Duplex loads

[semtav]

Just curious, since I'm not contemplating doing any duplexing in the near future.

When you replace a certain percentage of BP with Smokeless, do you do it by weight or by volume?

If I remove 5 gr of BP and add 5 gr smokeless do I wind up with the same or different compression, or is it such a little amount, the size difference between the powders is irrelevant?

thanks
Brian

[August]

I do it by weight. The only published, laboratory loads I know of (Lyman Cast Handbook) are by weight.

My thinking about the compression goes like this.... We compress to make ignition more regular and to reduce fouling. Since duplexing makes ignition more regular and reduces fouling, compression becomes less critical. At least I think my thought is thinking in this way.

[twildman]

You certainly do not need much compression with a duplex load, but you need a little, lest the smokeless kicker charge migrate.

[NickSS]

I have loaded duplex loads in the past but do not do it any longer as I found better accuracy with straight black powder and the rifle is easier and quicker to clean. However, NRA long range rules allow duplex loads of up to 10% by weight and Canadian rules (if they have not changed them) allow up to 25% by weight. Personally I never went over 10%. I found that such powders as 4227, 4198 and H335 worked better than faster or slower powders I tried. You will also get higher velocities than with straight black. In fact that is why they allow it for 800, 900 and 1000 yard matches so that you can kick the 45-70 up to about 45-90 velocities. A good rule of thumb is that 1 gr of smokeless is equal to 3 gr of Black powder.

[BPCR Bill]

I've used duplex with the old Elephant brand BP with very good results. 60 grains of 2F and 5 grains of 4227 in my 45-70. That's by weight. I did not compress the load at all, just a drop tube. Since my old Elephant brand is used up I'm back to straight BP, either GOEX or Swiss. I think I have a can of KIK 2F around here somewhere that would perform better if duplexed.

Regards,
Bill

[Bent Ramrod]

Duplex loads get more practical (one might even say necessary) as the caliber gets smaller. I use duplex loads in my .32-40 rifle, but don't really need it for .45-70. I'm going to try it in my .40-90 because of the large amount of powder for the bore size, but a .40 caliber with a lighter powder charge shouldn't need it. I use 5 to 10% of the blackpowder charge and cut the blackpowder charge by the same amount. 4759 is the powder I use.

[semtav]

Thanks.
I may try it someday just to compare accuracy to certain loads, but for now BP is working fine.
Brian

[Oyeboten]

Link to some images of old Duplex Powder Throwers -

http://www.pbase.com/halp/schuetzen_measures

[BPCR Bill]

Those are some nice and desirable old powder measures. I saw an old Ideal #5 that a fellow shooter was actually using on his bench one day. He had paid around $600 for it.

Bill

[Oyeboten]

Yeowie!


Now that's dedication.

I'll guess he had a Rifle to match though...


That site which has the images of the old Duplex Chargers, had also many images of wonderful Old BP Rifles...