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COL, and brass capacity. Important Considerations.

 
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  #8  
Old 04-29-2009, 05:52 PM
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Re: COL, and brass capacity. Important Considerations.

Quote:
Originally Posted by 3006savage View Post
I have always had questions regarding seating depth and the max pressure. I seat .01 from the lands typically. How close do you have to be before you start to see pressures rise typically? I like to seat bullets out as far as possible to maximize the usable case capacity but dont want to increase pressures due to seating depth.
It depends on a bunch of variables. I always work up my loads over a Chrono and adjust my seating depths over a chrono. I use velocity as the only objective measure of pressure at my disposal. I usually try to stay away at least .01" and I've not seen that distance cause pressure spikes IN MY RIFLES. I did get a batch of bullets once that had quality control issues. I was about .005" from the lands and one out of every 20 or so bullets had an ogive that put them closer to the lands and I was getting a sticky bolt and higher velocities. I seated all the bullets another .005 deeper (at .01" from lands) and the problem went away. I don't know how close those bullets where to the lands, or if they were touching, but the chrono is a great measurement tool for more than just velocity.

To answer your question, I first find out where the lands are and do my load work up at .015" away. I'll move out to as close as .007" when I'm tweaking my final load. If that doesn't help, I normally move back to .015" away and call it good.

AJ
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Old 04-29-2009, 09:01 PM
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Re: COL, and brass capacity. Important Considerations.

You can also adjust the burn rate, Ba ,to more closely correspond to the powder lot you are using.
It works best (safer) If you have numerous chrono readings as you are working up a load. Then you can tweak the Ba to more closely match your numbers.
When you change the temp it will allow you to temporarily change the Ba., without affecting the default value.
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Old 04-29-2009, 11:25 PM
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Re: COL, and brass capacity. Important Considerations.

Quote:
Originally Posted by RockZ View Post
You can also adjust the burn rate, Ba ,to more closely correspond to the powder lot you are using.
It works best (safer) If you have numerous chrono readings as you are working up a load. Then you can tweak the Ba to more closely match your numbers.
When you change the temp it will allow you to temporarily change the Ba., without affecting the default value.

RockZ,

I've not used that capability, it's nice to know.

Thanks for posting that info,
AJ
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  #11  
Old 04-30-2009, 07:46 AM
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Re: COL, and brass capacity. Important Considerations.

AJ,
I'm going to post a new thread with a great link that shows the best way to use this feature.

Rock
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  #12  
Old 05-01-2009, 08:44 PM
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Re: COL, and brass capacity. Important Considerations.

That could well explain why a guy I work with hasn't blown his 300 RUM up in his face by stuffing 100.5 gr of Retumbo behind a 180 TSX. Still, he doubts that the ejector marks in the brass are a real danger sign. He says it makes it easier for him to tell how many loadings his brass has been through...
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Old 05-02-2009, 03:19 AM
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Re: COL, and brass capacity. Important Considerations.

Very informative thread AJ, but there is one area I look at a little differently. I look at things like extractor marks, flattend primers and stiff bolts for signs of exessive pressure rather than chono speeds.

There are a lot of varibles when it comes to speed, such as bullet design, chanmber and bore design and quality, etc. Not to mention chrono's can differ fairly significantly.

If I'm wrong in my approach please explain.

Thanks,

Mark
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  #14  
Old 05-02-2009, 09:55 AM
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Re: COL, and brass capacity. Important Considerations.

Quote:
Originally Posted by MontanaRifleman View Post
Very informative thread AJ, but there is one area I look at a little differently. I look at things like extractor marks, flattend primers and stiff bolts for signs of exessive pressure rather than chono speeds.

There are a lot of varibles when it comes to speed, such as bullet design, chanmber and bore design and quality, etc. Not to mention chrono's can differ fairly significantly.

If I'm wrong in my approach please explain.

Thanks,

Mark
There are tons of variables other than pressure that affects extractor marks and sticky bolts. Cleaniness of chamber (how much grip the brass gets), softness of the brass, how much it's been worked before, bolt head condition etc.

In the past, I also used visual inpection of the brass, case head measurement and bolt lift/extraction as pressure signs. A couple years ago, I read an article about pressure and it changed my entire perspective on pressure/velocity and pressure signs.

Here is a link to the paper.
http://www.shootingsoftware.com/ftp/...%2019%2004.pdf

I still monitor my brass and extraction, but I rely more on velocity. As long as I'm using an appropriate powder/bullet combination for the rifle, with published loads to compare velocities with; I trust the velocity I'm getting is a very good indicator that I am in a safe zone. I don't try to push my 7mm-08 to 7mm Rem Mag velocities or my 7mm Rem Mag to 7 RUM velocities. If I want more velocity than my 338 Edge will safely and accurately provide, I'll lug my 338 Allen Mag along with me . I've yet to want more power than the 338AM can safely provide, so I'm OK for now.

Let me know what you think about the paper.

AJ
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