Please explain why some powders are more accurate than others

[Chesapeake]

I’m fairly new to reloading and would like to conceptually understand why some powders for a given cartridge and bullet combination could be more accurate than another in a rifle.

I understand that powder A might produce a lower standard deviation or extreme spread of velocity than powder B. I also have seen where powder A could still produce noticably worse groups than powder B. What causes one powder to be more accurate for a certain cartridge bullet combo than another?

This is especially confusing for me when discussing powders of relatively similar burn rates.

Any science bombs you can drop on me would be much appreciated.

I also might have missed this being discussed in my search so if there’s a link please send it. Thanks

 

[_Windrider_]

I’m fairly new to reloading and would like to conceptually understand why some powders for a given cartridge and bullet combination could be more accurate than another in a rifle.

I understand that powder A might produce a lower standard deviation or extreme spread of velocity than powder B. I also have seen where powder A could still produce noticably worse groups than powder B. What causes one powder to be more accurate for a certain cartridge bullet combo than another?

This is especially confusing for me when discussing powders of relatively similar burn rates.

Any science bombs you can drop on me would be much appreciated.

I also might have missed this being discussed in my search so if there’s a link please send it. Thanks

Powder is about burn rate. You want the right burn rate to develop the correct pressure to push the bullet the right speed. That’s why powder selection is caliber dependent. R17 May work with a 308 but not a 6.5 where 4350 is better.

Gotta find the right tool for the job.

 

[_Raining]

Different pressures have different harmonics. Different powders are going to produce different harmonics, even different lots of the same powder can push you out of a node.

 

[Bandit320]

I’ve read some powders are harder on barrels than others, burn temperature of the powder which is different and not directly related to the burn rate. RL-26 gives excellent velocities and good accuracy in both my 243 and 300 WM, but I’ve read it’s one that burns barrels. This should something to think about when selecting a powder. Hopefully someone who has more experience could chime in on that aspect.

 

[Howland]

It's smoke and mirrors. The first one to figure it out will rule the world.

In all seriousness, burn rates have a lot to do with it, as do choice and weight of bullet, primers, case, etc. The mystery is why one combination shoots lights out and another sucks in one rifle with the opposite result in a different rifle.

 

[Chesapeake]

It's smoke and mirrors. The first one to figure it out will rule the world.

In all seriousness, burn rates have a lot to do with it, as do choice and weight of bullet, primers, case, etc. The mystery is why one combination shoots lights out and another sucks in one rifle with the opposite result in a different rifle.

Okay, this is what I thought was true. I just wanted to make sure I was not missing some magic principle.

So what you’re saying is there’s no way to spend less $$ on reloading components?

 

[Deleted member 113831]

I’m fairly new to reloading and would like to conceptually understand why some powders for a given cartridge and bullet combination could be more accurate than another in a rifle.

I understand that powder A might produce a lower standard deviation or extreme spread of velocity than powder B. I also have seen where powder A could still produce noticably worse groups than powder B. What causes one powder to be more accurate for a certain cartridge bullet combo than another?

This is especially confusing for me when discussing powders of relatively similar burn rates.

Any science bombs you can drop on me would be much appreciated.

I also might have missed this being discussed in my search so if there’s a link please send it. Thanks

Two powders of similar burn rate might both be suitable for a certain cartridge. They might even both have the same recommended charge and the same peak pressure. Where they will be different is in the distance from the chamber where that peak pressure happens.

The burn of the powder interacts with the barrel in that it causes the barrel to "whip" like holding a pool noodle at one end and shaking it. It causes the bore to swell and bulge with pressure behind the bullet like blowing a marble through a rubber hose. It causes the bore ahead of the bullet to constrict and dilate like a tube shaped tuning fork. All these things happen at the same time, every single time, you pull the trigger.

Every single barrel (including the chamber) is different. Some are amazingly consistent and forgiving. Some have hidden problems that cause them to favor a single recipe, or even just refuse to shoot anything well. The only way to tell is to try. If your barrel doesn't shoot a particular combination, then don't waste time and components and barrel life on it just because you think that it should shoot.

 

[Deleted member 113831]

Okay, this is what I thought was true. I just wanted to make sure I was not missing some magic principle.

So what you’re saying is there’s no way to spend less $$ on reloading components?

The magic principle is to do load developement efficiently and correctly and do your homework ahead of time:

1) Use the appropriate bullet weight along with the appropriate burn rate.
2) Assemble your loads with care
3) Spend the time on brass prep and rifle prep.
4) Use an efficient load developement method (like OCW)
5) Perform that load dev. method correctly and clearly so that results are easy to see and quantify.
6) If a combo doesn't present a workable load fairly quickly, then try something else.
7) Be honest with yourself about your shooting skills. (Maybe the rifle isn't shooting 1/2 MOA, because you aren't a 1/2 MOA shooter)
8) Verifying a load with multiple groups at distance (at least 200 yards) at the SAME point of aim will show you the loads true potential.

 

[Howland]

Okay, this is what I thought was true. I just wanted to make sure I was not missing some magic principle.

So what you’re saying is there’s no way to spend less $$ on reloading components?

@Skookum made some great points, but I'll add some.

If you got into reloading to save money, well lets just say you'll save as much money as when your wife tried to convince you she "saved" after she found a sale. The plus side is you will get to shoot more.

For each cartridge there is a range of appropriate burn rates. Pick something within that range. If you check out one of the caliber specific threads here, you'll see the same powders mentioned over again and again as someone's pet load. There is a fair chance that will repeat. You don't have to try every powder. Sometimes I'll just pick a powder and develop a load. If I have a couple appropriate powders on hand I might try OCW with more than one.

For each barrel and twist rate there is a range of appropriate bullet weights. Same as with powders, don't venture outside that range.

Then you test with powder charges, bullets, seating depth. There is a good deal of satisfaction when you work up a load that groups tighter than any factory ammo and do it for half the cost* (*=per round after startup costs). We just conveniently forget that we spent enough for twelve boxes of that factory stuff working up the load and if it's a hunting rifle we might shoot 6 or 8 rounds a year. We could however hit the range twice a month just to make it economical. Definitely a good hobby for the OCD type.

 

[spife7980]

There is a good deal of satisfaction when you work up a load that groups tighter than any factory ammo and do it for half the cost* (*=per round after startup costs). We just conveniently forget that we spent enough for twelve boxes of that factory stuff working up the load and if it's a hunting rifle we might shoot 6 or 8 rounds a year. We could however hit the range twice a month just to make it economical. Definitely a good hobby for the OCD type.

The worst part is when you start building rifles or pulling barrels early just to have something new to reload for

 

[Howland]

The worst part is when you start building rifles or pulling barrels early just to have something new to reload for

I'm not there yet but I've gone to the range because I'm out of brass.

 

[Deleted member 113831]

The worst part is when you start building rifles or pulling barrels early just to have something new to reload for

I just posted a full OCW work up for a hunting rifle I haven't shot in years, using random components that I had laying around (none of them especially high quality) just because I was bored.

 

[Holliday]

Well my understanding there are some “goals” to be met when choosing a powder.

Desired velocity
Amount of case that is filled
Optimal barrel time node at desired velocity range
Amount of powder burned in given barrel length
Temperature sensitivity
Availability

 

[Holliday]

I’ve read some powders are harder on barrels than others, burn temperature of the powder which is different and not directly related to the burn rate. RL-26 gives excellent velocities and good accuracy in both my 243 and 300 WM, but I’ve read it’s one that burns barrels. This should something to think about when selecting a powder. Hopefully someone who has more experience could chime in on that aspect.

Dammit, I just settled on RL-26 for my 20 inch 280 Ackley Improved project.....

 

[Bandit320]

Dammit, I just settled on RL-26 for my 20 inch 280 Ackley Improved project.....

View attachment 7071822

I actually really like RL-26, I just read over on the Bolt Action forum a post we’re they claim it’s hard or barrels. I haven’t read a definite study on this, but I’m getting this impression.

 

[ken4570tc in WY]

If your cartridge is commonly used in long range competitions, another consideration for finding a good choice of powder to start with, is to check match results for the list of components. They sometimes list the powders and bullets of the top shooters for the match.

 

[_Raining]

The worst part is when you start building rifles or pulling barrels early just to have something new to reload for

I have no idea what you are talking about. I swapped my 6.5 Creedmoor barrel out for 6 Dasher because the 6.5 Creedmoor barrel was going bad. It wasn't throwing fliers or changing velocity but it was about to, I could feel it in my bones. And OBVIOUSLY you don't want to have the barrel go bad during a competition (That I don't go to) so it just seems smart to switch calibers now.

 

[Milo 2.5]

I personally think if it is in a manual for the bullet selection, with enough resources, time, money, blah, blah, you can get any combo to work to a degree.
I also feel today the path of least resistance is taken quite a bit, there are indeed known powders that work. So it makes it easier to abandon a half assed try to just go to Varget, H4350, H1000, etc... And also, with so much at our fingertips concerning loads, why would one venture out of the box as long as powders are in supply.

Not giving my opinions on this method, but H4350 is the quintessential powder for load development using velocity ladder tests, looking for flat spots. Trying the same with RL 16 &17, VV N540 & 550, you will never see one if 2 shots are fired.

 

[FLIGHT762]

Why was that Redhead a better fuck than the Brunette?

 

[Struggle]

Why was that Redhead a better fuck than the Brunette?

Red was crazy....

 

[Holliday]

Red was crazy....

Fire in the hole!! ?

 

[Ol' RD]

Here is a 10 round speed test with RL17 and 130gr Nosler RDF in a 6.5CM. As you see, I have 3 rounds that are flat yet represent a .4gr spread of powder in the velocity I’m looking for. 43.5 grains makes this easy, just throw and go. A 10th either way is not going to have a bit of impact on my shooting.

 

[2aBaC̶a̶]

Is that just an accel spreadsheet or some app?

 

[Dewey7271]

Dammit, I just settled on RL-26 for my 20 inch 280 Ackley Improved project.....

It works very well in that cartridge for me. Hunting rifle.
Around 60 gr with a 160.

 

[Holliday]

It works very well in that cartridge for me. Hunting rifle.
Around 60 gr with a 160.

If I can find any. What is your barrel length?

 

[Ol' RD]

Is that just an accel spreadsheet or some app?

It’s numbers, excel for a Mac.

 

[Dewey7271]

24”

 

[wapiti16b]

Temperature sensitivity and harmonics for repeatable accuracy determine my powder choice.