Duplexing slow powders

[waksupi]

I have a few pounds of the square flake Turk powder. I'm thinking of using around 42 gr., for a velocity of around 2450 fps in my .375 H&H. That load leaves quite a bit of space in the case. I'm thinking WC 860 or WC 872 as filler. Anyone see any downside?

[flounderman]

They are loading 45-70 with 860 andabout5 grains of red dot. 860 would be more than a filler, with a kicker.

[runfiverun]

I think I would rather fill from the top rather than the bottom.
your grain amount and muzzle speed isn't too out of kilter suggesting the powder isn't slow enough to need a kicker charge.
I'd drop a grain and a half and try a grain and a half of filler in it's place.

[Texas by God]

Try it without the filler and stuff a ball of Dacron in on top of the powder. I did this in reduced loads in a .358 Norma with good results.

[OS OK]

Today was the first day I tried a filler of dacron...I fluffed it up real good and held it to .5 grains of weight and let the base of the cast push the last of it down from the top of the case mouth.

[Hamish]

Ric,

Just how many grains of WC872 would it take?

[Wayne Smith]

Ric, what velocity do you want? In my Steyr 95 8mm I used a couple grains of 3031 and a case full of 872 (I think) with the Frankenstein boolet and got 2300fps. I think you will boost your velocity considerably if you have enought space to need a filler.

[Nobade]

I have a few pounds of the square flake Turk powder. I'm thinking of using around 42 gr., for a velocity of around 2450 fps in my .375 H&H. That load leaves quite a bit of space in the case. I'm thinking WC 860 or WC 872 as filler. Anyone see any downside?

I started a thread in paper patched smokeless about using "reactive filler" and it was pretty much what you are describing. That is quite a bit of 860 to count as such, and you are going to build plenty of pressure to get it to burn right. Your velocity is going to be a lot more than what you are getting now, probably close to factory ballistics. But I wouldn't worry about pressure, the rifle won't be bothered by it. My main deal was to use 860 instead of cream 'o' wheat in small amounts to prevent the COW caking inside the shoulder. What you are proposing will be quite a bit more dramatic.If you're using jacketed bullets no sweat, if cast it might speed them up a bit much.

-Nobade

[waksupi]

The load should leave space for around 35-40 gr. WC860, WC872. My goal was to be able to reach factory equivalent velocity to use for the Safari Rifle Challenge world championship in July. I do have plenty other powders to use, and jacket bullets if it comes to that. Full power loads are required. I didn't think I would run into pressure problems, but figured someone had already tried something like this. I really don't want to use an inert filler.

[bearcove]

It sounds reasonable but now that powder is available again I'd just load off the load manuals data.

[ammohead]

I have been thinking along the same lines. Years ago I used a small amount of 3031 over the primer in a 338-06 load with wc860 as the original charge. This was just to clean up the unburned kernels and it worked. But it got me to thinking that maybe the slower surplus powders would work as a filler as well. I wasn't sure how to go about it though. It seems that if I had a powder and load that worked well with hefty velocity to begin with that I might want to back off a bit before I topped off the case with another propellant. Maybe start with about 70 percent of that load and move up with the original and down with the filler. This has been on my mind for quite a while, and now that all my loading equipment is at the Ely house and I am still in Fallon for a while yet, experimentation has taken a back seat to just loading and shooting.

One would think that if the original load was strong enough to move the boolit then it should probably move the fill powder with it before it started raising the pressures too much. But it also makes sense that at least some of that slow powder is going to burn adding to the mix. Maybe by having the load powder raising pressures faster than it can do on its own, its own burn rate may exccelerate, and it may kick in quite a bit of extra oomph. Where to start?

If you were going to assume that the fill powder is going to add to the burn then it would make sense to lower the initial bump of the load powder. And the presence of the fill powder would make lowering the load powder safer in terms of SEE sometimes seen by reducing loads with some powders. I would guess that somewhere as you approach the original loading there will be a spot where the filler would do its duty quite nicely. One difficulty is the recording of powder weights. The first component is easy just weight it before pouring. The filler is a little more problematic. You could just fill the case to 100% but how much is that? If you found something that really works you will want to accurately repeat it. I guess you could put the load powder in already weighed then top off with the fill powder, dump it all out and weigh it and do the math but I wouldn't put it back in the case after mixing it up. Could be a fun project. I am going to follow this one.

[Nobade]

Just use all filler powder to set your measure, then switch to the real powder.

Sent from my Moto G (4) using Tapatalk

[waksupi]

Just use all filler powder to set your measure, then switch to the real powder.

Sent from my Moto G (4) using Tapatalk

That's kind of where I started, but the Turk bulks differently than the other powders. Get's you close in the ball park.

[William Yanda]

I started a thread in paper patched smokeless about using "reactive filler" and it was pretty much what you are describing. That is quite a bit of 860 to count as such, and you are going to build plenty of pressure to get it to burn right. Your velocity is going to be a lot more than what you are getting now, probably close to factory ballistics. But I wouldn't worry about pressure, the rifle won't be bothered by it. My main deal was to use 860 instead of cream 'o' wheat in small amounts to prevent the COW caking inside the shoulder. What you are proposing will be quite a bit more dramatic.If you're using jacketed bullets no sweat, if cast it might speed them up a bit much.

-Nobade

Nobade, you mentioned the COW caking. Did you toast it before you used it as filler? I have some grits which I toasted over a year ago and they are still very loose in the original cardboard container.
Bill

[richmanpoorman]

Duplex smokeless loads can be found in NO responsible loading manual. The claimed benefits escape me 100%.

If you are finding whole grains of unburned powder in your bore, you are using the wrong powder/bullet/primer combination.

Powder is cheap, using unknown surplus powder is akin to running bald tires in the Alps ....... dumb-de-dumb-dum (apologies to South Park)

[bearcove]

No it can't cause they have liability you can't imagine.

But it is nothing new. Its not something to freak out about, if it is past your experience read and maybe learn something.

[ammohead]

richmanpoorman,

With only 107 posts you are to be forgiven for slandering the quest for unknown knowledge. As far as "unknown surplus powders" there are few that are unknown on this board and many have listed loading data on the "castpics" site. We as a group have been gathering and diseminating such data for the last 18 years or so all the way back to the original "Shooters" board. If all we did was gather here to discuss what was already known there would hardly be reason to gather at all. There's facebook for that and I'm not interested in a picture of someones dinner. This is a site for learning and sharing and one of the very best. Maybe the single largest source of information on cast boolits in existance. It surely harbors some of the very best minds on the subject one of them being the originator of this thread. If you can't contribute to the conversation and can only belittle someones efforts maybe you should just lurk. No one likes a naysayer.

[rbuck351]

ammohead
Do not add a slow filler powder to an already working load. Start with a powder you know you can fill the case with without to much pressure. A case full of 5010 will shoot safely in just about anything. 870 I'm not so sure and would probably start with about a 90% case full and work up to a full case and then start replacing a few grains of 870 with something like 4198 over the primer. Then increase the amount of faster powder a grain or 2 at a time and reduce the 870 in equal volumes until burn cleans up. Once burn cleans up you will probably be near 2000 fps but chrono to be sure and work up from there. This can be safe if you go at it properly. If you already have a load that is creating enough pressure, the added fill powder will burn quite well and add a lot more pressure.

[waksupi]

Duplex smokeless loads can be found in NO responsible loading manual. The claimed benefits escape me 100%.

If you are finding whole grains of unburned powder in your bore, you are using the wrong powder/bullet/primer combination.

Powder is cheap, using unknown surplus powder is akin to running bald tires in the Alps ....... dumb-de-dumb-dum (apologies to South Park)

Considering that several manuals have been written from info on this forum, and this has been the recommended information resource in the past by Lyman, you may want to re-think that. Duplexing goes back over a hundred years, and there is plenty of info about it if you look. This is the advanced handloading course. If you don't feel comfortable or competent, by all means, do not experiment with this.

[runfiverun]

I wouldn't want to use 35-40grs of a filler powder.
your initial charge would light some of it off for sure especially on top of a 42gr charge giving the velocity your getting now.
the pressure alone would insure your gonna burn some of the added powder.

i would attack this from a different angle.
I think I would first try a case full of the 860 and work back by adding a kicker of something like 4198 to help it achieve pressure and watch my velocity's as I went.

if I were to use the other 2 as a filler powder it would be on top of something slow enough to give me at least an 80% case fill but with pressures in the 45K area.
that way if [when] the powder did ignite it would have the boolit moved down the barrel guaranteeing me room to handle the extra gas volume.
the slower powder should also protect the base of your boolit which would help accuracy at velocity.

I think I would also try a paper disc separator between the two powders and also try to retard the initial ignition to keep it all in the first powders column.

anyway just some ideas that might help.