Combustion efficiency, muzzle pressure, velocity, accuracy and other odds and ends

[dcali]

I don't have much to say on this topic, but it's been rattling around in my brain for a while. The central question is:

"What makes a good powder a good powder for a given rifle/cartridge?"

QuikLOAD gives us some insight, but not an answer. We can see muzzle pressure, the percentage of powder burned, and when that happens, the resulting muzzle velocity. But not the most important part- which one is going to shoot the best.

So what does the mob think? Is there a way to intelligently select a powder other than "use what everyone else uses" or "just randomly test them"?

How would you go about choosing a powder if you couldn't ask your friends and *why*?

 

[Twoboxer]

With no other input available, the first powder(s) I'd try are those showing the highest "max" velocity in load books with the bullet I'm using, ideally without compression.

 

[Ned Ludd]

In my hands, there are several factors that seem to be common amongst powders that seem to work well in a given setup. First, you want the case fill ratio to be in the ~95-103% range within the accuracy window you have chosen. Second, I have always found that powders slightly toward the faster end of the scale seem to give better results that at the slower end. Third, I've also had better results with powders that have slightly smaller kernel sizes. Bear in mind that I exclusively use single base powders. Further, I have already determined the barrel length and twist rate that is appropriate for the given bullet I'm loading. I'm not claiming that if you do these things you are "guaranteed" to proceed a good load. However, they are factors that time and time again seem to coincide between successful loads I have developed over a range of different calibers/bullets. My take is that they are likely contributors to optimal combustion efficiency and ultimately, performance.

 

[gunsandgunsmithing]

The biggest factor to proper powder choices are case capacity to bore ratio and bullet weight. These two things alone, will put you in the right "range" of powders. From there, all the typical reloading rules seem to apply for accuracy. Such as, fill rate, velocity and muzzle pressure...which all may or may not actually contribute to accuracy, but I think most will agree that they are important factors. I'e., a 30br vs a 22 or 6br, with equal bullet weight. The larger bore needs a faster powder to build pressure in the time it has to work. I'm referring to "expansion area" here. A good way to look at this is, a point say 5 inches in front of the bolt face of a 30 cal BR chamber will have significantly more volume than a 6BR, due to the larger bore. The larger expansion area will require a faster powder to build the pressure to the same level, in the same distance.

 

[mikecr]

Fastest powder that fills the case at SAAMI max pressure. This should burn up in the bore, and providing lower muzzle pressure.
Of multiple powders meeting this, I go with the coolest burning for more barrel life.

 

[Uncle Ed]

In the movie "Easy Rider" Dennis Hopper says "I'm getting bad vibes man, I'm getting bad vibes".

And barrel vibrations are your "bad vibes" when looking for the "node".

There are two ways to tune a rifle, tune the rifle to issued ammunition like the military or tune the ammo to the rifle.

I node you all would understand. (even F. Guffey knows this)

 

[dcali]

I know that tuning a rifle is required. What I’m more interested in is why, if two similar powders are used, that you can find that one doesn’t shoot well and the other does. For example, in my 6xc, H4350 shoots very well. H4831SC just makes a puff of smoke and lousy groups.

Incidentally, does a puff of smoke imply poor combustion? It’s not something I’ve paid much attention to, but can you *see* when a powder isn’t burning right?i have anecdotally noticed a lot of smoke when my rifles shoot poorly, but that could just be in my head.

Things that make sense to me would be load density, ignition characteristics (not sure how to define that), burn rate in relation to barrel volume/length/caliber, muzzle pressure, maybe flame temperature. Just curious what others look for. I’m lazy, so I’ve always just used what works for other people.

 

[gunsandgunsmithing]

In the movie "Easy Rider" Dennis Hopper says "I'm getting bad vibes man, I'm getting bad vibes".

And barrel vibrations are your "bad vibes" when looking for the "node".

There are two ways to tune a rifle, tune the rifle to issued ammunition like the military or tune the ammo to the rifle.

I node you all would understand. (even F. Guffey knows this)

Barrel vibration is inherent and inevitable. The best we can do is dampen and manage these vibrations in a controllable fashion. Tuning the ammo to the gun is one way to time the vibration with bullet exit, in our favor and is what hand loading is really all about.

Tuners allow us to tune the gun to the ammo. You can tune the combination to its potential but not all loads nor components have equal potential in a given gun, just like not all guns have the same potential. That's why we should find the best load in a given gun before tuning with a tuner. Often, the two do coincide.

Take a 6PPC for example...There are numerous proven good loads that seem to work in a lot of them in a given condition. Those same loads can most always be made to shoot in your gun with just a slight nudge of the tuner. But it will always leave you(me) wondering if I'm leaving anything on the table with the load's potential.

 

[gunsandgunsmithing]

I’m lazy, so I’ve always just used what works for other people.

I'm not lazy but I am hard headed, so what everyone else does is just something else to test for myself.

 

[Pigdog]

I have the same interest that the OP does and have been going through the same kinda path. And I think I have also found what ned ludd says to be spot on at least in my rifle.

I shoot a 6.5x47l with a long freebore .250 with 139 scenars and was originally using H4350 as at 40g it seemed to fill the case relatively well 102.4% according to quickload which is not actually full because I can shake the case and still hear powder slosh around, a quickload user advised me that a proper full case occurs around 106% I believe. Anyway this seemed like the perfect match and it shot fairly well and over the chrono over 13 shots SD of around 8 and ES in the 20's. I ran out of this powder and had Varget sitting there so decided to try that. Did a ladder test found where I wanted to load it etc. The case fill this time is only 94% so in my opinion a much poorer case fill than H4350 however to my surprise the faster varget powder shot with an SD of 4-5 and ES in low teens!!!!! I have reloder 16 still to test and I would like to get some more H4350 just to confirm this but so far the Varget has the lead.

My theory and its just a theory is that like nedd ludd said the fast powder is better possibly cause it burns properly, in my case quickload shows a 100% burn for varget and around 98-99% for H4350 both nodes ended up at very similar pressure according to quickload. However I know some people have had good results with powder not burning to 100% so who knows??? I was surprised by these results and never expected varget to work better than H4350 with the heavier 139 bullets. Varget always worked well with the 123.