More powder with longer c.o.l.

[PaLuke]

My friend was telling me about the Berger manual stating that you can use more powder in a cartridge if you seat the bullet out further. Here is a copy of the piece.. I never knew this and have been reloading 25 or so years. Thanks for your input on the subject. PaLuke



Effects of Seating Depth / COAL on Pressure and Velocity
SAAMI COAL
Figure 1. When the bullet is seated farther out of the case, there is more volume available for powder. This enables the cartridge to generate higher muzzle velocity with the same pressure.
The primary effect of loading a cartridge long is that it leaves more internal volume inside the cartridge. This extra internal volume has a well known effect; for a given powder charge, there will be less pressure and less velocity produced because of the extra empty space. Another way to look at this is you have to use more powder to achieve the same pressure and velocity when the bullet is seated out long. In fact, the extra powder you can add to a cartridge with the bullet seated long will allow you to achieve greater velocity at the same pressure than a cartridge with a bullet seated short.
When you think about it, it makes good sense. After all, when you seat the bullet out longer and leave more internal case volume for powder, you're effectively making the cartridge into a bigger cartridge by increasing the size of the combustion chamber.

 

[SidecarFlip]

I posted that a month ago in a thread. My jury is out on it however but then I don't load Berger bullets. I just read it online on the Berger site.

 

[PaLuke]

Sidecarflip, I'll search it to see the responses. I've never came across any info like that and was just checking it out. Thanks for the time and response. PaLuke

 

[SidecarFlip]

No issue, I took it with a grain of salt. There is more going on inside a cartridge than just propellant burning. So I considered Berger's comments as loading beyond the maximimum proven load and candidly, I don't want to experiment even though modern receivers have vent holes for such 'experiments' on each side, it would still ruin the firearm.

If I had an old clunker, I might mount it in a Lead sled and use a string to pull the trigger to see what occured but thats about it for me. No old clunkers here, except me.

There is more discourse along with the powder versus jump theory about SAMMI specs and COAL, some of which I can accept, some of which I prefer not to.

I typically jump bullets but I've never increased the load past the loads listed in the respective bullet manufacturers books for the bullet I'm using. Again, I don't load Berger's, except maybe on the grill....oooops, thats burger, not berger...

 

[PaLuke]

Thanks again. I suggested to him to leave well enough alone.
He shoots a 270 and it groups sub moa with Hornady interlocks.
I'd personally be very leary going over max with any load. Why
chance it. Thanks again.

 

[mcharger440]

As long as you watch for signs who's to say what's safe I got all the way to 92gr of retumbo in my 338 ultra with 300gr bergers I ended up going back to 90.5gr for accuracy but even that is over book load it was loaded to a col of 4.088 with a custom throat so as for theory your correct however homework must be done and caution exercised

 

[FAL Shot]

You can increase powder load if you seat a bullet further out than book spec. Been doing this with 9mm Luger to get a powder load 20% or so over book, and 466 foot pounds of energy with a Hornady 115 XTP, which allows 1mm set forward of the bullet. On top of that, I use a popular .44 Magnum and 10mm Auto powder that compresses which slows the initial burn and reduces pressure. The +P 9mm Luger actually operates at 1000 PSI above 10mm Auto pressure. The Lee manual mentions this powder compression trick. Will not give load data as you MUST ascertain that your pistol can tolerate the forward seating and still have .030" bullet jump or therabouts.

You can decrease powder load by seating inward and/or using a magnum primer if you have been using a standard primer.

The point is that loose powder loads perform erratically so you need to get from a nearly full case to a somewhat compressed powder load for consistent performance. Somewhere in that range has always worked best for me.

 

[Mikecr]

What Berger said is not a rule, but a consideration among many.
Y'all are too hung up on books instead of real life results.
The people who puke load information into books don't have your chamber/barrel, or your lot of powder/primers/bullets, or your dies. So books are no more than a loose reference.

You have plenty of pressure signs before reaching any pressure 'problem', and you need to load for best results this side of any real problem. That means, forget the books and watch what's going on with YOUR gun and YOUR components.

What Berger has said here can be taken out of context, and the theory in it is still dependent on your cartridge, & chosen load components.
For instance, moving a bullet forward would not enable more of certain powders with certain cartridges, if doing so newly puts the bullet into the lands. Adding more of these powders here could produce actual pressure problems because of higher pressure needed for engraving(without a run).
However, accounting for extra capacity in long seating, more of a slower powder could be used to keep a good fill, and with increased velocity(depending on cartridge & barrel length), without pressure problems.
See, it's not a rule, but a consideration.