'Duplex Loads'

[ranger335v]

"I understand 'Lyman' at one time, made Bench Mount Powder Measure-dispensers, having two simultaneous acting resevoirs and adjustable measurering-dispensers, for use in Cartridge re-Loading, which dispensed Black Powder and Smokeless at the same time, for a combined Load.... using a small amount of Smokeless under a Black Powder Charge, was quite popular to do."

Whomever gave you that information is wrong. First, there were no such dual chamber powder measures made by Lyman nor anyone else and mixing powders is quite hazardous. And, while it's true that duplex/triplex loading was tried for awhile it was never poplular. A very few of us tried it, none kept it up and it faded from sight long ago, and properly so.

Today's powders offer such a wide range of burn rates that trying such things is pointless.

 

[Oyeboten]

Hi Ranger5v,



The 'Lyman' Powder Meterer-Dispenser in question is something I saw a photograph of.


Anyway...


Thanks for your concern

 

[evan price]

Some folks tried duplex smokeless loads to try and get more velocity without higher peak pressure. The theory was the slower powder would start the bullet, and about the time the pressure curve was dropping (the bullet was traveling too fast for the powder to accelerate it any more) the fast powder at the top of the powder column would give it another kick.

The theory behind duplex loads is that you use a large, bulky, slow, hard to ignite powder for the bulk of the load. To get it to reliably ignite you need a small charge of fast powder on the primer to get a good flame going, a "booster" that takes the small primer flash and gets it hot quickly so that the bulky, slow powder starts burning well.
For example, loading a 30-06 rifle case, you drop 5 grains of a fast shotgun powder like 700-X in the case. Then fill it up with a very slow rifle powder like 50 bmg. Then place your bullet and make a compressed load. IN theory this lets you have the most benefit of the slow powder in a smaller case size while getting consistent and full ignition.

 

[Oyeboten]

Hi evan price,


Thank you...



You know...I'm pretty sure I had read of BP being used as primary small charge, for igniting a harder-to-ignite Smokeless upper-charge...as well as anecdotes of the opposite arrangement-order.


Though my own anticipation, was for using a tiny bit of Smokeless, under the BP...for other reasons.


This possibly underlay my earlier mis-speak, regarding which is 'under' which...



Anyway...I enjoyed the .30-'06 mention...very nice..!

 

[Venado]

I use to do duplex loads with the hotter powder right above the primer, but found that a triplex load, using fast, slow, and fast is much better. As mentioned above, use a slower powder than caliber usually calls for, and have a compressed load. I challenge anyone to duplicate the results with a single powder.

 

[griz]

I stand corrected, I guess I heard/understood wrong. Just out of curiosity, what slow powder did they use that required a booster charge just to get it lit?

 

[Offfhand]

Thanks for all the knowledgable comments about duplex loads, you guys have a great sense of humor. I'll be laughing all day.

 

[evan price]

I stand corrected, I guess I heard/understood wrong. Just out of curiosity, what slow powder did they use that required a booster charge just to get it lit?

There are many slow powders derived from military surplus rounds that have been demilled, such as .50 BMG and 20mm cannon rounds. These burn very slowly and may not get a full burn in the relatively shorter barrels of most rifle.

 

[Oyeboten]

Anyway...image ( e-bay Listing ) of an old "IDEAL" Duplex Powder Dispenser for Bench Loading/Re-Loading -

http://cgi.ebay.com/Ideal-No-6-Dupl...emQQptZLH_DefaultDomain_0?hash=item335904e05a


No affiliation with seller...just thought you all may enjoy seeing it.


And...for those who refused to believe such a thing ever existed, also.

 

[Oyeboten]

More Treasures here -


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


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

 

[EddieNFL]

I recall reading about a few guys experimenting with duplex loads in the early IPSC days trying to make major in .38 Super and, IIRC 9MM.

I read quite a bit about front ignition, but never was motivated enough to try.

 

[ranger335v]

Seems every couple of years the "new idea" of 'blending powders' or duplex/triplex and front ignition for some magic results resurfaces in our midst. Thankfully, it seems to sink again with no more talk of such things for awhile. Its strongest pursuers in the past never accomplished much, if anything, and with the wide assortment of powders we have today it would do even less than previously.