I have been feeding the power loads listed in the Lee and Lyman manuals into QL (yes, I know about not trusting it to give a max safe load) and have noticed that, depending upon the powder and weight, some loads indicate quantities in the box marked "Filling/L.R." which are in excess of 100%. According to the manual, that indicates a compressed charge.

Is that safe?

Does it affect the pressure or muzzle velocity to have the powder charge somewhat compressed?

What is a rule of thumb for the max usable compression - assuming it adversely affects performance? 10%? 5%? 20%? (I am being somewhat facetious about the 20%)

You folks have been doing this for a long while. Doubtless you have made up loads that compressed the powder charge to one degree or another. I am interested in a rule of thumb for a SAFE but usable charge. I will, of course, differ to your collective wisdom.

Thanks in advance.

Yes, compressed charges are OK as long as the loading manual indicates that is a compressed load. Don't know of any rule of thumb regarding useful percentage of compression. Stick with published data and you'll be fine.

There is no such rule, thumb or otherwise.

MY rule is if I have to compress a charge more than very slightly I need to switch to a faster burning powder.

Most of my loads are compressed, and some are highly compressed.

Many thanks to all.

Jim C. I shall try to find a powder for which I have data that offers acceptable muzzle velocity with minimal compression.