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Post by boolitdesigner on May 30, 2017 17:30:53 GMT -5
I've read a lot of old articles about the old black powder guys triplexing different speeds and grades of black powder, so I would expect the early smokeless guys did the same though I never read much about that. I get mostly harassment from people when I talk about duplexing, mostly about how dangerous it is mixing powders..... the problem with that is you don't mix powders, you layer them. Intelligent conversation about duplexing doesn't seem to exist from the younger generation............
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Post by sixshot on May 30, 2017 20:27:08 GMT -5
You are absolutely right, the powder is layered so it can't "migrate" into the other powder & mix burning rates. As you mentioned it's kind of a lost art in most circles, kind of "voodoo" to many. I'll bet David Bradshaw at least experimented with it in the early days of the 357 Maximum with that long powder column, it would be the perfect example of why a person would try a duplex load. An example would be Bullseye or Unique on the bottom, next to the primer, followed by the slower powders which could be 4227, H110, 296 (same thing) AA9, Lil Gun or even RL7 as long as the bullet touched the powder enough to compress it slightly to keep it from "migrating". Another example would be the 444 Marlin case.
Dick
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Post by cherokeetracker on May 31, 2017 21:59:17 GMT -5
Fermin and a few others, have talked about this a little, with me. But I have never been sure just how much of each powder to go with. While I do understand that you must layer the powders and get the full case capacity, so that once the bullet is seated the powder will not move and mix. Is there a rule of thumb with this? By that I mean is there a rule of how much of a faster powder is usually placed in the case before the slower burning powder? I can see in real cold weather how this might be quite handy, with some powders that are more difficult to ignite.
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Post by boolitdesigner on May 31, 2017 22:04:24 GMT -5
There are rules.... but they depend on caliber, straight case, bottle neck case, CARTRIDGE CAPACITY, projectile weight, speed wanted. It varies with the preceding items. It isn't just what you think it is either.
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Post by bradshaw on Jun 1, 2017 0:37:43 GMT -5
Dave Ingram of Arizona was an early silhouetter and early hotrodder of the T/C Contender. Ingram’s duplex powder charges turned the tip-open single shot into an auto ejector. I’m not going to advocate duplex loading. It is known in blasting that a booster charge accelerates a column of slower explosive (lower VOD----Velocity of Detonation). Yet the lower velocity powder----now boosted----does not sustain the higher velocity; the slower powder comes back down. To simplify, lower velocity produces HEAVE; high velocity produces SHATTER. Note: handloaders call their propellant “powder,” and blasters call dynamite “powder.”
I think that there is a similar burn acceleration characteristic between smokeless powder and high explosive. Which is, for the velocity of a boosted charge to accelerate and then slow. However, despite the vastly slower velocity of smokeless, its minuscule charge is consumed before main charge deceleration sets in. The effect of a smokeless booster is to increase energy. The effect of an explosives booster is ti insure ignition. David Bradshaw
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Post by cherokeetracker on Jun 1, 2017 14:33:21 GMT -5
There are rules.... but they depend on caliber, straight case, bottle neck case, CARTRIDGE CAPACITY, projectile weight, speed wanted. It varies with the preceding items. It isn't just what you think it is either. The effect of an explosives booster is to insure ignition. What David said ,,, This is what I was thinking about when I was thinking cold weather ignition. Is this wrong? I am completely in the Dark on this, but would not mind having a little light shed on me. I doubt I would ever want to use a duplex load, But what David said would be what I was thinking in terms of, can I say " jump Starting a slower burning powder" ? Thanks Bob ( I believe that's your name) for the rules of thumb. Was or was not the intention of some folks, to get the velocity without the higher pressures? In say the 454 or some instances that I am not aware of.. Bob, it was mentioned, using a duplex load with the 5.56, and the lead bullets. What is the specific reason for this? or can you explain the benefits? might be a better way to put it.
Charles
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Post by boolitdesigner on Jun 1, 2017 18:08:36 GMT -5
There are rules.... but they depend on caliber, straight case, bottle neck case, CARTRIDGE CAPACITY, projectile weight, speed wanted. It varies with the preceding items. It isn't just what you think it is either. The effect of an explosives booster is to insure ignition. What David said ,,, This is what I was thinking about when I was thinking cold weather ignition. Is this wrong? Yes, it is incorrect.... you are dealing with projectile propellant (and defined as such), not explosives. I am completely in the Dark on this, but would not mind having a little light shed on me. As I deal with duplexing, I use a powder that would be classified as "too slow for the cartridge", use a booster charge to get it to burn like a very slow powder for the cartridge which will give it a longer milder pressure curve which benefits accuracy and barrel life along with almost no muzzle flash at night. In a small cartridge it works somewhat poorly because you really don't have enough room for powder... in a big cartridge you will be tasked to find a powder that is too slow for it to work (a poor example of this was posted on cast boolits, please don't try it like that). I doubt I would ever want to use a duplex load, But what David said would be what I was thinking in terms of, can I say " jump Starting a slower burning powder" ? A good example is the 308 Win/7.62x51 Nato..... I use Surplus 867 (bought at about $5.50/Lb.) and boost it with a faster rifle powder which pushes a 180 GC cast bullet to about 2,400 fps dependent on how long a barrel it is shot in. This particular combination parallels 4350 exactly for total powder weight and velocity. Accuracy runs from 5/8 MOA to 1.25 MOA in different rifles (some of those rifles are rated with poorer accuracy by the manufacturer than what I got... a bonus!).... it shoots the same size groups with jacketed substituted also. Economical when you shoot long range.
Thanks Bob ( I believe that's your name) for the rules of thumb. They weren't so much rules as guidelines that depend on what you choose to do.
Was or was not the intention of some folks, to get the velocity without the higher pressures? In say the 454 or some instances that I am not aware of.. Since I'm not them, I can't say what they intended, but a Contender self ejecting should be a good warning sign things aren't well. I duplex cartridges from the 222 Rem up to about the 375 H&H getting proper sight regulation and excellent accuracy without ANY problems....... I have read otherwise and those people really need to learn more from someone who knows what they are doing.
Bob, it was mentioned, using a duplex load with the 5.56, and the lead bullets. What is the specific reason for this? Boredom with too easy of things to do or increasing my knowledge of the subject along with being able to use just about anything to achieve my purpose. or can you explain the benefits? might be a better way to put it. To keep shooting while others are down from not being able to find the powders (or something they know about) to keep shooting.
Charles
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Post by dougader on Jun 2, 2017 17:54:07 GMT -5
My hardness tester says about 19 BHN. Duplexing seems to bring out the nay-sayers in abundance. I've been doing so for the last 30 or so years with excellent results and very cheap shooting. I stared using duplex loads, AA4350 over Blue Dot, to use up some AA4350 that was starting to show signs of aging. I used around 5 grains Blue Dot and then covered it up with AA4350 in my 30/30 loads for use in my TC contender. Great plinking loads and no problems with pressure signs at all.
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Post by sixshot on Jun 3, 2017 12:50:34 GMT -5
While I've read about duplex loads for many years & know that many shooters have used them with great success I have to admit to never trying any myself, although I know it can be done safely & effectively. I do wish more people would talk about their results doing it but almost always it's just cast bullet shooters that seem to be in that circle.
Dick
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Post by contender on Jun 3, 2017 21:51:07 GMT -5
I was re-reading an old G&A from 1968 or early 1969. Elmer mentions duplex loads in one of his articles, kinda casually.
Like Dick,,, I came have never experimented with duplex loads. My reloading hobby got started in about 1977. And,, I was careful & stuck to the manuals, even though my reading & education allowed me to know about them. I can see where they may have merit in some applications.
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snappy
.30 Stingray
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Post by snappy on Jun 3, 2017 22:32:28 GMT -5
Interesting stuff. So do triplex loads just add an additional stage of "boosting" as discussed above? It's pretty amazing to contemplate all that goes on in that instant the shot breaks.
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Post by sixshot on Jun 4, 2017 0:15:03 GMT -5
Yes, as far as I know. Some even experimented with a stem that was attached from the primer up to the front of the powder column & ignited the front of the powder first & then burned back if I remember correctly. Some others might remember this & chime in.
Dick
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jwp475
.375 Atomic
Posts: 1,084
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Post by jwp475 on Jun 4, 2017 4:58:15 GMT -5
Yes, as far as I know. Some even experimented with a stem that was attached from the primer up to the front of the powder column & ignited the front of the powder first & then burned back if I remember correctly. Some others might remember this & chime in. Dick Frontal ignition, there were some long range shooters a few years back that were doing this. The tube was threaded into the case head, they claimed reduced barrel heat, if memory serves.
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Post by cherokeetracker on Jun 5, 2017 7:10:35 GMT -5
Yes, as far as I know. Some even experimented with a stem that was attached from the primer up to the front of the powder column & ignited the front of the powder first & then burned back if I remember correctly. Some others might remember this & chime in. Dick Frontal ignition, there were some long range shooters a few years back that were doing this. The tube was threaded into the case head, they claimed reduced barrel heat, if memory serves. I have heard of this (frontal ignition) also. also,, I have heard that some Benchrest shooters have used duplex loads. I can't say for sure one way or another.
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Post by sixshot on Jun 5, 2017 11:49:59 GMT -5
cherokeetracker, I forgot to mention earlier when you first mentioned about heat treating your bullets in the toaster oven & then not getting them all sized for a couple of weeks & then you stated how hard they were to size. The easy way to correct that besides spraying with Hornady One Shot, which doesn't always solved the problem after they've set for several days is, just reheat them again in the toaster oven. That solves the hardness problem & lets you start over & it doesn't change anything. Sorry for not mentioning this before!
Dick
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