The UK's Finest Independent Forum for Shooters and Gun Owners. Est 2010.

I just heard about this stuff. Can someone please tell me if this stuff is close to Herco in terms of characteristics? I'm interested as when my dad gets his Anvil conversion, if its close we'll buy some from A and A in Skegness.

Load data is like rocky horse poo to find and even then it's for shotgun loads. I sometimes use it in my 44mag, a charge weight of 5.2 - 8.3gr works well with 200gr cast boolits, 7gr with a 240gr cast boolit gives 890fps from my Henry Big Boy.

Structurally however it's nothing like Herco. Herco is a large flake therefore not prone to falling through the cylinders primer pocket holes which is why it's recommended for nitro conversions using shotgun primers. GM3 is a very granular powder almost like very coarse sugar and the individual grains (looking at mine) would have no problem going through the primer hole.

If you need to use a flaky powder go with Vectan AS or A1.

mag41uk wrote:If you need to use a flaky powder go with Vectan AS or A1.

Who sells those brands then? I'm guessing they are comparable to herco?

Nearest powders to Herco are BlueDot and Unique in that order of preference.

I've not seen ANY load data from nitro conversion maufacturers using anything other than Herco, BlueDot or Unique, I'm sure there's a very good reason for this.

Vectan A0 appears to be similar to Herco.
If you get to Bisley I have some or try Clay and Game.

mag41uk wrote:Vectan A0 appears to be similar to Herco.
If you get to Bisley I have some or try Clay and Game.

Clay and game. I'll try them. Is there website clayandgame.co.uk or something like that? Then my dad will just have to figure out what the equivalent load is to Herco.

the reason A&A use GM3 is for cowboy shooting, they are only shooting their pistols 20ft, and quite often use black powder cylinders still, so 1.3cc of gm3 suits their needs

bradaz11 wrote:the reason A&A use GM3 is for cowboy shooting, they are only shooting their pistols 20ft, and quite often use black powder cylinders still, so 1.3cc of gm3 suits their needs

Oh thank you, 25 yds/m is what my dad wants. Do you happen to know what the equivalent measurements would be? I believe for if using blue dot they say use 5.7 grns, for Unique 4.1 grns and 5.0 grns of Herco. Any idea how many grns of Vectan AO and AS to use going on that guide?

Please be aware that GM3 is smaller than the shotgun primer flash hole and can leak out when filling the cylinders, use the powder that's recommended by the pistols manufacturer.