Duplexing slow powders

[Larry Gibson]

That is pretty much how I have proceeded. 10 gr. of the Turk filled with WC860 is giving me around 2050 fps. According to theory, I would only need another 8.5 gr. to reach the velocity I need.

Waksupi

I have a small amount of WC860 and the Turk powder. I do not have that mould though. If you want to send some of your cast bullets I can pressure and velocity test that load and potentially work up? That way we can see what is really happening with such loads. PM me if interested.

Larry Gibson

[waksupi]

Waksupi

I have a small amount of WC860 and the Turk powder. I do not have that mould though. If you want to send some of your cast bullets I can pressure and velocity test that load and potentially work up? That way we can see what is really happening with such loads. PM me if interested.

Larry Gibson

Done!!!

[ammohead]

Now we are really getting somewhere. I can't wait to hear about these results. Thanks for stepping up to the plate Larry. I know I shouldn't be surprized. The pioneer spirit lives.

[Buckshot]

...............When I started duplexing in the mid/later 90's, one of the "Burrito Shooter's" would move his stuff 2-3 benches away if I admitted that I'd be shooting some duplexed stuff (that was all 45-70) . After a couple weeks (We shot every Tuesday) he 'd become very interested in what I was accomplishing. He'd had a Turkish M38/46 rebarreled to 35 Whelen and with a case full of WC 872/860 (I don't recall which now at this late remove) he was getting about 1800 fps using the heavy Lyman 358009.

It wasn't too long after that he also tried it using what I'd done which was 1, then 2, and so on up to 5.0grs of H4198 under a casefull of the slow ball and the 300 gr cast slug. In any event he ended up at 2000 fps and a clean burn with accuracy as good as before, and best of all a clean bore, and was able to utilize that stuff we were buying (at that time) at $3.50/lb in 8 lb jugs delivered!

...............Buckshot

[waksupi]

...............When I stated duplexing in the mid/later 90's, one of the "Burrito Shooter's" would move his stuff 2-3 benches away if I admitted that I'd be shooting some duplexed stuff (that was all 45-70) . After a couple weeks (We shot every Tuesday) he 'd become very interested in what I was accomplishing. He'd had a Turkish M38/46 rebarreled to 35 Whelen and with a case full of WC 872/860 (I don't recall which now at this late remove) he was getting about 1800 fps using the heavy Lyman 358009.

It wasn't too long after that he also tried it using what I'd done which was 1, then 2, and so on up to 5.0grs of H4198 under a casefull of the slow ball and the 300 gr cast slug. In any event he ended up at 2000 fps and a clean burn with accuracy as good as before, and best of all a clean bore, and was able to utilize that stuff we were buying (at that time) at $3.50/lb in 8 lb jugs delivered!

...............Buckshot

I figured I wasn't the first one to tread this path. I have just never considered all the possibilities before.
I sent Larry some bullets, and I'm sure looking forward to seeing his results.
I'm not as old as you are Rick, I had to give $4 a pound for the WC860/872.

[oldblinddog]

I am curious as to whether there are two pressure waves with a duplex load.

[Larry Gibson]

I am curious as to whether there are two pressure waves with a duplex load.

We shall soon see.......

Larry Gibson

[wmitty]

Very interesting thread!

[Larry Gibson]

Have test loads loaded but have company coming in this week which will delay testing..........

Larry Gibson

[iplaywithnoshoes]

I am curious as to whether there are two pressure waves with a duplex load.

A safe duplex load should not create a compound pressure curve. The kicker should simply increase the rate of heat transfer and the duration of exposure to the main charge.
Ideally, one should use an "easy to ignite" powder with a medium-high burn rate like 3031, 5744, 4198 etc

[oldblinddog]

A safe duplex load should not create a compound pressure curve. The kicker should simply increase the rate of heat transfer and the duration of exposure to the main charge.
Ideally, one should use an "easy to ignite" powder with a medium-high burn rate like 3031, 5744, 4198 etc

My thought exactly. Still, I'm curious about what Larry's pressure trace looks like. If they look "normal" that will tell a lot. I would also expect that a compound waveform would most likely be an indication of where not to go.

[Elkins45]

I will be very interested to see what the testing reveals.

[jonp]

I'm following this with great interest. I just found 48lbs of W860 in the garage I bought from Jeff a few years ago and never had a chance to work up a duplex for. Nobade gave me a ton of help in this and I saved all of his pm's but I just didn't find time to do it.

I know, how can you forget 48lbs of powder?

[Larry Gibson]

Completed initial testing today.........compiling it and will post soon.....maybe tonight......

Larry Gibson

[Larry Gibson]

In considering whether to test a 375 H&H duplex load (I value my M70) I gave it some thought. I had not really considered duplexing before as I've not invested in the really slow burning powders so had no need to. Also I've so many test irons in the fire it wasn't on the top of my "to do" list. However, Waksupi's thread here and on goodsteelforums.com peaked my curiosity. In thinking it over I relied on my own experience with BP duplexing and previous post on the topic by Novade. I found a duplex BP load, if done correctly, to be quite safe, useful and accurate. I saw no reason why it couldn't be done with the powders Waksupi was wanting to use. My standard 375 H&H load uses 300 gr jacketed bullets (Hornady 300 SPBT, 300 RNSP and the 300 FMJ) over 78.5 gr of AA4350 in NS'd R-P cases sparked by WLR primers. They ran 2570 fps at 57 - 58,000 psi when I developed the load in Washington 7 or 8 years ago. Thus I concluded using 5 gr of the Turk powder with 75 gr of a slower powder than AA4350 (WCC860) on top of the Turk '43 powder under a 287 gr cast bullet should be "safe".

I had the 375 H&H already with a strain gauge on it for pressure measurement, I had pulled down Turk '43 powder and all I was missing was the bullets and some WCC860. Waksupi sent the bullets and Bjorn souveniered me some WCC860. I loaded one of Waksupi's PC'd NOE 378-279-FN bullets in a split necked case to check seating depth in the test Winchester M70. Turns out they fit quite nicely in the case neck.

Attachment 196270

Being able to see the bottom of the bullet in the case gave me the correct load density needed to prevent migration of the powders. Waksupi also said he used a small tuft of Dacron on top of the powder for the bullet to push down on as "insurance". I decided to do the same. I then loaded a round with 5 gr of the Turk '43 over the primer and then filled the case with WCC860 to the base of the bullet. I then weighed both charges and subtracted the 5 gr. That gave me a charge of 75 gr WCC860 to start with using 5 gr of Turk '43.

For the psi work up I had to figure how much to reduce the WCC860 as I increased the Turk '43 powder I then filled the same case to the same level with just WCC860 and weighed that. It came to 81.5 gr. So basically 6.5 gr WCC860 equaled 5 gr of the Turk '43 powder. I decided on increasing the Turk '43 powder 3 gr per test which meant a 2 - 4 gr reduction (I was cautious at first so went with 2-3 gr changes) of WCC860. I was hoping to work up to 2500 fps or where accuracy went erratic before pressure became an issue.

I did size Waksupi's bullets at .377 and lube them with Lar's 2500+ as my experience previously with other PC'd bullets indicates lubed PC'd bullets are more accurate and do not foul the barrel. To test Waksupi's initial load I loaded 8 rounds of 5 gr Turk '43 with 75 gr of WCC860 on top. Then a small tuft of Dacron was inserted and the bullet seated on top of that. I then loaded 14 rounds for the psi workup loading 8/72 (Turk/WCC860) through 47/27 (Turk/WCC860) gr in the increments listed on the Oehler test data sheets.

With all that done last Tuesday I loaded up all the Oehler M43 accouterments and was off to the range. It did not go well. I shot 2 rounds of Waksupi's load and knew the strain gauge had apparently cracked. So it was load everything back up and head home......

The last couple days I double checked everything on the M70. Sure enough the strain gauge had cracked. As it had been on for 7 -8 years and a lot of heavy recoiling rounds had been fired a couldn't really complain. Yesterday I put a new strain gauge on. It is a procedure because it is permanently affixed. The old gauge had to be completely removed down to bare metal, the barrel metal prepped, the new gauge prepped and then glued on, then the leade wires attached. After that I hooked it up to the M43 and computer and all checked out. All appeared well. However, only shooting can tell if it's really good to go.

Woke up at daylight this morning and the temperature was only 78 degrees and the wind seemed manageable so I loaded everything up and headed to the range. Set up went smoothly and the new gauge checked out. The rifle is a Winchester (New Haven) stainless M70 375 H&H. Scope is a Leupold 1.5x5X with duplex reticle.

Attachment 196274Attachment 196275

I then set up to shoot the remaining 6 rounds of Waksupi's load. Target was at 100 yards. 1st shot out of the clean barrel went high left. The pressure was 37,500 psi at 2078 fps. The pressure trace looked fine. I then shot the remaining 5 shots which went into a nice 1.9" group. Looking good with no problems so far.

Muzzle velocity averaged 2096 fps for the 6 shots with an average psi of 38,000. The SD and ES for velocity and psi were excellent. If you look at the rise of the pressure trace you can see where the pressure eased a bit as the Turk powder burned out and where the WCC picked up by itself.

Attachment 196276Attachment 196279

[Larry Gibson]

The PSI workup

I then ran the 14 shot psi workup test of increasing the Turk '43 powder while decreasing the WCC860 powder. The charges were from 8/72 (Turk/WCC860) through 47/27. All went well with relatively smooth pressure traces. Looking at the pressure rise of each increase/decrease of Turk/WCC860 we see the slight psi drop off decrease as the amount of Turk '43 is increased. Looking at the target you can see where each round hit. Six rounds, 8 through 13 hit into a very nice group right at point of aim. Rounds 11, 12 and 13 hit the magical 2500 fps. That is very equal to factory 300 gr 375 H&H performance. I will load 10 shot tests of loads 11 and 12 to test for a more complete pressure picture and for group. If either does well that would be an excellent load for anything walking this continent........

Attachment 196280Attachment 196281Attachment 196282

It would appear that duplexing with these components is safe. Is it safe with other components......I don't know and won't conjecture. However, since the Turk powder is very close to 3031 and H4895 I will load a test string substituting H4895 for the Turk '43 powder, probably load 11.

Be safe.

Larry Gibson

BTW; after completing the duplex test I let the barrel cool, cleaned it and shot a 10 shot test of my 300 gr RNSP jacketed load (brutal off the bench......). The muzzle velocity was 2607 fps at 57,500 psi......exactly where it should have been.........group was 1.75".........

[oldblinddog]

The trace does look fine. It is interesting that you can "see" the two powders in the trace.

[waksupi]

Larry, thank you so much for doing this testing. I felt it would be a safe practice, and you have confirmed it. I hope it helped not only me, but others sitting on a bunch of surplus powder. I suspect the same powders would work well in other chamberings, but should as always, be approached with caution. I'm only a bit over a month away from the shoot, and will do a bit of work getting the cat's meow load for my rifle. Extremely grateful to you!
I did receive a message from a person about benchrest accuracy for my purposes. For this shoot, that is not really a consideration. There is only one static shot where you shoot your tie breaker off hand, and pretty much all other targets are moving, many of them directly towards you, or swinging side to side.

[Larry Gibson]

You're welcome.

I have 3 loads of the Turk/WCC860 powder loaded for testing; pressure, velocity and group. 7 rounds of 26/50, 8 rounds of 32/42 and 8 rounds of 38/36. I also have reading for the same testing 10 each of 32 gr 3031/43 gr WCC860 and 32 gr H4895/43 gr WCC860. That has used all the bullets you sent and depleted my meager supply of WCC860. The initial load I already tested (5 gr Turk/75 gr WCC860 at 2096 fps) should be a good starting load for those just wanting a "plinking" load in their 375 H&H. I would suggest dropping the WCC860 amount to 70 - 72 gr and using a bit larger Dacron filler. I was using NS'd fire formed cases so the exact amount with FL sized cases might be a gr or two different.

With this last 5 tests I am looking for a 2 - 2 1/2 moa load that pushes 2350 - 2500 fps for a cast practice load close to jacketed 300 - 350 gr bullet recoil. Of course it would also be suitable hunting. My 375449 is only 10 gr less than your bullet so, if all works out, it will give me a good idea of loads to further test......just have to scrounge up some WCC360 is all..........

Larry Gibson

[swheeler]

Finding that WC 360 will be tough!