Load Data Disparity Between Sierra & Hodgdon

[steve4102]

Originally Posted by T. O'Heir

"...Others follow recipes..." Recipes for cooking are guide lines. Tell you what's in the dish, but you will not be damaged with 1/4 tsp more vanilla. Published reloading data is NOT a guideline.
Where you got the idea manuals are not science or engineering is curious to say the least. You think the ballistics engineers are alchemists?
Like Snyper says, manuals reflect the conditions on the day of the test, using the components listed and out of the rifle or universal receiver used. Variations by bullet makers is normal. Powder makers data is usually more reliable.
You'll note the Hodgdon max pressures for the 165 HDY GMX is a lot higher than the Speer SP with a fairly large OAL difference too.

I'm going to disagree with you here and say that Loading Data is NOT a recipe and is merely a set of guidelines. IMO if it were indeed a Recipe, then we would not see the differences from one manual to the next that we do.

As for your Bullet comparison, I again disagree.

First Hodgdon does not list a 165gr Speer bullet, they tested the GMX and the Sierra SPBT.
Next your "pressure" comparison is invalid. As the OP was referring to H-4350 I will stay with that powder comparison.

The Sierra 165gr bullet was tested using the older CUP units of measure, 49,400 CUP.
The Hornady GMX was tested using the new and improved PSI units of measure, 59,200 PSI.

As far as I know there is no mathematical formula to convert CUP to PSI and verse-visa. They are completely different units of measure and cannot be compared side-by-side.

Now if we switch over to IMR-4350 we can compare these two bullets as they were both tested in PSI.

Sierra 165gr SPBT = 57,600 PSI MAP.

Hornady 165gr GMX = 58,200 PSI MAP.

Virtually identical pressure listed for both.

[std7mag]

Naaaa, if you want a good fictional read, look at the Nosler manual...

[44 AMP]

There must be some "wiggle room" built in somewhere, either within the gun or the test results, about which you and I aren't privy.

You and I are already privy to all the wiggle room there needs to be.
"Work up loads in your own gun".

however, if I use a specific recipe and do everything properly and my gun blows up in my face then I sue the powder company, ..

From a strictly legal point of view, it doesn't matter what either say, what matters is what can be proved to a court's satisfaction.

Maybe you did everything "right. Can you prove it? (and you word isn't enough.)

Guns and ammo and all the things that they are made up of have tolerances. When things line up in just the right way, you get outside the zone of desired results. When you are dealing with pressures in the tens of thousands of pounds per square inch, that is not a good thing.

The people who test and publish data have absolutely no control over what you do with the data. No knowledge of the multitude of factors involved in your situation. NOTHING YOU DO IS THEIR FAULT!!!!

What I'm saying is, if I shoot a Remington 721 in 30-06 and they use an M-1 Garrand for their testing, am I supposed to buy an M-1 for shooting that recipe?

No, what you are supposed to do is understand that since you have different guns, that recipe could give a different result in your gun.

No one can predict exactly how much different the result will be. Starting below published data and working up, in small steps is recommended for safety. They all tell you this. WE all tell you this.

DO people ignore this, and simply load straight from the book (or screen, today?) Do some start with the listed MAX? YES, some people do. Some "get away with it" (meaning no physically dangerous results). Some do not.

Extreme differences in how individual guns handle a given load are rare, but they do happen. I'll give you a personal experience as an illustration of one wide variation. (not claiming anything more that that)

.308 Win, 150gr deer load, middle of the road powder charge (according to two different books). Feeds and extracts through my Remington like butter. Friend puts it in his Winchester. Feeds and fires fine, but he has to put the stock between his knees to get the leverage needed to open the bolt. No pressure signs on cases fired in either rifle. (that Winchester ran fine with factory, and loads developed for it, and a different Winchester, same model worked flawlessly with the same ammo that gave the hard bolt lift in the first Win.).

Things like this are why published data is a guideline, not a law.

[Bart B.]

RC20 asks just how much difference do I see between 4831 and 4895? 30-06 in this case.

Enough that tells me the slower powder doesn't produce the accuracy the faster one does with bullets of any weight until they're over 220 grains. And 4350 has only produced really good accuracy with bullet weights of 190 to 200 grains. Lighter ones are best with IMR4066 for 165 to 180 grains; 150's and lighter for 155 grain and under.

That aside, depending on how one tests a load for accuracy, any powder, bullet and charge weight may produce the tiniest few shot group and that's what most folks want to use; in spite of the fact that most of the time the smallest groups happen when all the variables cancel each other out. To heck with what the largest group sizes are; the one that uncover all the problems with ammo accuracy.

[RC20]

Its fun to think you got really good suddenly with a small group.

Reality rears its head on the next group of course, but for us amateurs it doesn't hurt to feel real good once in a while!