Written by Sierra Bullets Ballistic Technician Philip Mahin
This may be an old hat to some of the more seasoned reloaders but it is worth discussing again. A lot of new reloaders have asked about the differences between manuals and what data is correct. The answer is very specific to the set of components that a single reloader is using at the time.
If we look at the 30-06 cartridge and 150 gr bullets, we can see a lot of differences even referencing to a single powder like H4350. A 150 grain is a 150 grain is a 150 grain, right? No. Even from our own lineup listed above, you can see several different designs; some have a lot of bearing surface compared to others that don’t. With all other things equal, a bullet with more bearing surface will create more friction therefore more pressure. Since it has the longest bearing surface, we used our #2135 Round Nose bullet to develop the 150 gr load data in the 30-06 cartridge. When you change bullet makers, you’re not only changing the bearing surface length but the makeup of the jacket. This can make a difference in a top end by itself but when you add into the equation the different primers, cases and especially firearms you can see a 3.5 grain top end difference from manual to manual easily. If the other bullet doesn’t have a jacket at all or only has a copper wash on it, that can change top ends also or even what powder is recommended to use with it.
Because of the subtle (and sometimes not-so-subtle) changes in bullets, we always recommend referencing data from the bullet manufacturer, just like we do when someone calls looking for us to quote something. We like to be specific and know at least what brand of bullet a caller is using so we can go to that brand of manual; we do keep other manual brands on hand to reference, as well as the Sierra manual. The reality is the reloader needs to realize that they have a completely new set of components and their top ends will change from ours or others data. That’s why we recommend beginning at the listed start load (from the appropriate manual) and working up in an incremental value appropriate to the cartridge. This will give a shooter room to work up without just jumping on pressure signs immediately.
The firearm used can change the top ends a lot. Let’s look at the 44 Magnum cartridge from a lever action as well as a revolver. Just from our manual alone, this cartridge using our #8610 240gr Jacketed Hollow Cavity and using Winchester 296 powder gave a top end of 24 grains in the lever action. That same powder in the revolver gave a top end load of 24.7 grains so almost a 3% gain. The #9 powder from Accurate went from 20.4 grains in the rifle to 21.4 grains in the revolver so almost a 5% gain. Both of these sets of data resulted in a maximum pressure but it took different amounts to get there. This comes from the rifle using all the pressure to push the bullet out of the barrel and the revolver having a gap between the cylinder and the forcing cone bleeding pressure as it tries to do the same. Going to another brand of data can show even more change but when it all boils down, a top end load will be determined by the reloader seeing pressure signs using his or her own components.
I’ve heard it said that even though someone uses 2 ¼ cups of flour and someone else may use 2 1/3 cups of flour in their recipe; they still make a darn good chocolate chip cookie! The same thing can be said about reloading recipes. As long as the person shooting them is getting accuracy without seeing pressure signs doing it, that is what matters. You can get there by working up from a safe start load – so have fun shooting!
If you have any questions about reloading data from a Sierra Bullets reloading manual or any other please don’t hesitate to contact us at 1-800-223-8799 or by email at firstname.lastname@example.org.