Bullet weight and different load data

[tipiguy]

I am looking to reload a 35 remington with 180 grain Hornady single shot pistol bullets.  I don't have a Hornady manual but I see that Sierra 180 grain FPJ has a max of 40.8 of H322, Speer 180 grains have a max of 38 grains of H322, and Hodgdon lists a 180 grain SPR FN with a max load of 35 grains of H322.

Why such a vast difference between loads for the same powder, same weight, and same .357 bullet?  Where should I even start with loading a 180 grain hornady in 35 Rem?

Thanks for your help.

tipiguy

[The Shrink]

tipiguy

Vast differences between bullets of the same weight is caused by different bullet shapes and how they engage the rifleing.  Differences between the same bullets:  look at the age of the manuals.  It is only recently that everybody has started using pressure barrels to measure the loads, and there were some changes due to that.  The other major variable is atmospheric pressure or the differening altitudes where the test firing was conducted.  

Others can probably give you a much more coherant answer than this, but I think I have the major variables involved.

[Ka6otm]

tipiguy,

I have the Hornady manual and here's what it says about the 180 grain spitzer in a pistol (contender or XP-100):

H322 starting load: 34.4 gr 2000 fps
H322 Maximum load: 38.6 gr 2200 fps

[John Traveler]

The Shrink is right.

Reloading manuals can give wide differences in loading data for apparently the same powder/primer/case/bullet weight combinations.

Much of this is due to as the Shrink indicated, variables including test conditions and standards used.

A lot of it is also a result of the ballistics test manufacturers going to peizoelectric pressure transducers and instrumentation from the much older copper crusher and tarage table system.

John