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 Post subject: Tweaking the seating depth when changing the Charge Weight
PostPosted: Thu May 16, 2019 3:30 pm 

Joined: Tue Sep 17, 2013 11:57 am
Posts: 819
Location: Campbell, NY
Has anyone developed a "rule of thumb" for tweaking the seating depth of bullet when you increase the charge weight?

I found a good load for the 300 WSM with Re-16 and the 180AB at 61.0 gr. Re-16 and a bullet jump of .110". That load was running around 2907 ft/sec. I upped the charge weight to 61.5 gr. of Re-16 and obtained a velocity of around 2934 ft/sec. However, I had three in and one out.

What does the collective experience say? More jump or less jump with the higher charge?

When I worked with my 7mm-08 with 140 gr. BT's, I found I had to increase the jump when I increased the charge weight. But that was a different cartridge with a different type of bullet.

Thanks for your thoughts.

Dan


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 Post subject: Re: Tweaking the seating depth when changing the Charge Weig
PostPosted: Thu May 16, 2019 6:42 pm 

Joined: Sun Dec 24, 2006 12:20 pm
Posts: 29087
Location: Northern Virginia
NYDAN wrote:
Has anyone developed a "rule of thumb" for tweaking the seating depth of bullet when you increase the charge weight?

I found a good load for the 300 WSM with Re-16 and the 180AB at 61.0 gr. Re-16 and a bullet jump of .110". That load was running around 2907 ft/sec. I upped the charge weight to 61.5 gr. of Re-16 and obtained a velocity of around 2934 ft/sec. However, I had three in and one out.

What does the collective experience say? More jump or less jump with the higher charge?

When I worked with my 7mm-08 with 140 gr. BT's, I found I had to increase the jump when I increased the charge weight. But that was a different cartridge with a different type of bullet.

Thanks for your thoughts.

Dan


I think you’re exactly right.

I would fire a few groups though to make sure the 1 out is really the load vs just an anomaly.

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 Post subject: Re: Tweaking the seating depth when changing the Charge Weig
PostPosted: Thu May 16, 2019 6:52 pm 

Joined: Sun Apr 04, 2010 9:59 pm
Posts: 4293
Dan my rule of thumb is to never change two different components at the same time. It confuses the data, and doesn't really prove anything unless the stars align with that change and your group size goal is magically met. Working up a load takes longer that way but once you achieve your goal you are pretty sure of the load. Good luck!!!

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 Post subject: Re: Tweaking the seating depth when changing the Charge Weig
PostPosted: Fri May 17, 2019 5:36 am 

Joined: Sun Dec 04, 2005 5:15 am
Posts: 61
When working up a load I have always tested the powder charge first starting with 2-1/2gr below max and going to max in six different 3 shot groups of 0.5gr increments. After I found the best powder charge is when I start testing different bullet seating depths. That has worked for me for almost 50yrs now.

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 Post subject: Re: Tweaking the seating depth when changing the Charge Weig
PostPosted: Fri May 17, 2019 9:49 am 

Joined: Tue Aug 16, 2011 2:13 pm
Posts: 1544
Location: center of Pa
I have changed my load development method on my last few work ups . I'm now using a starting powder charge and finding my best seating depth " FIRST" . then I work my powder charges "SECOND" . by using a starting powder charge you are most likely not on any node . so I know I'm only testing seating depth . when I find my best seating depth I work powder charges . so far my determined seating depth has stayed the best , or very close to best ,through the powder charges . I've even switched powders and seating depth held true . another thing I've found by finding seating first , is I can test seating while I'm fire forming new brass . the seating testing does not seem to be affected by using new brass , powder testing is definitely affected by using new brass . I learned this a long time ago ; always start testing at either magazine length , or about .005" jump to the lands whichever is shorter . by starting at max cartridge length there is only one way to go to fine tune seating depth , this is a shorter COAL . it takes the guess work out of it .

I think by finding powder first , then seating , you are finding best seating for that powder charge . if you change powder charge , you need to change seating depth .


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