Duplex loads: Stack or mix?

[olegburn]

In one of the recent threads folks say: Post more often!
Well,I will comply...

To those with good knowledge of Duplex loads:
Is there difference in ballistics,ignition,etc in loads where one STACKS powders(I imagine booster first,then main load and sabot/bullet on top)
or MIXES them?
For hunting I wish I could just mix 'em,so I can carry them in my speedloaders.
olegburn
P.S: Has anyone here have done pressure testing with Duplexes for safety and such?

[pposey]

I seem to remember that it nixes the benifits of the duplex,,

[edge]

Actually stacked seems to work the best, but I have done both.
It takes more time than you might imagine to make a truly homogeneous mix.

I have not tried to NOT mix and putting both in the same container. If I did that I would do it in reverse order so that the fast powder were last in the container.

When RB first started this board on duplex he and some others experimented with what was called reverse duplex with the slow powder in first and the fast powder second. Mainly it was done to show that it was save to do in case someone messed up, but some used those loads intentionally!

Often the fast powder may be small in size and worry about it migrating through the vent liner could be a hazard. With the larger grained powder on top this would be alleviated.

edge.

[olegburn]

4759 and AA5744 that I see mentioned as a booster a lot are large extruded powder-not likely to go thru VL,don't you think,edge?
Just my observation.
Now,was there actually velocity difference with stacked vs mixed?
Once primer goes off,I imagine,things start happening pretty fast and would powder location make difference how overall load burning develops?
Edge,how you define "best" for stacked duplex?
Did you chrono both loads?
Thanks!
olegburn

[edge]

It has been a long time since I personally tested this. The POI was slightly different so I would assume that the velocity was different too.

I would bet that if I spent time tuning the load for a mixed load that it would be just as accurate as a layered load.

4759 and 5744 are both good boosters and not much risk of falling through the vent liner.

I would suggest that you start down 10% and work up a mixed load if that is the way you would prefer to shoot it. Then try stacked to see if you find a difference.

edge.

Here is a target with regular duplex and then mixed duplex.
I am not a target shooter so there may actually have been very little difference ;D ;D

[dougedwards]

I actually pour both powders into the same vial then cap them off with a styrofoam packing peanut. This method has proven effective for me as I can easily pour the booster powder in first with very little mixing occuring.

Doug

[grouse]

I'm surprised SW has not posted here yet. He reminded me the other day how much he does not like the terminoligy mixing powders. ;D

[edge]

Here was another test that I had done where the results were definitely not as good.

edge.

dougva.proboards.com/index.cgi?action=display&board=Savage&thread=9617&page=1

[orion]

Just some food for thought for you duplexers, check out the wad that Remington has come out with for its hypersteel steel shotgun loads. It appears to have an inner column or space for a fast powder with an outer column or space for a slower powder. I imagine a sabot could be fashioned in a similar manner. Apparently it holds the two powders appart to prevent mixing. For all I know they may have stolen the idea from the guys on this board.

[edge]

Interesting:

www.thefirearmblog.com/blog/2010/05/17/how-remingtons-rocket-shell-works/

[Dave W]

Stacked vs mixed(circled in red ink) at 200yds.

[olegburn]

So,the verdict is: mixed is no good?

Bummer.
I was hoping I could reload faster with mixed loads.
Or maybe,I will wait 'till Edge done tuning the mixed load ;D
To be honest,I haven't shot duplex mixed or stocked yet.
Was hunting since I posted question.
BTW-may we never forget the benefit of not needing to clean your ML after each hunt,that Savage gives us-I got home 10:30PM last night,showered,brushed my teeth,not gun and went to bed!
End of story.

DaveW,was this just a single group or you had it repeated?

[dannoboone]

"P.S: Has anyone here have done pressure testing with Duplexes for safety and such?"

RB did a lot of pressure testing at the time he introduced duplex loads. He
found several loads which produced faster speeds at less peak pressure than
book loads.

I once toyed with the idea of loading with an accurate duplex, then using an
accurate single powder load for backup loads. However, I found that by
gluing a small charge powder vial on top of the larger main powder vial, a
field reload didn't take much longer at all.

[Dave W]

Oct 21, 2010 7:42:36 GMT -5 olegburn said:

So,the verdict is: mixed is no good?

Bummer.
I was hoping I could reload faster with mixed loads.
Or maybe,I will wait 'till Edge done tuning the mixed load ;D
To be honest,I haven't shot duplex mixed or stocked yet.
Was hunting since I posted question.
BTW-may we never forget the benefit of not needing to clean your ML after each hunt,that Savage gives us-I got home 10:30PM last night,showered,brushed my teeth,not gun and went to bed!
End of story.

DaveW,was this just a single group or you had it repeated?

The stacked method was repeatable, never tried mixing again other than a 100yd group which was not too bad. The extra 100yds really opened it up as you can see.

[zakjak221]

oleg,

Good question, and one that I've wondered about as well.
I've not used duplex either and haven't got around to askin.
So now we know.
Didn't know about the Xelerator shells either.

Mark

[youp50]

RB has many duplex pressure curves on the old board. To my way of thinking he made good sense.

He also concluded that there were two good reasons for duplexing. One being optimum pressure for greater velocity while maintaining safe pressures. And cold weather ignition dependability.

Richard will attest to the fact that blending the booster/main load will cost approximately 150 fps versus layering.

Edge and Dave have both posted a target showing different results from blending powders.

Research the old board for pressure traces from RB. After you have decided you want to duplex stay within recommendations and do your range work. Duplexing is fairly simple, just be sure you are of a sound mind and have developed a safe, solid method.

[Dave W]

Hornady is mixing in a cartridge with accuracy so I see no reason a mix could not work for our application as Edge said, just take some experimenting to find the right ratios, certainly not the current ratios that most use. A possible winter time diversion.

[Harley]

Let's not lose sight of the fact that layered duplexing has been proved - proved safe, proved close-grouping, proved repeatable, proved to be cold weather reliable. Let's also not nitpick more than we have to on the "problem" of loading two separate powder vials. In real life, adding the second vial increases my reloading time 10-15 seconds.

Harley

P.S.: DaveW's comparison (Reply #10, above), while only one group, is good enough for me.

[edge]

Oct 22, 2010 6:16:54 GMT -5 Harley said:

SNIP.

P.S.: DaveW's comparison (Reply #10, above), while only one group, is good enough for me.

Hmmm.......

IMO, that is not enough for me!

I bet that many folks read that someone used a load that produced great results, then they tried it and it was not super for them at all.

If they stopped there then they may miss out on a good powder but it may need tweaking in their rifle using their particular routine.

Some folks use wonder wads and some use fiber cards and I bet they both shoot a bit differently in different rifles.
Now that group by Dave W with 16/59 stacked may do better at 15/60 or 17/58 mixed but you won't know until you try...IMO.

I certainly would not throw away completely a load that shoots 4 inches @200 yards on the first try, especially since it actually grouped to the exact POI horizontally as his stacked load!

I am not a great bench shooter and rarely adjust my scope except at the beginning of hunting season if my load has changed. When I work up loads I always look for loads that hit close to my horizontal POA. I will tweak any load that hits close horizontally. The vertical component is generally velocity.

edge.

[DHinMN]

As for handling duplex loads in the hunting field, get some speed loaders that have the powder on one end and a place for a bullet on the other. Instead of the bullet put in the starter powder. Simple enough, you shouldn't get mixed up in the loading, and just about as fast. Just don't put the wrong end in first. You wouldn't need many.

[olegburn]

Main reason I'm looking into the Duplexing is that I found that H4198 work real well for me in .50-
I moved to shooting 200-300 yrd and at first I was getting 6" or so at 300,but with few more sessions I bettered it to less than 3" on couple occasions. Bullet drop is right where I want it for my Nikon BDC reticle. My problem is in Ohio when it gets cold around ML season I had misfires and hangfires.
So following advice from this board I look into duplexing for relaibility.
Now,like Harley says it is easy gluing two containers together and be done with it-I agree,for except that I recently started downsizing my hunting outfit.
I'm wanting to get rid of backpack or fannypack which I pretty much did. I carry everything in my vest and on the gun( I attached small pouch for speedloaders).
Given that I really like to stick to speedloaders if I can.
Extra 10-15 seconds sometime a luxury when you got more than one target.
If there is no way around it - I will STACK,specially if it's tighter load.
DaveW-I wonder if Hornady may have them "duplex loads" compressed using bulky powders to keep them STACKED if needed. Some one shoud shake them cartridges and hear if powder moves in them.
olegburn

[sw]

Oct 22, 2010 9:07:16 GMT -5 olegburn said:

If there is no way around it - I will STACK,specially if it's tighter load.
DaveW-I wonder if Hornady may have them "duplex loads" compressed using bulky powders to keep them STACKED if needed. Some one shoud shake them cartridges and hear if powder moves in them.
olegburn

I don't know about the Heavy Mag Hornady charges(I think I remember that they exist) but on the Light Mag cartridges, they seem to be both layered and compressed. I don't know how else they would work either.

[spoonover]

I could find most of this in a search and have, a lot of research? You men have made this sound easy, I think I will have to jump in with both feet.

To keep this going let me throw this out please? Before I practice duplex please point out my errors, I am just guessing.

Have seen duplex loads (less gas ejecta?) that generate more speed and less recoil than single powder loads on some of the posts. Is this because slower burn powders loaded signal have more ejecta than when added with a duplex?

In the Savage .50 with a 250 grain 4759 45 grain load is mild. Can a duplex render more speed with less felt recoil or close? Realizing ejecta of the 4759 is probably nil (14" optimal burn) and increase bullet speed will have a price.

[Harley]

Harley wrote, "P.S.: DaveW's comparison (Reply #10, above), while only one group, is good enough for me."

Edge replied, "Hmmm....... IMO, that is not enough for me!"

Edge, what I was sloppily trying to say was that I am satisfied with my stacked load, which averages about one-half inch at 100 yards; and that the comparison group, no matter what its size, wouldn't have impressed me enough to change.

I absolutely agree with you on evaluating in general.

Harley

[Dave W]

Oct 22, 2010 9:21:42 GMT -5 spoonover said:

I could find most of this in a search and have, a lot of research? You men have made this sound easy, I think I will have to jump in with both feet.

To keep this going let me throw this out please? Before I practice duplex please point out my errors, I am just guessing.

Have seen duplex loads (less gas ejecta?) that generate more speed and less recoil than single powder loads on some of the posts. Is this because slower burn powders loaded signal have more ejecta than when added with a duplex?

In the Savage .50 with a 250 grain 4759 45 grain load is mild. Can a duplex render more speed with less felt recoil or close? Realizing ejecta of the 4759 is probably nil (14" optimal burn) and increase bullet speed will have a price.

Slow powders need barrel length to burn efficiently since we are not getting the big pressure spike when the bullet jumps into the lands like in a cartridge rifle. The way to overcome inefficiency of a slow powder is to boost it, otherwise you get to a point where the velocity does not increase as much as it should when the charge weight is increased, you will likely see a lot of excess muzzle flash also.


With speed comes recoil, no way around it other than recoil reducers or added weight in the stock.

[rbinar]

Oct 22, 2010 9:21:42 GMT -5 spoonover said:

I could find most of this in a search and have, a lot of research? You men have made this sound easy, I think I will have to jump in with both feet.

To keep this going let me throw this out please? Before I practice duplex please point out my errors, I am just guessing.

Have seen duplex loads (less gas ejecta?) that generate more speed and less recoil than single powder loads on some of the posts. Is this because slower burn powders loaded signal have more ejecta than when added with a duplex?

In the Savage .50 with a 250 grain 4759 45 grain load is mild. Can a duplex render more speed with less felt recoil or close? Realizing ejecta of the 4759 is probably nil (14" optimal burn) and increase bullet speed will have a price.

If you go to duplex it's a good idea to know what to expect. Following comments are for 50 caliber duplex. You will not reduce recoil unless you are already shooting a slow single that requires a lot of powder to get to speed.

What you can get is appreciable more speed in the 2550 to 2800fps (even faster possible but deadly recoil) with a 250 grain bullet. The speed can be had with accuracy because duplex allows adjusting pressure to optimum levels for any given amount of powder. To accomplish this however the load needs to be well produced for your requirements.

I cannot guide you on an exact load but there should be many around here who can point you to a proven starting point and tuning process.

In the past loads were a bit heavy. One that was a popular shot 75 grains total: with N110 under H322. I can say that was probably too much powder for the common speed reached. You may notice I have to be careful in exact wording, but I could mention that more than 70 grains seems over kill or too low a pressure whichever comes first.

Anyway before my foot goes firmly in mouth let me just say you can get great advice from the sources already here.

[sw]

RB, the originator of the 14/61 VV-110/H-322, himself refined this duplex to 19-21/51-49 to get a better pressure load as the 1st one was a little pressure starved. Many of us had already moved to the 45s by the time he made this change. RB may want to elaborate or correct.

[olegburn]

What is pressure starved?
How it manifests?

[rbinar]

Oct 22, 2010 22:34:33 GMT -5 olegburn said:

What is pressure starved?
How it manifests?

It may never be manifest in certain conditions. For instance the load SW mentions with 75 grains total N110 under H322 may work here in South Arkansas or East Texas forever with no signs of low pressure.

In some Northern areas that may not be the case. When temperatures plummet so may the load if it is not up to minimum pressure. It's hard to talk about low pressure because one never wants a shooter to reason that high pressure can be totally disregarded. If you take a great big step and go from low pressure to high pressure then you'd be better off not stepping.

However modern sabots can take some pressure and for best over all performance sticking to a moderate or even slightly higher pressure will work in the greatest number of circumstances. There is less likelihood of temperature sensitivity and accuracy degradation in varying conditions.

Basically pressure starvation isn't a basic problem of loads but it is a condition found in the 50 caliber 10ML because a uniquely light weight (say 263 grains) bullet is being shot from a massive smokeless rifle bore. The bigger the bore the harder it is to make pressure within the powder speeds normally associated with a rifle.

Without starting a move toward high pressure loads, I'd say 75 grains of powder shooting a 263 grain bullet to only 2650fps (did he say only) is too much. That speed should occur at lesser load levels with the same weight bullet if loads are to meet a minimum pressure.

So I guess I just said if you're shooting a bunch of powder and the speed for a very light weight bullet is not up to shoulder rendering recoil then that might be a sign of pressure starvation. Yet, that would be misleading for there's more to it than simply raising pressure. Starting this process at a point where pressure is on a thresh hold would be a bad thing. What is a thresh hold? Well if you don't already know perhaps putting a lot of powder to test a big bore might not be the best thing.

However the load mentioned was not near a thresh hold it was simply a lot of powder for the speed it reached. So moving to slightly more booster and less primary to shoot the same speed was sensible in this case. The newer load shoots higher pressure to about the same or greater bullet speed, but still is well under the disruption level of most sabots, so it's likely more stable in different circumstances.

[olegburn]

RB,thanks for weighing-in on this!
I'm educating myself on Duplexing before I get into it.
Technical part of it is where I can only rely on this forums experience.
WHile weather is mild I may still have some time to prepare.
Single H4198 ignites OK now and I'm enjoying its accuracy.Hopefully by the time temps drop I will have new load,otherwise I will have to fall back on 4759 as did last year.
Oleg