Inconsistent load data

[Roland Thunder]

I have noticed some inconsistencies in the load data provided by several load manuals as well as that provided on powder mfgrs web site.

Example:
Lymans 49 suggest for 45acp 3.5 gr of Bullseye for 185gr jacketed HP but only 3.4 gr of Bullseye for 200gr jacketed HP but 3.8 gr of Bullseye for 230gr TMJ.

It lists 4.4gr 231 but only 3.5gr HP38 for 185gr jacketed HP when they are supposedly the same powder.

It lists 4.4gr 231 OAL 1.175 for 185gr JHP and then jumps up to 5.5gr 231 OAL 1.178 for 200gr JHP and then only 5.2 gr 231 OAL 1.275 for 230gr FMJ

I realize the bullet types are different but I wouldn't think it would make that much difference. The OALs are different but in some case almost the same. In some cases the powder wt goes down as bullet wt goes up and in other cases the powder wt goes up as the bullet wt goes up.

On Alliants website, they list 5.7 gr Bullseye OAL 1.26 for Speer 230gr TJM RN but only 5.0 gr Bullseye OAL 1.20 230 gr Speer GDHP. That seems like quite a variance. I wouldn't think the bullet types would make that much difference and the OAL is only .06 difference. The 5.7gr Bullseye is quite a bit different than Lymans 5.2 for almost the same OAL (1.26 vs 1.275) for almost the same bullet type.

What's up with this, it's enough to make your head spin.

[jepp2]

I have noticed some inconsistencies in the load data provided by several load manuals as well as that provided on powder mfgrs web site.

Is this a surprise to you? Rather than call them inconsistencies, I think variables might be more accurate.

The differences you see can also be impacted by different powder lots, different testing equipment which can result in significantly variations in chamber volume, different brass casings, different primers, as you mention different bullets, different pressure monitoring equipment, and so on and so on.

That is just one of the reasons why folks will always suggest you check multiple sources before selecting your starting load. It is why you should always start near the minimum load (and I have seen the minimum load in one manual above the maximum load in another for seemingly the same load).

I personally find it challenging to pick a starting load when the pressure isn't provided. The Alliant website only lists a single powder loading. For the 9mm which is a high pressure round with a huge range of OAL (can be as short as 1.010" to the SAAMI max of 1.169" and as little as 0.020" can significantly spike pressure.

That is why reloading is an interesting hobby and why QuickLoad is so helpful.