Why the Load Difference?

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I'm loading up some 357 sig ammo with 8.5gr of N105 and 124gr FN Xtreme bullets but I just ordered some 124gr JHP bullets from Xtreme and was looking at the data from Sierra and also Lymans and they are both the same except for the powder loads. The Sierra book says 8.7gr to 10.5gr max I believe but the Lyman book says 10.1gr to 11.3gr max. Now the Sierra book says they are using their bullet but Lyman does not mention which they are using. I was wondering if anyone would know why such a big difference in loads especially one that almost starts with a min load which is the max load of the other, just doesn't sound right.

 

[Ringostar]

I used to load 357 Sig. It might have something to do with varying bullet design. They can be loaded to different seating depths. The seating depth can make a big change on internal case volume, when working with a small case capacity to start with. If you have an accurate chronograph, you can try loads to get the desired velocity.

 

[CatShooter]

I was wondering if anyone would know why such a big difference in loads especially one that almost starts with a min load which is the max load of the other, just doesn't sound right.

Loading is not an absolute science...

The barrel diameters and finish were not the same.
The chambers were not the same.
The throats were not the same.
The method of documenting pressures were not the same.
And the operators were not the same.

So why should the loads be the same.

 

[Thumb]

Loading is not an absolute science...

The barrel diameters and finish were not the same.
The chambers were not the same.
The throats were not the same.
The method of documenting pressures were not the same.
And the operators were not the same.

So why should the loads be the same.

Yes, all those variances do make a difference and I would think that the actual seating of the bullet would cause differences in pressures. I will measure the HP bullets when they get here tomorrow and see if they are longer than the JFP bullets.