Curiosity .... not intention

[Vacek]

I am just curious here and am not planning anything. IMR 4350 and IMR 4831 are similar in many aspects. What would happen if the two were mixed with about 80% 4831 and 20% 4350?

Again, not to do this but to understand what would supposedly happen if two similar powders were mixed.

 

[longdayjake]

Probably not much, but remember that anytime you start mixing powders you may change the burn rate and even if they are similar in burn rate, you may end up getting something totally unexpected.

 

[kingmt]

My best guess:
1st possibility is nothing drastic because they are close in burn rate.

2nd possibility is you get a burn rate somewhere between the 2.

3rd & worst is that you get a powder that becomes spikey before you get to the load your working on.(No pressure signs. No pressure signs. Oh crap what was that?)

 

[GLOOB]

4th possibility is you make an amazing powder that achieves one hole groups at 100 yards!?

 

[RandyP]

Blending powders presents the potential for catastophe. Not a guaranteed disaster, but certainly the potential for one. Once a reloader goes totally 'off the charts' it is difficult to create a safe test environment.

As such, it is not worth the risk. It is so much easier to simply experiment with different published and proven load data 'recipes'.

 

[ranger335v]

"Blending" powders has been a smokey dream of a lot of half-baked reloaders ever since smokeless has been available and some have actually tried it. Those who live still give it up.

 

[ArchAngelCD]

"Blending" powders has been a smokey dream of a lot of half-baked reloaders ever since smokeless has been available and some have actually tried it. Those who live still give it up.

Well said, I couldn't agree more...

 

[RandyP]

To quote the venerable Mrs. Gump - "Stupid is as stupid does."

 

[kingmt]

I wouldn't say it's stupid. Many factory loads are from blended powder. Even some of the canister grades are blended.

 

[Mal H]

The funny thing about nitro... is the way it works under pressure. You can witness the effect yourself every time you fire a cartridge. Take that same amount of powder and ignite it outside of a pressure containment vessel (namely a case), and it burns very slowly in comparison. The same is true of almost any nitro compound. We all know that dynamite explodes when subjected to a sharp impact (usually from a blasting cap), but simply throw a stick in a fire and all it does is burn with quite a hot flame, but it only burns.

My point being that you cannot predict what the pressure inside the case will be with a mixture of two different powders. You can only get empirical data from the actual firing of the mixture. Powder companies and ammo manufacturers have the facilities and instruments to carry out such experiments, most home reloaders don't.

Having said all that, the two powders mentioned are close to each other in both burn rate and, perhaps more importantly for this discussion, grain shape. My best guess with the two powders mentioned is that it would act more like 4831 than 4350 and would have a slightly faster burn rate.

 

[tightgroup tiger]

MalH
I'm glad you said that, it saved me from having to type it all out. Even though the burn rate is very close the faster could spike the slower one. I'll never know though.

 

[ranger335v]

"I wouldn't say it's stupid. Many factory loads are from blended powder. Even some of the canister grades are blended."

Absolutely true. And, as soon as I can get me a proper 'closed bomb' test chamber and all the required gadgets to observe what happens and measure the pressures produced and learn how to interpret all that info I'm sure gonna try it. But, for now and for me, it would be really stupid to attempt blending any different types of powder and I've been doing this reloading stuff for pushing five decades without so much as a case head seperation.

 

[HankB]

An argument can be made for individual handloaders blending different lots of the same exact cannister powder, but blending different powders may give unexpectedly different results.

I suspect blending single base IMR powders like 4350 and 4831 would give results somewhere between the two . . . but I most certainly am NOT going to be the one to do it.

As for factory loads using blended powder . . . I believe they blend different lots of the same powder. Powders vary quite a bit from lot to lot, and cannister grade powders - those you and I buy at the store - are chosen so that variability falls within a fairly narrow range. What do manufacturers do with powder OUTSIDE the "standard" range? Well, they either adjust the powder charge in the ammo they're loading to compensate, or they blend different lots of the powder, mixing "slow" with "fast" to get the desired "medium" burn rate.

Their blending methods and formulas are probably highly proprietary, closely held trade secrets, and backed up with instrumentation most of us simply don't have access to.

 

[GaryL]

A friend (chemical engineer) with experience in the pharmaceutical industry tells me it is notoriously difficult to uniformly blend two different dry powders. I have no reason to doubt that. So for purposes of discussion, I'd be worried about working up a load that is primarily one powder, and getting some loads that are primarily the other. I really don't think it would be the best method for developing an accurate load.

Taking a step back, I have to ask "what is the point"? Most cartridges have a dozen or more powders available that will work, so any reloader could go through all the available choices to find what works best for them.

 

[JimKirk]

What would you get .... IMR 4735 .... a for sure non canister powder. Just joking !

But you can best belive that IMR has tested at least some mixture trying to great a results that they needed. But they have the equipment to find out for sure.

Jimmy K

 

[Frozen North]

Even daring loaders stay away from duplex loads for a reason. It really offers no advantage because it would be very difficult to precisely blend the powders and then duplicate the process in the future. I suppose you could stack the powder in the case, but that would seem to open a new can of worms.

We all know that the name of the game in accuracy is consistency and reliable duplication.

It would be like introducing your two girlfriends to each other and taking them both on a date. The outcome could be amazing, but you are much, much more likely to end up with a black eye and a missing tooth!

 

[PO2Hammer]

Wouldn't the powders tend to separate over time from vibrations unless they have the exact same size, shape and density?

 

[Frozen North]

You would sure think so... Physics are physics...

 

[blarby]

Unfortunately, breaking down the pressure curve per grain of each of the powders in the presence of the other would be both a long and dangerous task.

More long in the beginning, and much more dangerous towards the end....Don't think thats justifies the means...but hey- they aren't my fingers !

"A friend (chemical engineer) with experience in the pharmaceutical industry tells me it is notoriously difficult to uniformly blend two different dry powders. I have no reason to doubt that."​

Nor do I, thats part of the difficulty. You would have to weigh out each individual round one at a time. You could not bulk mix them accurately.

Impossible... no. Anything is possible given time, equipment, and desire. Remember- helicopters don't fly on paper... Someone had to build one that worked to show all those crazy "forum-jockeys" of the past that he was right.

However

"It would be like introducing your two girlfriends to each other and taking them both on a date. The outcome could be amazing, but you are much, much more likely to end up with a black eye and a missing tooth! "​

Probably sums up most of the max load end results quite nicely.

Lots of injuries in that helicopter path, too.

 

[RandyP]

So...Vacek?

Is your curiosity abated? - lol

 

[kingmt]

As for factory loads using blended powder . . . I believe they blend different lots of the same powder

I don't work for these factories & can only go on what they have told me & what I have found from pull downs. I have seen different shapes & sizes of powders in the same case. One of the manufactures has told me that they do some experimenting by blending in house.

I was also told by a powder company(after I ask them about it) that they bought pulled down powder tested it then blended it with other powder(even new production) to get the correct burn rate to repackage in canister form. There reason was that there is a powder shortage & this is how they keep price down. I was told there was no way enough powder could be produced for the military & privet sale. I see no reason for them to lie to me seeing how they was reluctant to give me a answer until I told them my source of the info.

I'm in no way suggesting anyone try this. I agree that it isn't worth the time or risk. Powder is hard to mix correctly & would be likely faster on one load then an other.

It was said to put one load on top of the other. This isn't blending. It is a detonating charge which is used to raise the pressure fast enough to allow the slower powder to burn. This creates a controlled spike. It is also more dangerous then blending. Please don't try this unless you want to lose a gun, eye, & probably worst.