Why so much discrepancy?

[Spray-n-pray]

Why is there so much difference between different manaufacturers' reloading data? I have a Speer manual that calls for 5.1g of 231 for a 230g LRN bullet, and Hodgdon's calls for a maximum of 5.3g all other factors remaining constant. According to Speer, I am at minimum, but Hodgdon's says I am almost maxed out. Should I be concerned when I take my loads according to Speer to the range?

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[Spitpatch]

You have done well in consulting at least two load manuals. This is good practice for any handloading project, and usually I'll pull out every book I have.

Any number of reasons can account for variations in load data between books from different sources, and actually variations will occur from year to year even from the same source.

From the bullet manufacturers (Speer, Sierra, Nosler, etc, etc,), load data variations can be a result of their own bullet's design being different from a competitor, and therefore even within the same weight range, a different style of bullet will produce different pressures with the same powder charge. Nosler Partition bullets, and Barnes all-copper bullets are good examples of this.

Another factor in load data variation can result from the type of firearm used to develop the data: Most load books will say what gun they used for testing. Most load books end up using a different gun than their competitor. A certain firearm may develop higher pressure at a milder load than another firearm.

Using a different primer or different brass will also change pressures, and this might also explain why load data from one source is different from another. Again, most load books will tell you what brass and primer they used, and rarely are they identical to another book.

Updated test methods and results can bring changes in data as well: As an example, early .357 data is much hotter than current .357 data, almost from all sources. Methods of measuring pressure have improved over the years, and it was discovered that the old max loads were beyond safe in some firearms.

So, keeping in mind your good discovery, consult multiple sources for any project, start mild and work your way up. Be mindful that any change in component (primer, brass, bullet:even style only) requires starting over at the mild level. You can't have too many load books!

 

[toolfan]

Are the pressures for each load given?

Is this the online hodgdon manual? I've noticed that it tends to the conservative side compard to printed manuals...

 

[Gunner3456]

We can't measure the pressure in a given load. If one manufacturer's brass is thicker (the inside volume of the case is smaller) pressure will build faster and higher. Every manufacturer has different inside volumes - it may be that the base is thicker, or that the case walls are thicker or...

The only defense we have is:

1. Always use matched head stamps - same manufacturer of the brass. You can buy it that way on gunbroker.com for not too much of a premium. It will probably be once-fired indoor range pickup where the range requires that the ammo be bought from them, or a LEO range where they use the same brand. Since you can re-use it several times, the actual cost is low.

2. Always test the first few loads with a chronograph to see if your bullet speed matches factory ammo with the same bullet. Keep dialing it in until it does. Once it does, it's a good bet that you are close to factory pressure, and you know that the bullet will perform as designed when it contacts a BG.

3. This test also assures that you aren't making wimpy, useless loads or loads that are too hot for safety.

I consider This one a best buy. It has the ability to add remote equipment in case you are at a range and can't just walk out to it at will, and it has the ability to hook it to your laptop.

 

[PhysicsGuy]

2. Always test the first few loads with a chronograph to see if your bullet speed matches factory ammo with the same bullet. Keep dialing it in until it does. Once it does, it's a good bet that you are close to factory pressure, and you know that the bullet will perform as designed when it contacts a BG.

That assumption is pretty far from correct, you may be in the same ball park with using a similar burning powder to what the factory is using. But if the burn rate varies, your maximum pressure could be drastically different even though you're ending up with the same velocities.

 

[Gunner3456]

That assumption is pretty far from correct, you may be in the same ball park with using a similar burning powder to what the factory is using. But if the burn rate varies, your maximum pressure could be drastically different even though you're ending up with the same velocities.

Good point and I should have elaborated, although I have a tendency to elaborate too much.

You also have the min/max recommended powder charge from the powder manufacturer to keep you within safe guidelines.

So long as your powder charge is in a safe range per manufacturer, and your bullet speed is the same as factory ammo, you have a good load considering that we can't test everything. If you can't get your bullet speed right within the min/max charge recommendations, you need a different powder.

The real bummer is not testing at all and winding up with a wimpy load which won't get the job done per bullet design. Another bummer is using wildly varying cases and having varying speeds and a loss/variation of accuracy and performance.

 

[Spitpatch]

As to pressure listings, in my books, only Lyman does this, but my books are in need of an update. Speer 13 is the newest one I have. With new methods and ease of measuring pressure, perhaps some other books will start listing pressures for their loads.....BUT....

I take the Lyman pressure notations with a huge grain of salt for all the reasons mentioned previously about variables: the gun, the brass, the primer, the bullet, etc.

 

[2506]

I recall the Speer manuals indicating the max SAAMI pressure in the description of each caliber. Something along the lines of "maximum SAAMI pressure for this load is 58,000 and should not be exceeded." Doesn't tell you much, other than all the loads listed below the description will be below the max.