Manual discrepancies

Ed82

Ed82

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Need some advice from others here.
I've been reloading for the last 3 years and I bought the 9th edition of the Hornady manual right of the bat to use for loading .243 and .303B. Then I found the Hogdon website and started using their data as well and I noticed quickly that there were some differences between them for starting and max loads and for the estimated velocities.
Thent today I bought a box of 178gn A-max for my newish .308 but Hogdon doesn't have a slot for 178gn bullets, they have a slot for 175 and 180, which for IMR4064 they lost a start of 40.7 and a max of 45.2 . So I pulled out the Hornady manual, seeing as how I'm loading Hornady bullets and they lump the 178's and the 180's together but they list a starting load of 34gn and a max load of 41.3gn.

Now I know the Hogdon website doesn't specifically list the 178gn a-max, the 180gn they list for is a Speer soft point. But before you get all,"the bullets are different so the charge will be different" the Hornady manual lists 7 different bullets ranging from the 178gn BTHP to the 180 round nose giving the same data for all.

So anyway, what gives. I get some discrepancy between manuals but for one to give a max load that is only 6/10th higher than the starting load of the other book is just retarded. What are your guy's manuals giving for load data for this combo and what do you do when the books really disagree?
 
Use 180gr data in this case. As for different min and max they each used a different lot of powder, different rifle different lot of primers and bullets. Different elevation above sea level and probably different humidity and barometric pressure. Start low and work up.
 
medvedqc said:
amax is a longer and different bullet ... manual are conservative due to lawyer, do your works and find out what is safe for your rifle.
Click to expand...

This.
You look at older reloading manuals you will likely find higher loads.
Use the manuals, like all manuals, as a reference and a tool for your own judgement. Having a couple different books helps to find a middle ground as well.
 
Also, from one source to another, the barrel used to perform the chamber pressure tests is often different, which leads to different values and min/max charges. Even the choice of primer could have a small effect.
 
One point to ponder is that when data is given for 7 bullets the max charge must be safe with all of them. Hornady's data will be dumbed down to be safe with whichever of the seven generates the highest pressure.
 
Thanks guys. I've mostly been using the Hogdon data lately but to come across a difference of 4 grains between max charges kinda threw me enough that I figured I should double check some other sources. 4 grains is more like a change between powders than a change in chamber cut.

Cosmic, what is your lee manual listing as projected velocities? The Hornady max shows between 2400 and 2500 while the Hogdon website lists 2683 at 45.2 grains.
 
The manual data is collected in a lab using a SAAMI test barrel or a commercial rifle. Whatever it is, it is a different rifle than yours.

The manual is saying, in our rifle, we suggest you start with X and in our rifle we found Y was max.

I have a number of pairs (or triplets) of rifles that were made from consecutive barrels off the barrel machine. Each is quite different. In 308, I have a pair with 150fps difference in velocity with identical ammo.

Take the Start load and increase in say 0.3 gr increments (I make an initial batch of ammo in 5 round lots) and load from Start to MAx. I go a full gr past Max. Then shoot for group to see the area the rifle seems to like and also note where pressure signs start. First hint is often a little bit of resistance of lifting the bolt. Max in your rifle is about a full gr LESS than that load.

Load data is intended to get you into the right range of powder charges to test. It is not a set of loads to use. A Start load might be way over max in your rifle. I have seen that.
 
Each manual lists a starting load and a maximum load for rifle that they used and the specific components and lots of components that they used. When you consider just how much the dimensions in barrels and chambers can vary from rifle to rifle, and just how much components and even lots of components can vary, it's easy to understand just how much the starting and maximum loads can vary. And contrary to what some people assume, not all loads listed in the manuals will be safe in all firearms. That is why you start with a reduced load, and work up from there.
 
Nosler has online load data for reference as well.
308-Win-175gr-180gr-version-7-0.jpg
 
There is some good advice on here, I don't think I can improve on it. What I might be able to do is give you a different way to look at it. I have 4 or 5 fairly new reloading manuals, and about the same number of older ones. When it comes to working up a new load for a rifle, I check most of my manuals, some have suggested loads. Your rifle/barrel will be different from what they used, so will your powder lot number and primers. Read a bit and learn what pressure signs are. Ganderite has some pretty good advice.
 
Well I got out to shoot today. The 165's that I loaded for the ladder test were all over. Two tests with 10 shots each of 165gn SST and 165gn BTSP were both spread over 10.5 inches vertically. I thought it was just me the first time I tried them but I got the same results again today. I didn't really find any useful nodes between 42 and 46.5 grains on either test one possible node in the first 3 shots and maybe one starting at the high end.

The 178's were a different story all together. I loaded them in 1/2 grain steps starting at 41 and going up to 45.5. Bolt lift was fine all the way up but the cases stuck just a bit at 44, 45 and 45.5 Velocity was okay, about 2540fps at 43.5 grains. The beauty of this test was the 10 shots were within 6 inches and once I eliminate the 41 grain load and the 45 and 45.5 grain loads the other 7 shots were all writhin 1.75 inches vertically at 300m.

Thanks again for the advice guys
 
Last edited:
my Lyman manual lists 178gr a-max.
4064
start load 39.5gr, velocity 2373, pressure 43,600
max load 44.3gr, velocity 2669, pressure 61,100
hope this helps

180gr jacketed ballistic tip 4064
start load 38.5gr, velocity 2320, pressure 45,400
max load 42.5gr, velocity 2550, pressure 58,500
 
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