A question of difference.

[Thumper]

Howdy guys,

Being that I just got some new rifles, well, bought, not yet received, I am trying to figure out what loads to make for them. I have a few reloading manuals Nosler 4, 5, and 6. I also have Sierra 5. My question is this, for a given load, the manuals are showing different min/max loads for essentially the same bullet. The caliber in question is 7mm Rem. Mag. Sierra lists 168gr SMK using RE19 min load of 59.5 and max of 64.3 and Nosler lists 160gr Accubond using RE19 min 57.5 and max of 61.5. I realize the Nosler bullet is slightly less, but if I go with the 175gr Nosler Partition Spitzer they list RE19 min 54.5 and max of 58.5. What gives? Being that I am going to use the Sierra SMK bullet, do I go with that recipe, or follow the Nosler one? I have used the Nosler one exclusively until I had bought the Sierra one. Any thoughts/ideas on this?

thanks,

jon.

[buffybuster]

When the data was collected for each of the loading manuals, the conditions are similar but not identical. There are a variety of factors that cause the differences in charge weights, velocities, pressures. Some of the differences could be: location and method the pressure transducer, instrumentation calibration, chamber differences, throat differences, barrel specifications/smoothness/twist/fouling/erosion, etc, lot-to-lot variation of powder, difference cases or lot-to-lot variation of cases, different primers, etc... there are many possible causes for the variation. Also the newer versions are usually a bit more conservative that the earlier versions. Some of this may be due to the desire to reduce liability but also it is due to better pressure measurement and some of the earlier loads that they thought were OK may have been on the higher side. Also, powders of the same name have evolved over time and their burnrates may be slightly different.

As for which manual to use, I would recommend that you use the most recent manual with the closest powder, case, bullet combination as possible. Different bullets of the same weight can have substantially different pressures due to bullet hardness, etc.

[Fjold]

Start at 59 grains and work your way up slowly unitl you get the performance that you want or reach maximum pressure in your gun.

[f4tweet]

Contact the powder manufacturer. The tech people are glad to help you.