Published Load Data - How Conservative is it?

[scoutm]

I know that published reloading data needs to be conservative to account for the vast quality and tolerance differences in rifles and components not to mention liability concerns but just how conservative are they?
I'm in the middle of load development for my first custom rifle and I'm right at or just above (depending on source) the published max load for my caliber/bullet/powder and showing no signs of pressure.
Being fairly new to reloading I'm very cautious about pushing the limits any further. However, I am looking for a bit more. I have found information in the various shooting forums including this one that suggest I can safely push the limit quite a bit. I've found numerous posts with powder charges in excess of 10% higher than the published max loads. I've even found some that are in excess of 15% higher.
Can the published load data really be that conservative? Are manufactures really leaving that much on the table? Or are there guys out there that are just willing to really pushe the limits?

 

[Lefty7mmstw]

From what I'm seeing in most calibers it isn't really that conservative unless you like beating stuff up. You can always go higher than SAAMI specs, but you will eventually pay the piper in reduced barrel life, beat up brass, stressed actions, etc.. Check out the pressure graphs I put up on the "4000 fps with a 140 in an stw" thread and compare to published data if you question it.

If you are looking for more like you said, either use a slower powder, a more efficient bullet, or re-chamber for a bigger caliber.

 

[Joe King]

Some manuals seem to be a bit conservative, others not so much. I believe though that for the most part if you go more than 2%over listed max your getting into that area that the disclaimer covers. And once at that point your not going to see much in improvements on performance, plus your being hard on your brass and rifle.

 

[old_heli_logger]

Listen to these guys, they know what they're talking about....and don't forget as the ambient temperature rises, so will your pressure (with most powders). It's best to error on the safe side…
Be careful and good luck!

 

[375fan]

Loads in manuals are meant to keep loads to SAAMI specs for the most part, taking into account the variances in firearms tolerances new and old. Yes, they (manual writers) have to worry about liability. For the newbie reloader the data in manuals is what they should stick with.

 

[boomtube]

"...but just how conservative are they?"

Last I over heard in the barbershop, 1.26% for handguns and 2.04% for rifles. ??

 

[D.ID]

That extra 50fps your yearning for aint worth it. Aint even worth killing a single piece of brass to find it, certainly not worth a rifle or the right hand side of your face. It won't change anything even way out there. If I am doing load development in hot summer which it is not (it's march everywhere) I load till the very first possible sign of pressure or max data, whichever comes first and work down from there if need be.. In mild weather, data is all you got.

 

[varmintH8R]

That extra 50fps your yearning for aint worth it. Aint even worth killing a single piece of brass to find it, certainly not worth a rifle or the right hand side of your face.

+1. Don't defy real data based on an assumption that the manual writers are incorporating a safety factor.

 

[Bart B]

In comparing some "printed" load data's to what SAAMI lists for their specs reveals a lot of differences. Therefore, many of those developing that "printed" load data are measuring both pressure and velocity with a rubber tool.

Few sources of published load data uses SAAMI spec barrels and pressure/velocity measuring systems.

And the biggest variable is the pressure measuring system. Most of it uses the least accurate system of all; the human eye looking at fired cases with all sorts of structural varaibles they don't know about and the human brain evaluating what it sees. To say nothing about the differences in their barrel compared to that used by the published load source.

In second place of variables is the velocity measuring system. A given load will easily have a 100 fps spread across different barrels of the same length. Same spread across several people holding the same rifle to their shoulder shooting the same load.

 

[CogburnR]

I've had a few rifles where the printed max loads could not be safely approached.

Some of the old manuals have loads that are plain hot.

If your velocity is approaching book velocity your pressure is also.

Barrels that are longer, tighter bores, have longer throats, or have different rifling may be faster.

Barrels that are shorter, looser or have smaller chambers and shorter throats are slower.

What that means is that you might well be able to exceed individual loads from a manual due to the characteristics of your rifle but, it won't be a lot, and your loads might very well be too hot in another rifle.

Pressure signs may not show up until well past saami spec..

 

[scoutm]

Thanks for all the comments.

At the end of the day it appears that I should really just quit looking for data on the web and stick with what's in the books.

 

[nonnieselman]

Thanks for all the comments.

At the end of the day it appears that I should really just quit looking for data on the web and stick with what's in the books.

yep!
Just tinker with the load till you like the accuracy..

Most guys will load in ~.5 increments till they see pressure signs.. then you know your limits and how close you are to those limits.
Majority of my rifles are most accurate well below those max pressure signs.

 

[Truc]

I worked up some loads for a 7 SAUM and after reaching the max and backed down, I got the Berger reloading book and their Max load was just .3 gr more than what I ended up using as my load. Some may be more accurate than others