Powder density

I am shooting 59.0 gr. of Swiss 1-1/2 behind a 410-gr. bullet in my Browning .40/65. I bought a full case (25#) of powder all the same lot # and each jug has a different loft in the case. I weigh my charges to 1/10th gr. and all the cases are the same manufacturer. The volume in the case is anywhere between 1/4" and 3/16" between different lbs. of powder. My accuracy load is 59 gr. so I do not want to deviate. Should I be more concerned with weight or volume? I understand that Swiss does not like to be compressed, what should I do?

You will get different hight in the case when you drop the powder through the drop tube at different speeds.
Swiss will take different amounts of compression. I used .320" compression with a previous lot of swiss in my .44-90bn as well as .06" with good accuracy.
I also just got a new lot of swiss and it's a little lighter in weight of the same volume as the last lot.
Go with your weight and see what it does at the range.

All BP seems to like some level of compression - and there is a lot of difference between seating firmly and crushing into a pellet. Not sure if you are using a drop tube or settling the powder on a vibrator but typically a volume charge is considered "close enough" for most work. You could certainly weigh the load but still get volumetric differences due to variation in grain size.

I used to shoot BP in my 45-70 Sharps and used a volume dipper with a drop tube then I lightly compressed the load with a seating die. The bullets were then seated by hand.

I have scoop loaded a lot of stuff and most of the time it is good enough --however I can not get the same level of consistent velocity over the chronograph that I can get with carefully weighed charges - even there I dont study the fancy numbers just lookin for extreme spread in the single digit range for a ten shot string = cant get it with volume loading (my way and my powder - others might be different)

Weighing has always worked the best for me.

Kenny Wasserburger

Weight

were the cases all purchased at the same time ?

Cases all same lot #, Starline .45/70 reformed to .40/65 and trimmed to 2.130 for my Browning Rifle.

Years ago when I bought my first several cartride rifles (muzzle loaders only now) my mentor, the late Doug Knoell showed me how he did the loading and it was good enough for him to hold the world record for smallest group. He did say I had to experiment with powder loads, overall length and what wads to use. Here is what he said to do:
- Clean the cases, slightly bell the opening to let the bullet just slide in with slight finger pressure.
- Load the powder with a drop tube, starting with 62 grains working up to 70 grains.
- To figure overall length of case and bullet put some "flower foam" in a case, insert a bullet then load into the breech and close it up. There should be a few rifling marks on the soft lead bullet. Then measure the overall length and move bullet back about .002 to .003 from rifling.
- Try several different wads, Doug used milk carton and cut the wads with a TOTW wad press.
- Load 10 cases with powder, mark each case with load starting at 62 grains and compress the wad with a newspaper wad on the milk carton wad to get over all length. Note as powder load goes up, the amount of compressin will increase, no big deal. DO NOT COMPRESS WITH BULLET.
- Get your note book out and write up each load and then shoot at 100 yards or so. Measure the impact spread to get most accurate grouping.
- When you have the one that works best you can try other wads and other bullets.

It took me 6 months to get the most accurate loading set for the original Rolling Block with a Badger barrel. When I was done it could shoot .5 MOA at 300 yards with a 68 grains Goex FFG, Winchester primers, milk carton and news paper wads and a 540 grain bullet from TOTW and their Creedmoor mold using pure lead bullet. I sold my Rolling Block and two Sharps along with all my info and a bunch of loaded bullets to a fellow in Tenn.
John

Swiss 1-1/2 Granulation powder is quite chunky, so the concept that the same weight of powder with no two granules having the same shape are going to orientate them selves to settle at the same height in the cartridge case is ridiculous concept.

The mass weight of fuel provides the energy, heat and gas pressure to drive the bullet to your desired muzzle velocity.
That’s why cartridge cases got longer to put more fuel behind the bullet to make more velocity or to push a heavier bullet.
A heavier bullet makes more power, remember a firearm is a kinetic energy generator E=m vv.

Remember a firearm is a heat engine the hotter the gas the more it can expand just like in a steam engine cylinder turbine the bullet is the piston.

Your cartridge case dimensions and bullet seating depth limits your total fuel space, so to add more fuel to make more velocity we compress it down. It can be compressed because there is more space between the chunkier granules so it will compress easily. We also need to get back to the required volume of space under the bullet in order to get to our desired cartridge overall length (COL).

Remember the powder is energy in solid form, its fuel that we compress just to put more in the case just like a turbocharger or blower in a internal combustion engine pressurizing the fuel to get more in the cylinder.

So don’t worry about the initial powder column height as poured or dropped into the case.
Add fuel to get your desired MV with acceptable accuracy for your needs.

GET A chronograph AND GO BY VELOCITY velocity CHANGES WITH LOT NUMBER>> I HOLD ALL MY LOADS AT 1200FPs OR A LITTLE LESS WITH PURE LEAD IN A 45/70

Like anything else, there aren't a lot of shortcuts, and no one is going to be able to tell you exactly what your rifle will end up needing. I'd start with the same weight and then move it up or down a little in weight until you find the sweet spot.

Chris.