% capacity versus efficiency

[ASCTLC]

Long story short, it has been determined that I have quite a bit of room to chose my bullet seating depth for my 30-06 using the 180 gr Partitions. I can't seat it far enough out to come anywhere close to the lands.

Now the question is this:
1) Does IMR4350 become more efficient as I reach 100% capacity by seating my bullet right at the level the powder fills the case or does a slight compression actually improve the efficiency of IMR4350?

The lower pressure specs for IMR4350 is one of the reasons I chose to try this powder as opposed to the majority of other powders.

2) Same question for W760?

3) Or do all powders universally gain efficiency as the case increases to capacity fill?

For the 180 gr Partition, I can go all the way from <100% capacity for the seated bullet if seating to meet the minimum caliber dia worth of seating in the neck all the way to a compressed load if I seat the bullet per some reloading manuals. (never seating any deeper than load books call for though)

Thanks,
Andy

 

[Kernel]

I don’t understand what you are asking. "Efficiency" is an abstract concept. There are many ways to define it. How do YOU define it?

Who cares what the efficiency is, any way. What maters is velocity and accuracy. I’d use the most inefficient powder available if it gave the highest velocity and best accuracy.

 

[ASCTLC]

Yeah, I thought about that after I posted the question. I've read a number of reloading manuals and thought I read about efficiency as it relates to case capacity somewhere but realized as you mention that it's kind of a deadend subject. It's there but pretty much meaningless for someone like me.

Andy

 

[Kernel]

Perhaps your question was really about Load Density. That's the ratio of the volume of powder to the volume of free space that's inside the case once the bullet is seated. In general, load densities for high performing loads will vary between about 85% and 105%. The later being compressed charges.

The Holy Grail of handloading is finding the "ideal" powder that will give the best accuracy, highest velocity, all at acceptable pressure AND have a load density somewhere in that 85-105% range.

In my view, in recent years, there seems to be a trend to higher load densities and slower powders. In particular, you see this in published loads used in high power competition. Slow powders and compressed charges. You would assume this is done for accuracy and is based on a lot of testing, but perhaps it's just popular fad. Group think. Shooter see, shooter do.

Did I touch on any of your questions in the proceeding ramblings?

 

[kelbro]

I get the best velocity and accuracy from loads that fill the case ~95%.

 

[Shoney]

Back when the 280 first came out, a lot of silhouette shooter selected it over the 7Mag. The reasoning was that the 280 uses quite a bit less powder, and delivers almost equal velocity, and does it with more accuracy. The term they used in the gun rags was that the 280 was more efficient and therefore more accurate.

Then people also started comparing lots of medium capacity cartridges to high capacity cased cartridges in the same caliber. I don't believe any of the arguments were strongly convincing.

In my experiences, many cartridges are more accurate with full cases and slower powders. That is not an absolute, but usually larger capacity cases will do better with a near full to full case. The 06 in bolt action is one of them.

IMR 4350 at or nealy at max is one of the best powders for bolt 06's. Max loads usually require filling by means of a long drop tube and/or with vibration in order to get it all in.

 

[ArchAngelCD]

IMO accuracy seems to improve the closer you get to 100% load density in most rifle cartridges.

For the 30-06 H4350 is my go-to powder for bolt action rifles. I achieve the best accuracy and highest velocities using that powder with 165/168gr and 175gr bullets.

 

[ASCTLC]

Kernel, Yes you touched on what I thought I was asking. And the others responding are too. I appreciate everyone remaining civil in their responses when I poorly word my question! I'm still learning.

I thought I was getting this impression from reading the reloading books but couldn't quite get my mind around it.

While I realize every rifle is different, if a loose general rule of thumb is powders tend to be more efficient as they reach 100% density, then starting from nothing like I am, my best chance of finding a great recipe is to start with a powder(s) that is near that 100% density.

Might be why I ended up with IMR4350 and W760 from my time lurking in all the different forums and reloading manuals (the one's I have).

 

[USSR]

ASCTLC,

If you want 100% load density, I would recommend RL22 powder for your 180gr bullets. You will get high velocity, yet you simply can't get enough RL22 in an '06 case to get into trouble.

Don

 

[ASCTLC]

Thanks USSR. RL22 seems to get a lot of good comments for this application.

 

[ArchAngelCD]

Might be why I ended up with IMR4350 and W760 from my time lurking in all the different forums and reloading manuals (the one's I have).

Just a side note. If you like W760 and have trouble finding it H414 is the same exact powder so you can substitute it for W760 if need be. BTW, W760/H414 is also a good powder choice for the 30-06. Don't leave out Varget either.