black on black duplex

[hiram]

I've read that some shooters use 3f in i.e., 45-70 because it burns cleaner than 2f, and for them, it is accurate.

Further reading indicates that a small charge of smokeless under 2f leaves a clean barrel. This is what most people consider a duplex load.

Has anyone ever experimaented with a small charge of 3f under 2f, to make a black on black duplex load? Will the powder burn cleaner than with using only 2f? What other info is floating around?

Thanks

[Jon K]

Is this something you really need to do, or just not happy with the perfomance?

If you are going to duplex the load try 4F under the slower powder. Usually the duplex is used for more velocity. Reduce your regular load 10% and replace that 10% with the Black or Smokeless to duplex.

Try to find a load that will work, rather than duplex. Keep it Simple.................

Jon
:castmine:

[Baron von Trollwhack]

I've duplexed with smokeless and ffg or fg but not with fffg as the main charge. I did it as a power factor not for shooting cleaner, whatever that is. I figured that up to 10 grains of Re-7, Imr-4227, ww-296, Imr 4198, was worth about 3 grains of fffg equivalent per grain smokeless. This only in a B-78, M-94, 336, or the like. Not in a trapdoor. These kinds of loads go back to the first use of smokeless, and data is available from Sharpe, old Lyman manuals, and even Ken Waters in the 50-70/'63 Sharps. BvT

[Dale53]

Before I was "forced" to learn how to manage black powder in a black powder cartridge rifle (when I graduated to NRA regulated silhouette matches) I shot a truck load of duplex loads. I used 10% smokeless to 90% black by weight using RL-7 for the smokeless. I would first develop a load using straight black - for instance if the black load in the 45/70 was 65 grains, I would subtract 10% of the black by weight (6.5 grs) then use 6.5 grs of RL-7. RL-7 was chosen specifically for its combination of burning rate and small grains that measured well.

It was as accurate as straight black and didn't require the use of a blow tube to keep the powder moist. You could literally shoot all day without the necessity of cleaning or wiping. The case was full (I actually used a compressed charge) and there was NO danger of SEE. Further, the performance was excellent regarding chronographed data with low Extreme Spreads and Standard Deviation. In fact, they were DANDY loads by any standard. It makes an excellent hunting load, also as fouling never raises its head.

Duplex loads have been "damned" by a lot of shooters who either have a political agenda (traditionalists) or are without knowledge. Canadian long range shooters have been using duplex loads up to 25% of smokeless for many years without problems.

I only use strong action guns so I am not concerned about pressure problems as they are WELL below reasonable smokeless loads. The Lyman cast bullet manual has actual pressure data, if anyone is interested, to back up my statements.

Keep in mind that there are those who could screw up a granite boulder and ALL loading requires a bit of knowledge and a cup of common sense...

Dale53

[hiram]

I am happy with the performance of my load---Lee 500 3r, 60.3 2f, milk container wad. I'm just looking for a cleaner burn. Duplex loads with smokeless are not allowed at my club's matches.

[NickSS]

I experimented with both mixing 3F and 3F powder in various combinations as well as putting a booster charge of 4F under the main charge. They seamed to burn a little cleaner than standard loads but not a clean as ones using smokeless. I know all about the Canadians and their duplex loads because I live close to Canada and we see a lot of their shooters at our matches. In fact we use Canadian rules about duplexing in our long range matches to accomodate them. Some of their rifles crack like a smokeless load and they shoot real well but almost all the top winners are usually shooting straight black powder. I also know that when I used duplex smokeless and black loads the bore stayed cleaner and I did not have to use a blow tube but the rifle took me longer to clean than when I use straight black powder.

[The Double D]

Try a different brand powder, they aren't all the same you know.

Same granualtion in different brands all have different burn rates in different cases with different capacities.

Experiment.

One size does not fit all in black powder anymore than it does in smokeless.