Loading Adjustments

[bayrunner]

Hey Guys_____ Just curios about ADJUSTMENTS in the loading process you guys might make IF at all! ! ! Example: Lets say your using” X “powder for two different bullet weights, lets say 250 gr. and 255grs. ,I take it the 255gr. bullet would Raise the pressure, please correct me if I’m wrong. So, if your loading manual ONLY has data for the lighter weight (250 gr.), and you want to load the heavier weight, would you use LESS grains? to compensate for the increase in pressure? ? ? It seems that I/m not in sink with the manual data I have, and I don’t want to waste all the bullets I have. .___THANKS BAYRUNNER

[PaulS]

In theory you are correct in assuming that you need to use less powder for a heavier bullet. The problem is that you may not want to use the same powder on that heavier bullet that you are using on a lighter bullet. It may be that the powder becomes unstable with bullets that heavy. Heavy bullets also use slower burning powders than lighter bullets. If the powder isn't listed for that weight bullet there may be a good reason for it. If you checked a few manuals and none of them list that powder then it probably should not be used. You can check with your bullet manufacturer, powder manufacturer, and if they can't give you the information you can call Sierra at their 800 number to get information that you should accept and follow. Sierra gives information on all kinds of loads with all different powders and bullets and if they say don't do it you can believe them. If they tell you that you can do it and give you a starting load USE IT! you can always slowly work your loads up but it is very hard to work a load down after you blow your gun up.

[Questor]

For safety's sake I like to stay as close to the book as possible.

In the case of cast handgun bullets I'll stick with common designs like the Keith bullets or target SWCs or Cast Performance big-meplat bullets. These vary some in weight, design, and hardness, but the load data seems to be pretty forgiving so long as I pick a bullet that is very similar to one I have data for.

One thing I find helpful is to use a Loadbooks USA book for my load data in, say, 44 magnum. Those books have load data for just about every bullet combination so I can always find something so close that I can be confident in the safety of the load.

As for specifically loading a 255 grain bullet with 250 grain data, I personally would be OK with that so long as the design and construction of the two bullets are very similar.

I am less flexible about varying jacketed bullets in high-pressure cartridges because some bullet designs look similar but are different enough to have significant pressure consequences if you use data not intended for them. For example, bullets that weigh the same, but one has a longer bearing surface than the one I have data for. I like to use the manufacturer's data.  I even use the same brand and model of primer as specified in the data for my rifle handloads. 

[cwlongshot]

Good advice from both previous posts.

I will add and agree with Questor, the 5 extra grains is trivial as long as seating depths are the same. if the amount of the bullet INSIDE the case changes that reduces the case volume and with the same amount of powder, raises the pressures. Raises them more than just the 5 grains additional weight.

 here is a good example: I have been loading 357Max lately. My favorite load is 26grs of 1680 and a 180 speer FP bullet. A max load, but entirely safe in my guns. I finally picked up some Speer 170 GDSP bullets. 10 grns lighter, so its safe to assume I could still use the 26 grs right? WRONG!!! The max listed was 23.5 grs!! A full 2.5 LESS. Why, well the bullet is designed for the 357 mag in a revolver and needs its bullets seated to a strict OAL length to fit in the cylinder. SO less case volume, even though the bullet is GDSP is 10grs lighter its using more of the cases power space.

ALWAYS start with 10% less powder then suggested and work up.