Load development question

dartshark

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Dec 13, 2011
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Just getting started reloading and need some advice.

I want to develop a load for my 300 Weatherby MK V (USA)
I’m using once fired Weatherby brass tumbled\polished
Primer pocket and hole uniformed\cleaned
Neck sized
Federal 215m primers
IMR7828scc powder
Nosler Accubond LR 190 bullets


I have determined by measuring and reading that I there is no way to load a round even close to the lands and that Wby’s perform best with a jump. So I’m looking to load the best I can that will still feed through the magazine.

I measured my magazine (3.730) and was going to load 3-5 at 3.700, 3.650, 3.600 and 3.550 OCL to see what it likes better.

My question is when trying different jumps should I at the same time be trying different amounts of powder at each jump or should I try to figure the best jump first and then vary the amount of powder?
 

dartshark

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Dec 13, 2011
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I would work up to pressure first. Then try what you are thinking about doing. Make only one change at a time.
Again, bare with my rookie self.
By working up to pressure, do you mean at one length, and then try other lengths?
Using a set amount of powder does the pressure change much with seating depth?
 
Last edited:

Zen Archery

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Dec 27, 2012
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Pressure will change with both powder weight and seating depth.

You can get super OCD when loading to the point of inefficiency with time, money, and materials.

Figure out your goal: hunting, target, distance, etc. with that caliber you are gonna have to start pushing it way out there before needing to get super OCD about pressure.
 

3stooge

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Jul 21, 2012
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Myself, I first like to figure out what seating depth the bullet likes best. Then once the depth is determined, then I adjust powder charges to determine the optimum charge weight. Some people like to do powder adjustments first and then adjust seating depth.

I would start out at 10% below max book load and do a bullet seating depth test first. My 2 cents worth anyway.
 

Rich Coyle

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Aug 14, 2013
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I would work up to pressure first. Then try what you are thinking about doing. Make only one change at a time.

I would load up about ten with a chosen powder and maximum length for your magazine. Start with the slowest one you would accept and load each one with 1/2 grain more until the bolt is the slightest bit sticky, the primers are no longer rounded on the edges, or there is a scrape of brass at the ejector hole. Once there back off a full grain. Now you can check for over all length with no more than three shot groups of each length. If it won't fire three close together it won't fire more. In fact if two are not even close I wouldn't fire anymore of that length. One time I had one come in .180" from the lands with a custom barrel. Another came in at .120" from the lands. Next I would load up three of each primer I have and duplicate the above effort.

Once you establish the over all length with that bullet it usually stays consistent for that bullet even with different powders.
 

Dosh

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Aug 6, 2013
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Dart, Weatherby rifles in Weatherby calibers have freebore which is too long to allow a seated bullet to touch the lands. The 300Wbys I've loaded for are quite accurate at mag length or less. Measure your loaded rounds at the ogive with a comparator, most bullets vary in length too much to do OAL. Good luck
 

dsculley

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Feb 13, 2014
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Orange Beach, AL
You could start at magazine length and then test for seating depth with the method described in a thread on the accurate shooter/shooters forum - http://forum.accurateshooter.com/threads/here-is-my-tip-on-how-to-find-ideal-seating-depth.3933366/

This method will help locate a seating depth that works independently of powder charge. I recently read this thread and I like the method. This is kind of like using an OCW test to find your optimal charge. Sometimes when you test seating depth with just one powder charge, the optimal depth will change once you work up your optimal charge. At least I have had that happen. Other opinions may vary.
 

dartshark

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Dec 13, 2011
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Thanks to all for the advice!
I got the neck bushings I needed yesterday and the LabRadar chronograph is suppose to be here tomorrow.
Good thing it's a three day weekend, I have lots of time to test and maybe still get out for a day of archery deer, which opens tomorrow.
I love fall:):):)
 

Kansaswoodguy

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Aug 26, 2014
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I load for a lot of semi auto guns. Just load the bullets at just under max mag length and adjust your powder charge only to find the accuracy node and more or less forget about adjusting seating depth. I can usually find a a sub MOA powder charge using this method now I do find some bullets a given gun doesn't care for and stick powders seem to give me the best accuracy.
 
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