I contacted my local powder manufacturer and was advised to start with 36grs S335(similar to IMR3031) and a max of 39grs. I telephoned Magnum Magazine and spoke to a very experienced rifleman and he suggested a start load of 32grs same powder and a max of 36grs. So far I have loaded from 37.5grs to 38.5grs with no pressure signs. I really would like to download but not to the point of having to insert wads of Dacron or similar into the case. I should have asked him but it slipped my mind and I cant wait until tomorrow to fone him back as I have no signal or at best very bad signal where I will be for a while. I have just loaded 3 cases @ 32.5grs and three at 33.5grs. The cases looked around half full more or less. Should I have placed a filler over the lighter charge or not?
I am petrified of SEE and DETONATION. I do remember him saying that a REDUCED LOAD of 30gr will require a filler but not sure as to the slightly heavier loads of 32.5gr and 33.5gr, I forgot to ask. If any one can shed some light on this I would be most grateful.
Many thanks

Dunno anything aanout S335and I haven't loaded IMR3031 in over 50 years. However, 3031 is faster than either of the 4895s and they can be used for some nicely reduced load work. I thik 3031 or your similar powder should be OK at the loading level you're looking at. I don't know what bullet you are looking at but I do load 25.0 gr. of IMR4895 in the .308 Win. with a 150 gr. bullet as a practice load for my wife without a fillet. I use the same charge weight in the 30-06 in a cast bullet loading without problem although I do use a one grain tuft of dacron as a filler set lightly onto the powder to hold it next to the primer.
I do load for the 7x57 Mauser but my wotk has gone to the other direction, true and proper maximum loads rather than the very wimpy loads I get from the factories.
Best I can do for you without more details like bullet weight, ect.
As far as using a filler, try it both ways. that load is low enough that it won't make much difference in pressure with that powder and accuracy will be better on way or the other. your rifle will tell you which way it likes.
FWIW, SEE, PEP, or DDT, whichever was you want to name it is usually a Problem with slower burning powder like the 4350's, 4831's and slower. If your powder is in fact at or about the same burning rate as 3031, well I'm not seeingh a problem. I'd say the odds are quite slim and in your favor.
Paul B.

You're worrying over stuff that pertains to magnum cartridges, fire-forming for wildcat cartridges, experimental trials by qualified physicists/gunsmiths/mathematicians and military armorers. Do your own evaluation and then -- try S365 instead of S335.

No, you absolutely do not need fillers with a 7x57 using published data.

So I dont need a filler for the light 32.5grs load. At which point would a filler become nesessary? 30gr or lower? When the case is less than half full?

Bullet in question is a 175gr Hornady Interlock PSP.

If I wanted reduced loads in my 7x57 I would be using IMR 4198, SR4759, or Hodgdon's 60% IMR4895 data. But I'm guessing those powders aren't available in your neighborhood.

As Paul B said, you'll more than likely be OK. Good luck, and let us know how it shakes out.

I know of no documented instances (or even rumored instances, for that matter) of Secondary Explosion Effect with a powder as fast as IMR 3031. I realize that the Somchem product is not the "equivalent" of anything in the IMR line (and may even be a double-based nitroglycerin/nitrocellulose powder for all I know.) However, I wouldn't lose any sleep over accidentaly creating an SEE experience. I'm not sure why you prefer to shoot a load which is significantly underpowered for this round (most likely results in sooty cases and wide velocity swings), but if it performs as you desire there should be no safety concern.

(Almost forgot: Be sure to show this post to your health care providers and insurance company to illustrate that you were acting responsibly if and when the advice you've received above at no cost turns out to be worth what you paid for it. )

I had a SEE like experience with Accurate 2495 in a 1891 Argentine Mauser in 7.65. Increasing the load 3 grains and cleaning all the cosmoline out of the bolt corrected the problem.