404 Jeff - looking for some clarification regarding loading 400 grain Northfork SS bullets

[Angelo_orygun]

I think it doesn't matter much. No DG will ever know the difference. Low SD and ES are important for 800 yard shots. Nice to have in a big bore, but not necessary.

This exactly! Was thinking that after my previous reply!

 

[cajunchefray]

I have never used filler. Sorry, no idea, other than that's why it's used. How much to use with what kind of powder for which cartridge...beyond my kin.

I have used "filler", backer foam rod, cut to length so it slightly compresses the powder column, in 450/400 NE and 416 Rem Mag.
Available at hardware stores in 1/2" and 5/8" diameter. Open cell foam, very similar to Kynoch wads used to reload the big Nitro Express cartridges, to take up space with modern powders.
I found this information from Butch Searcy, Grame Wright, and pressure velocity tested by @michael458, he compared various fillers, Dacron, open cell foam, etc.

The backer foam rod yielded more consistent pressure, no debris in the barrel, consistent ignition. The powder column is firm against the primer with no airspace. Easy to use in reloading.
The wads improved my groups in my 450/400 Nitro, I think due to consistent ignition, powder burns easily every time.

I have done some work with Puff-Lon filler in 350 grain loads in a 458 Win Mag, seems promising, but need more testing. Puff-Lon is a buffering powder, designed for shotshell reloading, but also recommended as a filler for rifle loads, inert, and claimed to help consistent ignition.
I liked it with 350 grain Hornady FP, and 5744 in reduced loads in the 458 Win Mag.

Anyone else have experience with Puff Lon in the big bores?