Bullet Seating Depth vs. Pressure Generated?

[tbetty]

Hey guys, so I'm going to get into reloading soon. I have a Lee manual on the way, and have been researching about techniques. However, I'm having trouble with determining seating depth of a load vs the pressure generated. NOTE: I am not making any loads yet, these questions are purely speculative.
Say, for example, I was working up a 6.5 Grendel load with a SAAMI maximum case overall length of 2.260" per the Nosler load data, and a minimum OAL of 2.135 per SAAMI specs. Suppose the powder charge was at 99% load density with the bullet at the max overall length.
-Is it safe to seat a bullet so the COAL is longer than the SAAMI specs in order to tune the cartridge to the rifle, for example to minimize jump to the lands?
-Would I be able to load more powder in due to the bullet being seated farther away and therefore less pressure in the cartridge?
-Would the bullet being seated farther away cause a decrease in pressure and therefore velocity?
-Is the minimum COAL the cutoff point for all loads, or only max loads?
Thanks guys, and remember that I am not working up any loads yet as I still have a lot of research to do!
Oh, and is there a calculator online or a formula to find out the pressure generated by the load?

[CS1983]

in order:

* yes; however, start with SAAMI and work up, looking for pressure signs along the way.
* yes; however, you need to do so incrementally to watch for pressure signs -- also, keep in mind max mag length unless single loading. You can get an idea of what others are doing, but again, work up and watch out.
* Yes, if you are just asking about two different seating depths with the same powder charge.
* Not sure what you mean here... are you asking if you can load shorter? If so, I'd advise against it as the chamber is meant to contain and direct the blast. If you shorten too much, you create a pressure problem. Can you go longer COAL than SAAMI? yes.

Check out some of Bryan Litz's articles: http://www.bergerbullets.com/bryan-litz-articles/

[20X11]

Oh, and is there a calculator online or a formula to find out the pressure generated by the load?
Quickload software will "model" all of these variables for you. Remember, you will still need to start low and work up loads, checking for pressure signs and validating with a chrono to make sure the load is safe in your particular gun.

[tbetty]

Thanks guys, and what are some pressure signs to look for? I've seen some about primers, are there any others?
And cavsct1983, I was asking about the minimum COAL as on the SAAMI website there is a maximum length and a minimum length. For the minimum, is that the deepest the bullet should be seated for all loads? Thanks!

[20X11]

http://www.massreloading.com/reading_pressure_signs.html

[XC700116]

With a rifle cartridge, if you load long enough that the bullet is actually touching or jammed into the rifling, pressure will go a LOT higher with the same powder charge as a load with a bit of jump, so when going longer, keep this in mind.

[earplug]

Google case head expansion. Its something you can measure for pressure.

[Delfuego]

Is this a bolt gun or AR? If it is an AR you likely will just load magazine length and not be near the lands.

If it is a bolt gun, I would locate the lands and seat you bullets using that knowledge. A lot of people will start 10-20 thousands away from the lands and fiddle with it until they have a good load. As XC said, if you "jam" your bullet into the lands you will get considerably more pressure.

[tbetty]

thanks for all the help guys!

[Zombie Steve]

Unfortunately, I think Lee has just about the most worthless manual out there. It never hurts to have another one, so I'd say Hornady, Speer or a Lyman manual would be worthwhile to have on hand. There's also the ABC's of Reloading.

When you're starting out, just try to match a load out of the book as closely as possible (same / similar bullet, same primer, same brass... ).

If you want, PM me an email address. I have a bunch of old manuals in PDF around here somewhere. The data might be outdated, different powders, etc, but the how-to section in the beginning hasn't changed much (if at all).