Duplex and Triplex loads

[Tommie]

A couple months ago I had a long conversation with one of the "old timers" of competitive benchrest. Among many other eye-opening revelations, he told me that most,if not all) top tier benchrest competitors are use duplex or triplex loads. While I mentioned that NBRSA and IBS match results always list the winning loads and I've never seen such a thing shown, the man said "Do you think those guys are really going to reveal their winning recipe?" He went on to explain the advantages of loads containing two or more powders.

Honestly, the concept frightens the heck out of me. I don't intend to try the theory but I am curious. Are these powder recipes handed down from person to person? I've read a few articles which briefly mention it. Besides for 454 Casull loads in PO Ackley Handbook #1, I've seen basically zero information about the subject in print.

Tom

 

[CatShooter]

You never hear of it because it's a taboo subject - kinda like having sex with your gorgeous cousin.

I have shot Duplex loads, but not triplex.

When you bring up the subject, the screaming can be heard across town, so I won't say anymore about it!


.

 

[CoyoteVision]

I must say, I can't believe that has much to do with being a top benchrest shooter, but I've never tried it and won't be trying it.

 

[billmo]

CoyoteVision, That is how the competition wants everybody to think. The longer the opponent thinks that way, the longer the winners are in a category to themselves. But I agree, I don't think I want to start mixing powders unless I was educated a heck of a lot more concerning burn rates and pressures involved.
On the other hand, I'm no BR shooter. Bill

 

[Preacher]

I know a few folks that mix up different lot numbers of the same powder but mixing the different powders together is just to scary to think about....

 

[Louisiana Shooter]

If I understand correctly, the powders are not mixed together but layered.....a fast burning powder is loaded against the primer,to help with ignition of a slower powder) then the main charge is loaded. The charges completely fill the case or a filler is used so the powder charges do not shift when the cartridges are handled......at least these are my understandings of the things I have read about the subject, I have no experiencial knowledge at all..........just what I've read about it.


I've never read anything about triplex loads.

 

[Cheechako]

Tom

I have been shooting both point blank and long range Benchrest for a lot of years and don't know anyone who is now, or ever has shot duplex or triplex loads.

I and others do blend powders on occasion either to use up small amounts of different lots of the same powder or to create our own number but we know exactly what we are doing.

And, except for a very few paranoid shooters, there are no secrets. Most guys I know will tell you exactly what they use and then dare you to beat them with it.

Either that "old timer" was pulling your leg or he simply doesn't know what the hell he is talking about.

JMHO

Ray

 

[Eddie Harren]

I'm talking short range BR here. A few years ago some of the shooters, that I know, were unhappy with the burn rate of N133. They tried to re-conform it to the "speed" of the previous lot. They did this by mixing lots of N130 with N133. I don't know how well it worked. Some shooters were mixing Moly powder with their H322. I was told that it lowered the Temp. without lowering the velocity. One thing remains true. Short range BR shooters seem to be willing to try just about anything, in their quest for a "Zero Group", and sometimes it works.

 

[CatShooter]

"... I was told that it lowered the Temp. without lowering the velocity."

That can't happen - if you lower the temperature, then you lower the gas volume AND burn rate...

... and lower the velocity.


.

 

[expiper]

Lynn....good morning...the only thing Im a blendin at the moment is the new snow with the yellow snow!!!....it is big job...but somebody has to do it..and OBTW ..did I ever tell u about my "ugly" cousin that went nuts when Elvis died??? It is a good un for arund the campfire...
I have a lil blend that I will be tryin in sunny cal. in my ole' worn out bbl..,billy)if I can make the trip...I look foreward to seeing you guys....say hi to Dad...Roger

 

[Tommie]

Ray,

I won't question the knowledge of man who told me about this practice in benchrest. To avoid getting him a pile of hate mail, I won't divulge his name. However I am comfortable in stating that 90% of the people on this board have heard of this guy and know his accomplishments. I guess it's possible the guy was pulling my leg - although I don't know what he would have to gain by doing so.

For the sake of discussion, let's assume that no benchresters use duplex of triplex loads. I'm much more interested in how the loading technique is put into practice. Specifically, how does a person come up with a recipe of X grains of powder A with X grains of powder B without blowing the gun into the stratosphere.

Tom

 

[Rustystud]

Mixing powders outside a laboratory gives a whole new meaning the "big bang theory".

I know of folks having shot duplex loads with compressed loads or using fillers to cause compressed loads.

This is not recomemded idea and should be refrained from in practice.

Rustystud

 

[Rust]

Layered loads were once common is large bore pistols when more suitable powders were not available, but that didn't make them a good idea for just anyone to play with. There have even been layered loads for large bore pistol available commercially for a little bit. Don't know if there still are.

Layered loads were once used years back trying to get unsuitably slow milsurp powders to work in large magnum chamberings. Very mixed results.

Layered loads have been used and are still being used in .50 BMG and in my mind this might be the only place where it might make just a little sense.

Blended powder loads. Yeah, it's done, it's probably still being done. The most blending I've ever done is to mix the last 1/2 lb or less of one lot of RL-15 into the new batch of RL-15 and that's about as far as I'll go. Differing powders from the same manufacturer I wouldn't mess with, different powders from different manufacturers, well, even less.

Powder is blended for military applications, by the trainload sometimes in the past, done by folks with large ballistic labs and equipment no one else has.

But there is no "magic load" that is stable in any condition, produces single digit ES/SD, good for 100 to 1,000 and produces bugholes. There are good loads that some folks learn to shoot in a well built rifle under varying conditions. Want to shoot good groups? Learn how to read the wind.

 

[Cheechako]

There still seems to be a lingering confusion regarding duplex/triplex loads and powder mixing/blending. They are NOT the same thing. Not even close.

Doc Ed - I have used VV N 131.5 in my long range BR pistol and I know several shooters who used it for a while in their rifles. In the end, though, it didn't shoot any better than 130 or 133 by itself so maybe VV knows what they're doing after all.

Tom - As to how to come up with a recipe for duplex/triplex loads, I don't think you'll find it anywhere. Outside of the more common practices such as black powder shooters use to get cleaner burning, you'd need a ballistic lab, and a lot of head-scratching and guessing. Do a little reading of some of the past experimenters such as Ackley, Keith, Sharpe, and you might find a little information. But I think you'll find that they did it the old fashioned way - a little of this, a whole lot of that, tie it down to that old stump, now let's get behind that big tree and light this thing and see what happens!

Duplex/triplex loading is one of those subjects that comes up every couple of years when someone thinks they have discovered the golden fleece only to find later that it has been tried countless times before with the same disappointing results.

That and frontal ignition.

Ray

 

[dmickey]

With about 40 years of reloading experience,) it's my opinion that with a duplex load you are asking for trouble. With a triplex load you are begging for it!!

 

[Cheechako]

Dennis

Well said.

Ray

 

[Tommie]

I totally agree that it's an "iffy",at best) practice and have no intention of ever trying it. I'm curious, but not THAT curious!

 

[tightneck]

Actually, mixing powders of the same, or VERY close in burn rate is probably no more dangerous than loading a single powder. Why would it be? Heck the factories do it every day in factory ammo.

I'll give an example. Yesterday at the range I cronographed 3 different powders in the 30BR. H4198, RE7 and N130. All three powders loaded to the same weight gave velocity readings within 50 fps of each other at the 3000fps level. Now on the other hand, mixing 4350 and 4198 to speed up the 4350 in your .308 would be a big NO-NO.

 

[BHarvey]

I have used various duplex loads in the past, and if done carefully, MV's can be greatly enhanced.

I used different ratio's of 2 powders and kept the overall charge weight the same.

Works great, was safe, and accuracy was also very good.

 

[Cheechako]

. . . MV's can be greatly enhanced. . .

B

I'd be interested in learning the details.

Could a simple switch to a more appropriate powder produce the same results??

Ray