Not caliber specific. I load a lot of different calibers.

If I put together a max pressure load, with a longer COAL than a book states I would be under the max velocity and pressure, right?
Add more powder till I reach original velocity. I should still be under max ave pressure, right?
Now I get to add more powder for more velocity, but how much?
I've seen statistical data done on case head expansion, and primer flattening demonstrating neither are safe to use.
So do people just guess? Do people just set modest goals like "I'll just add enough to get an extra 100 fps"?
Thanks!

People think distance off lands not be like it is but it do!

It doesn't work that. way...Basically most cartridges have a max COAL(cartridge overall length), but most rifles are chambered with a longer throat then best for COAL...(less chance of too much pressure) If a person pushed coal out to bullet touching the lands and takes care, he can push up velocity by increasing powder charge...People do this safely by testing..by. normal reloading practices of raising powder charges by small amounts(typically .3 to .5 to as much as 1 grain depending on case volume).. while shooting over a chronograph and watching for pressure signs...he room for the extra powder is gained by the bullet being pulled outward with the longer COAL which makes more room in the case...

Notice how much of this bullet sticks into the case....
Attached File

Now compare these, the bullet on the right is a factory load at factory coal..if it had the same bullet as on the left the bullet would take up a lot of powder space to be at the same COAL... but due to the chamber being cut for the long bullets I can load long and gain back all that powder volume...In this case .350" longer COAL from factory coal of 3.600" to my loads coal of 3.950"
Attached File

Most long loads are more for accuracy tuning than chasing velocity.

Jamming into the lands will noticeably increase pressures.

IMHO.......you are making ALOT of generalizations that can’t be relied on.  
Yes..... moving the bullet out increases the internal volume you have in the case..... clearly.
What you find out doing so ......you’d have to test.....there is no set answer.  
IE.......Some bullets are designed (or end up) shooting better with “jump”, others are better closer to the lands.
IE.....By loading long, you may find the cartridges don’t fit in magazines.
IE.....What Ive noticed is powder charges vs velocity isn’t linear..... that is to say, more powder doesn’t automatically mean more velocity.

IMHO...... since I only have my chrono and my observations (of things like the primer flattening etc) those are what I use for deciding if I’ve gone too far.
But then I chase accuracy and not speed........

My personal experiences are with 80SMK’s loaded long for SR........

When running experiments like this, you watch every fired case for pressure signs, you keep track of temperature, and you perform measurements on the cases back at the reloading station.
Pressures signs tell you you have gone too far,
Blown primer pockets in less than 10 reload cycles tells you you have gone too far,
Shoulders blow more than 0.002 more than normal tells you you have gone too far,
Base blowouts more than 0.000,3 tells you you have gone too far.

5-to-10 shot group accuracy tells you if you have gone far enough or too far.

Please inform your friends at the range that you are using experimental loads so they can be at a safe distance when your gun goes boom.

When working this close to the sane pressure limits, you increase loading by very tiny increments, and weigh each charge, and measure each seated bullet.

Been pretty well answered in this thread.

In most cases I load long to reduce bullet jump.

Berger hybrid projectiles require a longer than SAAMI overall length due to their ogive placement.  Trying to load a 140 hybrid target to 2.80" (6.5CM) is a recipe for inaccuracy-the case neck mouth may very well be in front of the ogive.  Due to their length, you also lose case capacity.

Generally speaking, when loading long you need more grains of a given powder to bring velocity back to where it was when loaded shorter.  In some cases you can gain a little velocity, but that's not every time.  The only way to know is to test your loads and check for pressure signs.

You start by saying it doesn't work that way, then tell me how you did it the same way I said.

No plans to jam it.

What are you talking about?

Boom guns?
Insane pressures?
Large un weighed  powder charges?
Un measured bullet seating?
What post did you read?

Don't care about jumping Berger ogives.

Loading long to increase velocity is a normal practice. I am trying to understand how to do it safely. Western powders has a whole section for it in the .223 Rem. I in no way led anyone to believe I was going to be reckless. If you don't have the experience or the answers skip the question. Everyone is the shooting lifestyle is so arrogant.

@popnfresh help me out. Do you have any data do help out with a generalized question?

I know you load some stuff you figure out on your own with pressure trace.

Your post came across to me as you arbiltrarilly pick a longer coal and add some powder...And it doesn't work that way at all, you basically start over and work the whole load from scratch.. As for my rifle, It was a rebarrel, and while I seated longer on the other barrel, it was a factory cut chamber..this barrel had a chamber cut specifically for the bullet I shoot.. it involved  reworking my original load to the point it wasn't any better then the old load, which then involved a new powder and starting the whole process again..I finally got the results I was looking for after a bunch of rounds down the tube and a total revamp of my reloading techniques...

Sir if you only wanted Pop’s opinion and not anyone else’s......delete this and email him.
You seem upset that you get answers after posting a question on an open forum.
Otherwise several of us have explained how to experiment with this safely.......

At the end of the day, that's what loading longer than SAAMI is about.

If you want faster speeds, do load testing with different powder.  Same as if it was loaded shorter.

@Happy2shoot expand

I load all my precision stuff well over mag length specifically for max velocity potential(more room for powder, more velocity at the same pressure potentially).

My 18"(1:7 WC SPR bbl).223 AR with W748 and W760.
My 90smk is 2.580"@2600
My 80eld is 2.620"@2760

My 24" 6.5G AR(1:8 Brownells Grendel II chamber). With W748
My 147eld is 2.390"@2460
My 140hyb is 2.460"@2495
My 150smk is 2.525"@2420(shit)

My 19.75" .308 R700 (10 twist Bartlein) with W748 and W760
My 215hyb is 3.193"@2400
My 230otm is 3.245"@2370-2420
(W760 is heavily influenced by temp)

99% of the time I load .010" off the land and never move it. Some bullets don't allow for this as they won't have enough bearing surface in the neck.

If you don't have Quickload it makes it even trickier to start unless you are good with math to figure out load density.

Load density is important  to me, I don't want my light starting work up loads to be under75-80% load density. I want the powder to ignite properly.
I use Quickload to get the load density and input as exact numbers in every data point that I can measure.

The only thing I load "long" are my 223 loads for my bolt gun.  I do this because I have the throat and the magazine length for it.  Yeah I get more velocity from it, but this is a pretty normal practice and the the bullets i'm shooting are shaped for this practice.

I don't take my 6.5x47 and run it out to 2.900 just because it can fit it in an AW mag.   Seems like a pretty silly practice for most uses.

It can be fun to experiment and so some different things, but for me and many others it doesn't help solve any problems that exist in most cases.

I'm not sure even a 140 Hybrid would still be in the case with 2.9" 6.5x47.

Probably not, but that brings up another point.  Everything is specific to what you're trying to accomplish.

Thank you very much!

Oh no, you are into the 6.5 Grendel too!?
I just got a 12in pistol upper. Its fun.