Book vs Hodgdon online data

[cs86]

The other day I wanted to load some 308 win cases with 165gr SST bullets for testing accuracy. I didn't have my book with me because I forgot it at another place. So I got on my phone and looked up data on the Hodgdon site using Varget powder. They listed 42gr starting and maxed at 46gr compressed. I decided to load them, 5 rounds each, starting with 42gr and working up in .5gr increments. When I got to 45.5gr I decided not to go any higher because it was already making the powder crunch when seating the bullet. All were seated at 2.8 COL.

When I got my book later on I noticed the Hornady book was a lot different in where it started and stopped with the load. If I remember right It started at something like 38gr and maxed at 44gr. Why is there such a spread? I guess I'll have to watch for pressure signs when stepping up the load when I go out and test them. I'm guessing my loads are going to be pretty heavy on the recoil.

[tazman]

Hornady may have used different brass and primers than the Hodgdon testers did. They may also have used a different gun with a slightly different sized chamber. All these things make a difference, particularly at the high pressure end of things.

While I haven't loaded a lot of rifle using Hodgdon's data, their pistol data has been right on for me.

[bhn22]

When I use really bulky loads that fill the case, I'll often take the filled case, put my finger over the case mouth and shake it a bit to settle the powder. Powder is measured by weight, not bulk (in most cases) so this often helps, especially with extruded powders. Then seat the bullet normally.

[Blackwater]

There are many variables at work when determining max. loads. Some brass is thicker, and therefore is heavier and has less internal volume. Case heads may be thicker, also reducing case capacity. Chamber throats in barrels vary as well. Some have longer throats, which allow the initial expansion of gasses on ignition "spread out" more, thus lowering peak pressures, which determine max. loads, and ONLY occur at the brief moment just after ignition when the bullet hits and starts into the rifling. Once the bullet is "on its way" so to speak in the rifling, the powder gasses are expanding and doing it in an ever increasing space, thereby lowering pressures as the bullet progresses down the barrel. Ever noticed how light sporter barrels are still heavy at the chamber area? That's the reason. More metal HAS to be where the pressures are greatest (at and near the breach), and can be thinner where pressures have dropped to lesser levels. Very simple.

Then there are the small but real and rarely but occasionally significant differences in lots of powder tested, primers used (brissance, or how "hot" the primers used are with that powder). Hotter primers almost universally give higher pressures, but don't always yield higher velocities. However, they may give much improved ignition with some powders, like ball powders in general, and thus, better accuracy.

All these things work together to make reloading an endeavor where our own personal testing and trials are effectively required to determine what's max., best, or optimum in our individual guns. Guns are individuals, just like we humans are. No matter how great our technology gets, there is always SOME degree of variation. If we desired perfection, it would take so very much extra effort that our guns would cost many times more than they already do. As it is, they're easily "close enough" that anyone with a modicum of good judgment should have no trouble finding and loading really good ammo. Yet, there are always those among us who seem to be able to tear up anvils with rubber hammers, but they're very few, and if they blow themselves up .... well, it's just "nature" at work is all I've been able to figure. The more we keep trying to protect people from their own selves, the more we make them challenge our ability, and even sometimes our willingness, to do so. Funny how that works, ain't it? So, we live with very highly reasonable tolerances and resulting variations, and adjust accordingly to "customize" our loads for best performance in our guns. I once had an '06 and my loads that performed in a stellar fashion in it wouldn't fit a friend's '06 when he forgot his ammo one day. They were seated too long for his short throated chamber, and he couldn't close the bolt on a round. That sadly killed that hunting trip. Haven't run into that but once in my whole lifetime, though, so it's extremely rare, but it CAN happen on very rare occasions. Then too, it's part of the reason we reload: to find or custom tune our loads to our particular barrels and bedding, so we can punch those itty bitty groups out on paper, and hit at very long range, and do it with confidence and repeatability. It's dealing with the variables that makes reloading so very satisfying. Think about it. What would it be like if all we did in reloading was just go though the motions to get the same exact thing that the factories make? That'd get awfully boring, and be rather pointless, wouldn't it? It's always the CHALLENGE that makes things worth while. Lack of a good and worthy challenge has a name. It's called "boredom."

[scottfire1957]

So, you have only the Hornady manual, and you've never cross referenced data in that with other sources, until now.

[dragon813gt]

Did Hodgdon have a load listed for that exact bullet? I defer to Hornady's manual when using their bullets. I also look through all of their manuals since I own them. They have changed over the years.

[fredj338]

Something all new reloaders have to learn, data sources, whether manuals or online, are a guide, not a bible. Every test platform & condition is diff, so the data will be diff. Your gun will be diff than the test source platform, adding yet another variable. So I use avg data from 3 vetted sources when working up a new load. Start @ avg midrange & work up. I have never seen the point of using starting data.