Maximizing accuracy

[sailnaked]

In my quest to maximize accuracy and cartridge equality:
in looking at load data all over the place I have noticed some things:
A. on the same chart, different cup readings for the loads. Por Que?
I assume a full nearly full load will be more accurate than one with an air gap
if a barrel can handle a CUP of 7900 for one load why make one for the same bullet with only 6500?
max velocity is mostly better yes? faster to target, more stability....
B. different Initial velocity, with different powders why not maximize velocity at a certain CUP.

C. different books and sources have different load information for the same cartridge configuration.

I suspect that the numbers on the charts are assembled from different sources, and are not from the same trial or same rifle.

Is there a way to know what the maximum safe CUP is for loads with different powders?, do yall just keep increasing the load till you get ejection and primer deformation then back down a little? or get a full case?

to eliminate variables I try to fill my case to the bottom of the bullet without any compression or minimal.

 

[alamo5000]

Do you know what CUP is? As in actually.

 

[RegionRat]

A. on the same chart, different cup readings for the loads. Por Que?
I assume a full nearly full load will be more accurate than one with an air gap

Since we are making assumptions... I will assume by "cup readings" you mean copper units of pressure.
There are things about internal ballistics that have natural dispersion. Pressure readings are one of these things.

When you are seeing pressure being reported, try to keep a few things in mind.

One is that you are likely looking at an average. They took lots of readings and reported an average. What you must realize is that they are not reporting how many samples, and how wide was the ES of those readings (or the velocities). Was the reading from one test bbl, or several? All from one batch, or the cumulative average of several batches?

Some barrels are better than others. Not every test barrel gives the same pressure with ammo from the same batch.

Try not to get to down into the weeds and miss the big picture with load manuals. They rarely share the whole story.

Pressure readings are guidance, not a guarantee. You must test your context and proceed with caution. It should not be a surprise if your velocity doesn't match the load manual exactly, but you need the wisdom to stop and seek help when the difference is dangerous.

On full loads versus ones with space, assumptions are not worth the paper they are written upon. While this is general guidance to avoid noisy ignition, it is not a guarantee of success or failure if your load has a different fill value.

Your brass, chamber, and seating depth can cause a difference between your context and the load manual. Don't get too concerned.

Only a test in your specific context will determine if that space even matters. Is this good general guidance, yes, but it is also like the pressure discussion above where the specific context counts for more than the general advise.

Reports of Pet Loads from well established match rifle patterns are one thing, but don't expect to repeat the so called accuracy results in load manuals unless you are shooting the exact same barrel with the same chamber and barrel specs. Even then, you can still expect to need to adjust a half a grain up or down for your specific barrel and batch of components. Matching their case-fill volume is just guidance, not a guarantee.

Good Luck, YMMV

 

[Maurygold]

In my quest to maximize accuracy and cartridge equality:
in looking at load data all over the place I have noticed some things:
A. on the same chart, different cup readings for the loads. Por Que?
I assume a full nearly full load will be more accurate than one with an air gap
if a barrel can handle a CUP of 7900 for one load why make one for the same bullet with only 6500?
max velocity is mostly better yes? faster to target, more stability....
B. different Initial velocity, with different powders why not maximize velocity at a certain CUP.

C. different books and sources have different load information for the same cartridge configuration.

I suspect that the numbers on the charts are assembled from different sources, and are not from the same trial or same rifle.

Is there a way to know what the maximum safe CUP is for loads with different powders?, do yall just keep increasing the load till you get ejection and primer deformation then back down a little? or get a full case?

to eliminate variables I try to fill my case to the bottom of the bullet without any compression or minimal.

Neck tension and brass consistency is far more important than achieving a maximum pressure or case fill.

 

[alamo5000]

I assume a full nearly full load will be more accurate than one with an air gap

This is a false statement. Stop assuming this.

if a barrel can handle a CUP of 7900 for one load why make one for the same bullet with only 6500?
max velocity is mostly better yes? faster to target, more stability....

Again, max velocity is not your best option. Velocity and accuracy are two entirely different things. One is not derived from the other.

B. different Initial velocity, with different powders why not maximize velocity at a certain CUP.

Velocity doesn't come strictly from pressure. Especially now, powders are formulated to maximize certain bullet weight ranges. For example if loading 223, certain powders give better velocity and accuracy with 55 to 60 grain bullets, but others will be much better using 75 or 77 grain bullets. Just because it gives good velocity with a light bullet does not mean that same powder gives equal performance when using a heavy bullet.

How the pressure curve works and at which rate it gets there matters. A LOT.

If you put a shotgun powder in a rifle case until you get the pressure you want, odds are good that you will grenade the rifle. Again, just pressure alone is not the magic thing.

If you want a real life example, watch Kentucky Ballistics when his 50 cal blew up. He had tons of pressure.

Is there a way to know what the maximum safe CUP is for loads with different powders?,

Yes. It's called a reloading manual. Go beyond the published data at your own risk. That said some manuals are more conservative than others. If you want to go past published data, work up slowly.

do yall just keep increasing the load till you get ejection and primer deformation then back down a little? or get a full case?

The only time I've ever had an issue with case fill is when trying to work up specialty loads such as subsonic ammo and the problem wasn't too much pressure.

When reloading you ALWAYS need to watch for pressure signs at all stages.

 

[secondofangle2]

I wear a cup so if I get kicked, it doesn’t affect my load. Any my cup overfloweth

 

[straightshooter1]

In my quest to maximize accuracy and cartridge equality:
in looking at load data all over the place I have noticed some things:
A. on the same chart, different cup readings for the loads. Por Que?
I assume a full nearly full load will be more accurate than one with an air gap
if a barrel can handle a CUP of 7900 for one load why make one for the same bullet with only 6500?
max velocity is mostly better yes?

First. . . note a difference between "accuracy" and "precision":

I would say that a full or nearly full load tends to be more consistent than low fill loads (having to do with how the powder ignites uniformly as the powder lays in cartridge at the time of ignition. In a low fill case, the powder can lay differently depending on how the cartridge is handled upon chambering. A pretty full case load tends to produce better "precision".

faster to target, more stability....

Not necessarily. There's different things involved effecting stability of a projectile. In some cases, more velocity may not give the projectile enough time to stabilizes. Though, less flight time reduces the effect any wind will have on the projectile, particularly as distance increases.

B. different Initial velocity, with different powders why not maximize velocity at a certain CUP.

If you're after both accuracy and precision, then the focus should be on what you get on target. If you maximizing velocity, you're loading to the max pressure for the particular powder. That can be problematic if you find yourself shooting in conditions that will elevate the pressure or a condition in your chamber that can do that too . . . resulting in changing precision and even accuracy.

C. different books and sources have different load information for the same cartridge configuration.

I suspect that the numbers on the charts are assembled from different sources, and are not from the same trial or same rifle.

Yes.
They're often different because their own testing is dealing with variables that are different (e.g. same powder, but different burn rate as different lots burn at different rates; different chamber configurations used; different case volumes). This is why it's good to use those books as a guideline to get some idea where to start with a load and work up a good load that you put together with the components you happen to be using.

Is there a way to know what the maximum safe CUP is for loads with different powders?, do yall just keep increasing the load till you get ejection and primer deformation then back down a little? or get a full case?

When you choose a particular powder, and you want to work up a good load with as full a cartridge as possible, it's best to run a pressure latter to know where this particular lot of powder begins to have pressure signs for the projectile being used at a particular seating depth. Once you know where the max is for your cartridges in your particular gun, you can then start working up a safe load, starting low and working up to find a load that's accurate with precision.

to eliminate variables I try to fill my case to the bottom of the bullet without any compression or minimal.

You don't have to fill to exactly at the bottom of the bullet (100% fill). Having a fill as low as 95% can work just as well. The trick is finding a powder that can give you a good fill (like 95% or better), AND . . . will also be completely burned by the time the projectile leaves the muzzle.

 

[Doom]

Yes.
They're often different because their own testing is dealing with variables that are different (e.g. same powder, but different burn rate as different lots burn at different rates; different chamber configurations used; different case volumes). This is why it's good to use those books as a guideline to get some idea where to start with a load and work up a good load with put together for the components you happen to be using.

Also each references a maximum safe load, which may or may not be at maximum pressure. In fact if you read Hornady they will describe their method and it is likely the published load is below maximum because they chart velocity. IN many cases the load could be almost 50 or 100 fps below the velocity at maximum pressure.