How Do You Safely Duplex Load With Slow For Cartridge Powders?

[yodogsandman]

How do you safely duplex load with slow For cartridge powders? What's the strategy for working up those loads? I'd like to use the cheaper priced surplus powders but, need to know how to ignite it safely for a clean burn and to lengthen the pressure curve in the barrel.

 

[freebullet]

I don't practice duplex loads much. The only way to learn it is speak with those who know. It's not something that was allowed when this site started but....

As a rule of thumb make certain the charges can't move around & be intermixed. I won't go into load specifics in open forum. There are a few old timers around that can help. Just make sure what your doing makes sense to you.

 

[freebullet]

I'll add that it's even more work to find good loads that way. More time, testing, & risk.

 

[yodogsandman]

Thanks, that's exactly why I didn't mention which cartridges I wanted to load for. I'm not looking to be just handed a load that's worked for others without knowing the reasoning behind it, the why and what fors.

So, basically loads must be compressed to prevent the ignition powder from migrating.

 

[Rick]

I don't think it's that it wasn't allowed here, myself and a couple of others spoke up that it's something I know nothing about and an excellent way to get in big trouble in a hurry. I am hardly a ballistician and I have no ballistics lab to let me know the interaction between various powders. In other words the effect one powder can have on another's burn rate or pressure curve. I know just enough about blending powders to keep me from going there. In addition there are so many powders available today in a huge spread of burn rates it's simply not worth the risk to my fingers, eyes, firearm or spectators.

If anyone posts such info on this forum the forum has no claim, responsibility or liability as to what could happen. It's nothing more than what one person deems as valid. Take that info for exactly what you paid for it.
.

 

[Josh]

Blending and Duplexing are completely different processes. Unfortunately because of liabilities not many will openly share the information necessary to keep you from doing something wrong. I have duplexed a few loads for the slow military powders and would be willing to help you out in a PM. But only if you don't get your information from someone else, duplexing without help is way more dangerous than with some basic guidance.

PM me if you don't get the answers you want.

 

[KHornet]

My best advice is "if you don't play with fire, you won't get burned"! Period!

 

[Ian]

Hooboy. Ok, first, one has to consider the wisdom of putting themselves in a position where using a booster for a really slow powder is necessary in the first place. My advice is don't deliberately buy a bunch of slow powder just for the purpose of duplexing it unless you're trying to do something really special like shoot cast bullets accurately WAY past the normal accepted velocity constraints of bare lead....and already know what to buy and how to use it.

If you find yourself just wanting to experiment, work with buffers first, it will teach you a lot, particularly about how to respect more dangerous than normal things in handloading.

On to the philosophy. So you have some WCC872, 867, or similar. You've used in in your favorite cast bullet slinger (say, .30-'06) with cast bullets and just can't make it burn well. You've worked with a particular lot of it enough to know how much you can use with your particular combination of components. If you can fill the case with it and not encounter dangerous pressures or weird ignition, yet it still won't burn cleanly or give consistent velocities, then it's time to consider a "kicker" or "booster" charge to enhance ignition. Think of a booster charge as merely adding more spark to and extending the primer's heat. The way to use it is add about two or three grains of booster on top of the primer and subtract the same volume from a 100% load of the slow-for-cartridge powder. This all assumes that the grains of the booster and main charge are compatible shapes and sizes so they won't intermix much. Go shooting. Make observations and compare them to those of the 100% un-boostered load. If it seems prudent, add another grain of booster and repeat. The max I would ever go with a booster charge is about 10%, though some go 15% or so with certain booster/powder combinations. The idea is to make a powder like Reloder 50 burn more like Varget or 4831, and use your booster/main charge combo in different cartridges that would enjoy a powder in the medium-slow burn rate.

Sooooo, what to use for booster with smoldery double or triple-based cannon powder? A fast-burning, single-base, extruded rifle propellant. I'll leave it at that.

 

[9.3X62AL]

I have duplex-loaded in the past with one caliber, back in the days when WC-860 went for $3/lb. At that price, it made sense to at least try it out and see in that caliber if reasonable and accurate loadings could result. I got excellent accuracy and had no ill effects from the practice, and I likely fired more than 1,000 rounds of these loadings through the involved rifles. The caveats--1) the rifles were UBER-STRONG, OVER-BUILT examples in the caliber 2) my goal was accuracy and docile black-powder-level performances.

The only negative outcome I got was what I felt were premature burn-throughs of the cartridge brass at roughly the point where the two powders met inside the case after 5-6 firings in about 5% of the brass of 2 makes (R-P and W-W). If you have reloaded paper shotshells, these burn-throughs reminded me a lot of the burn-throughs seen on fired paper shotshells at the brass/paper junction after a number of refills and firings. Like the paper shells, I scrapped the brass showing these indicia. I did not get and have not gotten this burn-through at any time using homogenous powder loadings in this caliber, which I have loaded from docile to ferocious for close to 35 years.

I have discontinued the practice entirely, and will use the remaining WC-860 in a couple venues where it is far more appropriate. 100%-density loadings in 6.5 x 55 Swede jacketed 140 grain loadings give about 2475 FPS in my Ruger 77R so chambered, and that is right at 1896-level ballistics. The powder burns very cleanly. It does the same trick in 30-06 with 200-220 grain bullets, jacketed and cast, giving about 2100-2200 FPS with good combustion and good-to-stellar accuracy. A very BOOMY and satisfying report accompanies this work, docile pressures result, and performance is about 10% under factory standard velocities for this bullet weight-class. That's my story, and I'm sticking to it. Think of it in the light of a "nolo contendere"/"no-contest" plea in criminal court......."I didn't do it, and I won't do it again".

 

[yodogsandman]

So, subtract an equal volume of the "kicker" powder from the 100% filled charge of the slow powder.

Use no more than 10 % volume of "kicker" or "booster" powder for the charge.

Use a fast-burning, single-base, extruded rifle propellant for the "kicker" or "booster" charge. Don't know the reasoning for this.

 

[Ben]

UUUmmm, I wonder what beginning reloaders are going to think about all this ? ?

In the post above, I see the words ........risk, liabilities, dangerous.

Maybe this is why you will not be reading in a respected reloading manual about this type of thing ?

Ben

 

[Rick]

Exactly Ben, if such were excepted loading practice you would see it in every manual you ever picked up. I have never seen any mention of it in any loading manual. I admit it is just a guess on my part but I would be willing to bet there is a very good reason for that.

 

[yodogsandman]

This duplexing stuff is normally only done by experienced lab ballisticians for very large companies that make ammo to sell to the public. Powder is bought very cheap by the boxcar loads and tested in their labs for suitability and safety. They don't want reloaders to figure it out!

There are some duplex loads alluded to being published in load books many years ago over in the CBA forum. That thread was closed by the mods recently.

My wish is that no duplex load data is posted here. Only the theory and reasoning behind the use of duplexing loads. PM's would be the best media to share any actual loads that someone has tried themselves.

 

[yodogsandman]

If the site doesn't have a boilerplate disclaimer, it would be a good idea.

 

[Rick]

I doubt it's that they don't want reloaders to figure it out, if that were the case they wouldn't sell powder, primers, brass and reloading manuals in the first place. The reason they don't publish load data for factory loaded ammo is because there isn't any. They use powders that are on hand to come up with the needed results for a given cartridge. They have the labs and ballisticians and test facilities to do so.

 

[yodogsandman]

I missed a valid point..

"Kicker" or "booster" charges should not be allowed to mix, there should be two distinct layers held in place by the compressed load.

 

[Josh]

Mixing of the powders is a bad thing, you are correct, think of the powder as a layer cake not a marble cake. When I work up a duplex load the goal is just enough kicker to get a clean burn with no mummies. Once I reach that level, be it 3% or 10% I stop, once you get past clean burn then you are dealing with pressures that you have no way to measure.

 

[yodogsandman]

Found an excerpt some where??? Only relates to black powder duplexing.

EDIT: From Cast Boolits, Why does duplexing work? 8/23/2008

 

[Rick]

Black powder loads, so your saying it's fine to substitute smokeless in place of black?

I think it would be wise if members of this forum would like to share any type of duplex loads with another member they do so in private conversation. This is not a good direction for the forum to take in my opinion.

 

[Ben]

This is not a good direction for the forum to take in my opinion.

Ditto