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Powder burnt % question

jfjohn77

Silver $$ Contributor
Can someone shed a little more light on my knowledge of the percentage of powder burnt before the bullet leaves the barrel? I realize (or at least I think I do) that 100% is ideal, and should be the goal. But, as the percentage decreases, at what point does it start to become detrimental? To me, if you have unburnt particles of powder exiting the barrel at a faster velocity than the bullet itself, it would have to have some impact (pun intended) on the bullet's stability and/or flight path. Or am I overthinking this?
 
Can someone shed a little more light on my knowledge of the percentage of powder burnt before the bullet leaves the barrel? I realize (or at least I think I do) that 100% is ideal, and should be the goal. But, as the percentage decreases, at what point does it start to become detrimental? To me, if you have unburnt particles of powder exiting the barrel at a faster velocity than the bullet itself, it would have to have some impact (pun intended) on the bullet's stability and/or flight path. Or am I overthinking this?
Believe the target.
 
Your understanding is correct. The unburnt particles can impact the base/boat tail of the bullet which can imparts yawing motion on the bullet.
 
My whole answer here is just an opinion, not facts.

The only problem we have, is an administration that is so anti that the investment for ballistic science (really all science) has suffered from a lack of investment. Long way of saying the comments are anecdotal and not quantitative or on solid ground experimentally. The scope of the research required to pull off a solid study would exceed the commercial investors abilities.

(If I put words in quotes, it is for a good reason. Unless someone measures something and can prove it, these words are relative and have no dimensions.)

In several of our "best" systems, there is a "significant" amount of unburnt powder going out the muzzle. We have learned this several generations ago, even going back to wet film processing and long before cheap digital high speed was available.

Now that we have proliferated cheap high speed digital cameras, how we can "see" is better and cheaper, but that doesn't mean we can say anything else. Playing with propellant specs and designs is very expensive and gets political real quick.

It will take a solid research program at one of the national labs and as far as I know that hasn't happened. Keep in mind, our direct and indirect artillery is also affected and I don't want to tell you how much unburnt powder goes out the muzzle on the big guns. That said, our "best" systems do this all the time but who can say if it would be "better" were it not being pushed with a stream of those solids?
 
I wonder if a momentum vs muzzle velocity test (charge plus projectile) would show max burnt, leftover powder with a ladder test?

Unburnt being part of the initial charge weight, but not adding to velocity?
 
I wonder if a momentum test (charge plus projectile) would show max burnt, leftover powder with a ladder test?
It ends up inconclusive. If you think about accuracy tuning, there are almost as many examples of %burn on the ones that work best as the ones that don't.

It would take proving the %unburnt was the cause, and that can vary for boattails and flat base even with 100% burnt. With so many 120mm cannons that use sabot style rounds, it taught me you can't always have your cake and eat it too.

My only advice is to trust the targets and not go too crazy with the keyboards and models.
 
If you want to see how much powder is unburnt shoot through a piece of white corrugated placed about 5-7' in front of the muzzle.
 
And then everything changes if you are shooting a gas operated and or suppressed gun.

Unburned or partially burned powder can stay in the chamber and cause feeding problems, but that is fairly rare. You’re more likely to have problems with a trigger group. Those would be considered detrimental.

You’re more likely to just have an unpleasant experience with too slow of a powder sitting in a cloud of smoke while you shoot, because as much blows back out of the breech end as the muzzle.

Shooting in low light or indoor ranges, with slow for application powders is kind of fun if you enjoy fire balls. And in general the more you burn inside the barrel, the quieter the muzzle blast will be.

Just some other things that people are looking for in 100% burn.
 
I look at it like an engine. An engine has hiding spaces that will always trap fuel and this makes it different than a cartridge and barrel. I load powders that have predictions of burnout before muzzle exit to 1 use as little powder as needed to reach the velocity and accuracy as possible. 2 because the ignition of the powders can be inconsistent and as long as it’s supposed to be burnt out before exit I’ve at least got a better chance of a consistent burn than blowing different amounts out the muzzle. I don’t know if my process is optimum or not but since I got the software to analyze my loads before I pour powder my guns shoot better. I realized that the burn rate chart was less important and running loads on the computer was free. Then I take what I find and load and shoot.
 
I have run into this situation at least twice that I am aware of. On each occasion I was using a firearm with a shorter barrel than what the load was developed on. On both occasions I felt my face being pelted with unburnt or then burning powder. I ended up using a faster burning powder to create the same result without getting the burning sensation on my face. Basically using a practical solution to the problem without giving it allot of thought.

Mike
 
So you wouldn't google that and read some of the hundreds if not thousands of papers written on the subject?
 
Can someone shed a little more light on my knowledge of the percentage of powder burnt before the bullet leaves the barrel? I realize (or at least I think I do) that 100% is ideal, and should be the goal. But, as the percentage decreases, at what point does it start to become detrimental? To me, if you have unburnt particles of powder exiting the barrel at a faster velocity than the bullet itself, it would have to have some impact (pun intended) on the bullet's stability and/or flight path. Or am I overthinking this?
I use quick load and GRT to get my estimates of % powder burnt. The following is only based on my personal experiences... Through actual results that I see on target.

The larger the % (estimated by software) of unburnt powder, tells me that the powder is less suitable for the cartridge, bullet and COAL. But I'm personally okay with a bit of unburnt powder. I'll give the load combination a try. Remember, this software is just an estimation, so you might end up with less unburnt powder.

I have found through my own testing that any load with an estimated powder burnt of less than 92% really isn't worth trying. Unless you have no other options. At least this is the case for full power loads. And for jacketed loads.

More importantly to me, I am looking at powder burn % along with case fill %. I sometimes give a 85% case fill a try if the powder is 100% burned. Like when using faster rifle powders in case with large capacity. But if I have 85% fill and 92% burn, I will always try a different combination first.

One last thought, I do not have experience on how these %s need to be addressed and analyzed if you are making bench rest comp loads. I imagine that introduces a whole extra set of variables and requirements to your end result.
 
I use quick load and GRT to get my estimates of % powder burnt. The following is only based on my personal experiences... Through actual results that I see on target.

The larger the % (estimated by software) of unburnt powder, tells me that the powder is less suitable for the cartridge, bullet and COAL. But I'm personally okay with a bit of unburnt powder. I'll give the load combination a try. Remember, this software is just an estimation, so you might end up with less unburnt powder.

I have found through my own testing that any load with an estimated powder burnt of less than 92% really isn't worth trying. Unless you have no other options. At least this is the case for full power loads. And for jacketed loads.

More importantly to me, I am looking at powder burn % along with case fill %. I sometimes give a 85% case fill a try if the powder is 100% burned. Like when using faster rifle powders in case with large capacity. But if I have 85% fill and 92% burn, I will always try a different combination first.

One last thought, I do not have experience on how these %s need to be addressed and analyzed if you are making bench rest comp loads. I imagine that introduces a whole extra set of variables and requirements to your end result.
I also use GRT, although admittedly I'm new to the software. And yes I understand and agree with what you just stated. I look for 100% powder burn and loads above 94% load ratio. Again, as you said, these are best estimates according to the software with the information you feed it. But it is my guidelines for searching for appropriate powders. I only asked the above question because I hoped someone with more knowledge and/or experience could shed more light on my thinking. Especially regarding at what point below my targeted percentages, accuracy is diminished. Short of checking at the range. After all, isn't the whole point of using software... to save range time and components.
 
I also use GRT, although admittedly I'm new to the software. And yes I understand and agree with what you just stated. I look for 100% powder burn and loads above 94% load ratio. Again, as you said, these are best estimates according to the software with the information you feed it. But it is my guidelines for searching for appropriate powders. I only asked the above question because I hoped someone with more knowledge and/or experience could shed more light on my thinking. Especially regarding at what point below my targeted percentages, accuracy is diminished. Short of checking at the range. After all, isn't the whole point of using software... to save range time and components.
Totally understand. I do the same things when looking for an appropriate powder to try. I wish there was a way to know more about the science behind it. I forgot to add one item though. Extruded powders are much more forgiving with unburnt and fill percentages than spherical powder. I don't think I have had good luck with spherical below 94%fill and 98% burnt.
 
I have also "read" that single base powders for the most part, tend to be more accurate than double base once you find the node. But, I can't speak to the validity of that statement.
 
As for % Unburnt I tend to agree with @RegionRat. It ultimately is probably a tradeoff of velocity versus accuracy/precision. But there are other issues that come into play other than just effect on bullet flight. On of the first things I observed when I tried 2000MR in my 308 was that to achieve comparable velocity to IMR 4064 I needed about 3-4gn additional powder to get the same velocity and the 20" barrel had enormous muzzle flash and noticeably more recoil. Based on its burn rate I suspect it has a lot more unburnt powder than the 4064.

As to extruded versus spherical powders. If you look at competitive shooters there is a definite preference for single based extruded powders over spherical double based powders. Historically they have had better performance and are less temperature sensitive which helped minimize one aspect of shot dispersion and can simplify reloading. Not all extruded powders are single based. In particular Reloader 15, IMR Enduron, and the new 500 series of Vihtavouri powders are extruded. Anecdotally this would support that single based extruded powders are more accurate but it doesn't necessarily mean that a double based spherical powder can't/won't be as accurate and I would seriously question any study that reached that conclusion. Those powders may simply be more difficult to mange repeatable performance.

@Laurie probably has the best handle on this with all of his testing on powders.
 
I have also "read" that single base powders for the most part, tend to be more accurate than double base once you find the node. But, I can't speak to the validity of that statement.
Do you really think that bench rest shooters shooting consistant groups about 0.200" or smaller worry about the % powder burn. You develope loads to shoot small groups not to reduce unburned powder.
 

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