I am interested if anybody has tried duplex loads i.e. some fast powder over the primer then the main charge. I have read this helps to reduce spread. With all the large calibers being discussed I am interested.

JeremyT, The book "SHOOTING THE BRITISH DOUBLE RIFLE" by Graeme Wright discusses this topic to some extent in regard to large capacity cases. I have quite a lot of personal experience with duplex loads, but this is a very DANGEROUS activity if one does not maintain certain rules to the letter. For this reason I will not give any of my duplex loads out, with out control of the loading process personally.

I would reccomend you get both copies of Mr Wright's book,(There is 1&2 editions) and read them very carefully, before attempting duplex loads. The books are available from HDS www.huntingtons.com

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..Mac >>>===(x)===>
also DUGABOY1
DUGABOY DESIGNS
Collector/trader of fine double rifles, and African wildlife art

JeremyT - Attempting to experiment with duplexed loads is much like playing rugby with a pocket full of nitro. The pressure spikes possible even with one or two grains of fast powder can exceed 70,000 CUP. Most folks that play with burn rates generally are not around long enough to write of their success.

IF there was a shortcut, or some miracle mix, or some magic formula, the powder companies would be all over it. The fact that duplexing is strongly admonished by ALL manufacturers is proof enough for me.

However, the laws of natural selection state that there is an element within all species which will test the laws of nature. These genetic wonders generally do not exist long enough to breed. Unfortunatly, man has altered the rules of nature and natural selection...

JeremyT, If I remember right Saeed loaded 1 gr of Bullseye (I think) just on top of the primer in his 700 H&H. He did this to help the large charges of powder ignite better in an effort to eliminate hangfires, if you can imagine a hangfire with a cartridge of this magnitude, it would without a doubt be a religeous experience!!. Other than that I have heard nothing advocating duplex loads, I for one wouldn't try it, it just isn't worth it.

Sooner

jeremy,
I load my 500 nitro with a duplex load.
After many load tests with our local powders like S365, 341 etc I was at a complete loss.
I had chatted to Graham Wright and Somchem and several other folks.
Most of the US powder companies I emailed did not even bother to reply. Hats off to Norma, they at least gave a few suggestions.
I could not get consistency or velocity and a clean burn with the S365. The inside of the case and the barrel were sooty. The S341 was showing signs of pressure before I could get to the required velocity.
As a last resort I tried duplex loads and it solved all my problems.
Consistency to within 20fps, clean burn and required velocity and no signs of pressure.
I use GS custom bullets seated flush onto the powder so there should be little or no migration of the powder. It is almost a compressed load.
I start with a tiny load of shotgun powder to augment the primer and fill the case with the required load of S365.

It is an unfortunate reality that obtaining the huge variety of powders available overseas is virtually impossible and we have to make do locally. I would dearly like to try Rel-15 but it is just not obtainable.

There is a practice locally of mixing fast and slow powders to get a medium burn, but that scares the bejabbers out of me and I am far from being convinced at the safety and viability of this practice.

I suggest you contact the Big Bore Association at the Aim show this weekend At Kyalami, we have tied into the Australian crowd so you will have a great amount of material and advice to work with.

Thanks for the replys. 500nitro will you be coming up for the show??

Jeremy,
I will be at the show saturday afternoon and possibly sunday morning. I will be around the Big Bore stand, GS custom, Rowland Ward/African Hunter and being persuaded by a very determined 10 year old that he "needs" a bow.
I will leave my cell phone # on a pvt email,
hope to see you there.