So I was looking at a Hornady manual in Gander Mountain today and found the .308 section. They lump all their 165-168gr bullets together. They give a range of 32.6-44 grains of Varget for various velocities.

When I got home I looked at my Lyman manual and for a 165grain partition it lists 41-46 grains.

What gives with the differences in max loads? I guess I'm failing to see how a bullet of the same weight could alter the pressure of the round. Its very possible that I'm wrong here thus the question.

If pressure varies based on bullet, with weight be equal can someone please explain to me how?

Thanks

Doc.

The reason manuals differ in max recommendations is the same reason they say start low and work up in your gun. All reloading manual data is just a guideline to get you started safely.There are multiple variables beyond bullet weight that can change pressures. Softer vs harder jackets or bullet bearing surface can change pressures from one bullet to another of same weight. Under most circumstances these variances are not enough to cause major issues but of course manufacturers are going to err on the cautious side.
I have one rifle that I load 5 grains over the highest max I have seen published. I did not start out to go that high but kept working up to what is perfectly safe in my gun.

1. Different firearms used for testing.
2. Different bullets with different bearing surfaces and jackets.
3. Hornady manual seems pretty conservative. imho

I thought about that so I was pretty surprised that they grouped all their 165-168gr .30 cal bullets together

It could explain the lower max load I'm the hornady book. They are giving loads for a range od bullets instead of just one.

4. Different lawyers

I have a lot of different manuals and they all disagree on max loads. I have found that Hornady is conservative and Sierra isn't.

The Lee manual has a 1 grain factor that I check but don't really know how accurate it is.

But, Dan may be right. If I look at the same bullet on a 20 year old manual and a new one, the newer ones are generally more conservative.

Buy, collect, and save as many manuals as possible. Understand that max loads can vary for the reasons other posters have written. If you take an average of all your manuals' loads, you will have a general idea of where your load is going to be.

From there, it's time to rely on your chronograph. Let's say that you are looking for a top load for the 165 NPT for your .30-06. You should be able to achieve around 2800-2900 fps. Shooting over your chrono, carefully begin working up toward that velocity, while carefully watching for signs of high pressure. If you are happy with your accuracy when you arrive at the published velocity--assuming normal pressure signs--then you've found your pet load.

More and more, reloaders are paying as much attention to velocity as they are to "book" loads, understanding that the loads printed in the manuals are suggestions, rather than biblical rote. Just use some common sense as you move up the velocity scale. And, if you don't have a chronograph, get your significant other to give you a ProChrono for Christmas.

Reloading without a chronograph is like a blind man in a dark room searching for a black hat that isn't even there.

I just had to check. I have 35 manuals/booklets dating back to Col. Townsend Whelen in 1957. Heck, there may be another one or 2 out in my shop. If/when I buy a rifle with a different caliber, I try to get a one caliber booklet. I don't try to collect these things. They are just here.

I like the blind man in the dark room saying. Never heard that one before.