Second look at load density

[stubbicatt]

Good morning.

When I was a tenderfoot in hand loading, I remember reading about load density. The proposition that a case very nearly filled with powder is more likely to bring uniform burn than a case only half filled with powder. Uniform burn, in turn, leads to better accuracy. Ok. File that in the "need to know" drawer and return to it when conducting load development.

Fast forward many years. These days I'm loading cast bullets in 32-40 and 30-30. Both of my rifles give me really good results with volumetrically small charges of IMR 4227. Like right at a MOA, sometimes a little bit less. Sometimes worse. Heck, I've read of folks using wads, toilet paper, dacron, and other methods to assure that these smaller powder charges remain close to the primer, in effort to achieve more consistent loads. I haven't tried these things, fearing a ringed chamber or worse.

I haven't futzed about in these cartridges with any bulky or slower powders like 4831 or anything like that, so I cannot comment. Maybe they will perform better. I can't say. I can say these low density loads shoot as accurately as I can hold these guns.

So too I cannot really reasonably explain the performance of these low velocity, low volumetric density, loads. I guess all I am able to take away from this puzzlement is high density loads are better, except when they aren't.

[JSnover]

If you're asking why these low-density loads work when they shouldn't, some powders are not as position-sensitive as others. Unique and SR4759 worked well for me when I loaded light for my 45-70. Nothing in the case but powder and a 405 grain boolit.

[fecmech]

How does a 30-30 case with 5 grs of Bullseye sound for load density? In my Savage 340 I get 1140 fps with lyman 130 gr pb bullet. The ES (for 10 shots) is 19 fps and SD of 9 fps. Group shown is 10 shots@100yds, one slipped out the bottom. No fillers and large pistol primer.

[TXGunNut]

With medium and slow powders the "load density" principle is often useful, often a powder that comes closest to 100% density works best. I think this principle is especially true with j-words. Many boolits seem especially happy with faster powders that are not position-sensitive. I must admit the more I know about powders the less I know about powders. Most are made with very basic ingredients but the variations and characteristics are mind-boggling.

[35 shooter]

I think muzzle and chamber pressures are a major player especially with cast boolits.
The faster powders can and do shoot great regardless of load density..to a certain point (speed), then accuracy goes south in a hurry.

At that point, switching to a slower(higher load density) powder can restore the same accuracy at a faster speed.

12 gr. of unique in my whelen cases isn't very much powder at all, yet will easily shoot an inch or better @ 100 yds with a 280 gr. rn @ 1275 fps. Any more than 12 gr. and accuracy is gone.
A switch to slower 4759 gives more case fill and gets me to 1800 fps. with the same accuracy.
Then a switch to slower imr 4350 and close to case fill gets 2200 fps. and accuracy is restored with the same boolit.

I'm working with aa4350 now and am just before compression with a 230 gr. boolit and should be between 2400 and 2500 fps. with good accuracy...still tweaking this load though.

Lol, after all the load developement, and playing with slow powders and load density i've done in the whelen trying to shoot faster accurately though, i could have killed every deer i've shot with cast boolits so far with that 12 gr. unique and 280 gr. boolit load with a soft alloy.
I rarely shoot a deer over 60yds. in the thick woods i hunt.

Btw, i haven't found a need for a filler with that unique load and like you, i prefer not to use them if possible.