" COAL and get less than 1/2" groups
With one of them I get 0.432" groups at 200 yards
 

Warbird2006

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Joined
Apr 15, 2012
Messages
332
Seating depth in my opinion and experience is the biggest determining factor in accuracy. So yes it’s a HUGE factor in accuracy. For your .300 WBY, if you want to use your magazine this is the process I would do. Measure your inside length of your magazine box, then load your rounds .020 shorter than that for reliable feeding. That’s where your seating depth starts out. Then from there progressively seat your bullets deeper in .005 increments until you find the sweet spot and your groups start to shrink. Once you find the seating depth that shoots the best, load up some rounds and shoot some groups to verify the accuracy. Keep good notes along the way and once you find your most accurate seating depth, start working on powder charge to find the velocity node. If you need anymore help ask questions and we will help you out! 👍
 

Tulsa Reiner

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Joined
Jan 6, 2014
Messages
327
Location
Tulsa, OK
Weatherby cartridges are designed for super long free bore. Not supposed to load to the lands.
I load both 300WBY 180 and 200 to 3.56" COAL and get less than 1/2" groups
With one of them I get 0.432" groups at 200 yards
asd9055: what make a model of bullets?
 

rsnell

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Joined
Oct 24, 2014
Messages
70
Weatherby lists the free bore of a 300 Weatherby magnum as 0.361 inches. You will never get close to the lands. Use the seating depth listed in the loading manuals.
 

MagnumManiac

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Joined
Feb 25, 2008
Messages
2,344
Yes, the SAAMI freebore is less than Roy’s designs. Most had 1/2” freebore, the 378 had 3/4” and the 460 had 1” when first developed, but was dropped back to 3/4” when in full production.
I had my reamer made with 1/2” freebore for my 375 Bee. Works a treat too.

Cheers.
 

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