Question on propellants; how is it that a 4.5 inch barrel in a handgun can be different in accuracy?

[Alaskan]

If the velocity is identical with any required powder charge and with identical weighed projectiles and identical barrel in the identical firearm... why wouldn't the accuracy be in the same baseline?

How are different powder brands affecting accuracy other than needing different amounts to make the same velocity?

Longer barrels in rifles having harmonic mysteries is not being questioned... but why if velocities leaving the muzzle are identical with different brands and burn/ignition rates should accuracy be different?

Only difference might be consistent velocities but getting back to identical velocity counted from a chronograph wouldn't it be expected these projectiles to have near identical results?

 

[BTSDOG]

The barrels might be the same length, but they are not identical in regards to rifling and rifling dimensions. Bullets also have their own set of nuances..Core differences and jacket irregularities for a couple. Powders will vary from lot to lot. Burn rates will vary and pressure build up will also be affected. There are a shit ton of things that will affect accuracy. The weather, temperature and humidity will also affect accuracy to a degree. What kind of accuracy are you trying to achieve ? Unless your shooting from a ransom rest, i dont think youll get too close to perfection. JMO

 

[Broc]

Dont go down the accuracy black hole, it will drive you crazy. Just shoot whatever your gun likes best.

 

[Road_Clam]

Cripes, here we go again ...... This will morph into 31+ pages of armchair ballistics arguing that will end up ultimately ragging on a the . 40 S&W. May as well have asked "what kind of oil in my car" ?

 

[Mesatchornug]

Is it identical firearms, or the same firearm? I.E., are you trading two or more S&W E-Series 1911s built the same way, or are all tests being done in the same pistol with the same barrel?

 

[weekendracer]

Is it identical firearms, or the same firearm? I.E., are you trading two or more S&W E-Series 1911s built the same way, or are all tests being done in the same pistol with the same barrel?

Before I say Mobil One, I need this answer.

 

[rep308]

harmonics.....

 

[hunt4riches]

99% of it is in your breathing, shoulders, arms, wrists and fingers. The power, bullet, barrel and underlying platform are the last 1%

 

[Alaskan]

The barrels might be the same length, but they are not identical in regards to rifling and rifling dimensions. Bullets also have their own set of nuances..Core differences and jacket irregularities for a couple. Powders will vary from lot to lot. Burn rates will vary and pressure build up will also be affected. There are a shit ton of things that will affect accuracy. The weather, temperature and humidity will also affect accuracy to a degree. What kind of accuracy are you trying to achieve ? Unless your shooting from a ransom rest, i dont think youll get too close to perfection. JMO

My question is about different powder brands when everything else is identical.

if I use different powders and can find safe quantities to get identical velocities will the accuracy be equal?

did'nt imagine it would be this tricky to communicate... if I find an optimum load can I get equal performance using other brands to get there?

same gun... same barrel.

 

[Alaskan]

Before I say Mobil One, I need this answer.

Same gun same barrel different powders launching same projectiles at same velocity.

 

[Alaskan]

99% of it is in your breathing, shoulders, arms, wrists and fingers. The power, bullet, barrel and underlying platform are the last 1%

I'm using a SA-35 - set trigger... tick... pressure and... surprise!

 

[Alaskan]

Cripes, here we go again ...... This will morph into 31+ pages of armchair ballistics arguing that will end up ultimately ragging on a the . 40 S&W. May as well have asked "what kind of oil in my car" ?

Sorry... just occurs to me - are all powders going to be equal if everything else is the same including... VELOCITY?

 

[Alaskan]

The barrels might be the same length, but they are not identical in regards to rifling and rifling dimensions. Bullets also have their own set of nuances..Core differences and jacket irregularities for a couple. Powders will vary from lot to lot. Burn rates will vary and pressure build up will also be affected. There are a shit ton of things that will affect accuracy. The weather, temperature and humidity will also affect accuracy to a degree. What kind of accuracy are you trying to achieve ? Unless your shooting from a ransom rest, i dont think youll get too close to perfection. JMO

Same SA-35 9 mm - my question is about the numerous powder selection in times when these brands are difficult to find as it has been in Alaska?

is AA#7 the same as Unique or Auto-Comp if a safe quantity can obtain an identical Velocity in the same 9mm firearm?

 

[whacko]

Same SA-35 9 mm - my question is about the numerous powder selection in times when these brands are difficult to find as it has been in Alaska?

is AA#7 the same as Unique or Auto-Comp if a safe quantity can obtain an identical Velocity in the same 9mm firearm?

No they are not the same even if they produce the same velocity. Powders burn at different rates....creating different pressure levels and pressure spikes.

 

[vicorjh]

if I use different powders and can find safe quantities to get identical velocities will the accuracy be equal?

If you really want to get into this, get Quickload.



It's pretty good as long as the powder data is in the database and the inputs are accurate. You'll have a really good handle on the various parameters after entering all of the data. For rifle, the predicted velocities have been surprisingly close. Been awhile, maybe +/- 25fps.

 

[Alaskan]

No they are not the same even if they produce the same velocity. Powders burn at different rates....creating different pressure levels and pressure spikes.

But if in both cases the projectiles leave the same barrel at identical velocity... isn't this then beyond burn rates?

 

[Mountain]

My question is about different powder brands when everything else is identical.

if I use different powders and can find safe quantities to get identical velocities will the accuracy be equal?

did'nt imagine it would be this tricky to communicate... if I find an optimum load can I get equal performance using other brands to get there?

same gun... same barrel.

4.5" barrel accuracy from a pistol is relative. That said, how does the powder get to that accuracy? Fast burn / hard impulse all at once? Steady acceleration while moving down the barrel? Is there excess powder flashing off after the bullet leaves the barrel? All could affect accuracy.

I'm more of a rifle guy but in general I find the powders that reach higher velocities at lower pressures to be more accurate for a given caliber.

 

[Alaskan]

4.5" barrel accuracy from a pistol is relative. That said, how does the powder get to that accuracy? Fast burn / hard impulse all at once? Steady acceleration while moving down the barrel? Is there excess powder flashing off after the bullet leaves the barrel? All could affect accuracy.

I'm more of a rifle guy but in general I find the powders that reach higher velocities at lower pressures to be more accurate for a given caliber.

Interesting... I hadn't thought of slower burning powder continuing to flame excessively beyond the muzzle - thank you!

 

[BTSDOG]

Get yourself some good reloading manuals, and a good chronograph. Oh, and do you have a lot of free time ? Let us know what you discover....

 

[Alaskan]

... an interesting question and with reloading components having been scarce the potential of comparative performance within a broad range of brands will equal velocities meet ~ equal results?

mountain man had a solid reply - slower burning propellants may cause projectile stability issues after the release from the muzzle.

apologize if this bored anyone... thought someone had already been there?

 

[AMV]

But if in both cases the projectiles leave the same barrel at identical velocity... isn't this then beyond burn rates?

What about the pressure it takes to expel the bullet from the case and engage the rifling, If this differs between powders, the bullet could enter the rifling differently (Similar to COL's effect on accuracy) and although the velocity is the same flight characteristics could differ. But now we are talking about bench rest type accuracy differences.

 

[pastera]

My question is about different powder brands when everything else is identical.

if I use different powders and can find safe quantities to get identical velocities will the accuracy be equal?

did'nt imagine it would be this tricky to communicate... if I find an optimum load can I get equal performance using other brands to get there?

same gun... same barrel.

I thought I answered this in another thread

The velocity is pretty much determined by the area under the pressure curve - but the shape of the curve will cause the barrel to be distorted slightly differently which will change POI.
Lots of other things change that make the recoil and therefore your ability to hold the same POI different.

But some powders just aren't suited to the cartridge so they will have inconsistent burns resulting in poor consistency
Putting your load into Gordon's Reloading tool shows burnout after the bullet exits and only ~78% of powder burning so you get s nice big flash
Using my preferred powder, Silhouette, gives similar velocity (1150 v 1180) but burns completely before exit (~4.1") so you get very consistent burns with little muzzle flash

Reloading is much more complicated than just hitting a velocity - you need to match bullet weight to powder speed with case volume/fill. You can't just swap out powders and change charge weight to achieve a given velocity. Everything is a trade off.

 

[StevieP]

What is the objective of this exercise? I consider a 9mm handgun a defensive use gun. "Minute of black bear" is accurate enough, no?

 

[DW357]

is AA#7 the same as Unique or Auto-Comp

Is this a serious question?

 

[Broc]

What is the objective of this exercise? I consider a 9mm handgun a defensive use gun. "Minute of black bear" is accurate enough, no?

Depends. Are you shooting minute of black bear at a self defense distance? (Meaning fairly close, 10-15 yards).

If you are, then you need glasses, or a new gun or to work on your shooting.

 

[Mountain]

... an interesting question and with reloading components having been scarce the potential of comparative performance within a broad range of brands will equal velocities meet ~ equal results?

mountain man had a solid reply - slower burning propellants may cause projectile stability issues after the release from the muzzle.

apologize if this bored anyone... thought someone had already been there?

@pastera already covered something I just thought of. Consistency. Some powders under a given condition just burn more consistently for whatever cartridge you are shooting. It's not so much about getting a certain velocity, it's all about getting a velocity that works for your application and getting as close to the same exact velocity every single time you pull the trigger. Also the powders might act differently under different temperature ranges. Some powders may not net the most consistent velocities at a given temperature but across a wide range of temperatures will on average be much more consistent than others. +1 for using a chronograph if you really want to dive into this rabbit hole.

Regarding consistency, when developing rifle match loads I am looking for velocities with single digit SD (standard deviation) and an ES (extreme spread) below 15 fps. It takes some work to do this, especially in a gas gun (AR15 etc.). The pistol match guys can comment on what makes sense for you.

 

[whacko]

But if in both cases the projectiles leave the same barrel at identical velocity... isn't this then beyond burn rates?

If it's not yhe burn rate of the different powders then what are you suggesting is the variable?

Fast powders create a pressure spike and accelerate the projo quickly and the powder burns off mostly before the projo exits the barrel.

Slow powders create less of a pressure spike and accelerate the projo slower and in many cases the powder isn't all burned before the projo leaves the barrel creating muzzle flash and unburned powder leaving the muzzle with the projo. In my research and opinion that can definitely effect accuracy. Also experience in my loading supports this. H110 in pistols for me anyway proves less accurate than unique.....even loading them to produce the same velocity.

 

[gerrycaruso]

Your theory is flawed. You're assuming that the interior of the barrel and the projectiles are identical. They are not. They are very similar but not exactly the same because of machining tolerances.

 

[Mesatchornug]

Your theory is flawed. You're assuming that the interior of the barrel and the projectiles are identical. They are not. They are very similar but not exactly the same because of machining tolerances.

He's using the same barrel. Differences from one projectile to the next have to be accepted.

@Alaskan - they keep telling you that the area under the curve is actually what matters. We use muzzle velocity as an abstraction because it's easy to measure, but it's an incomplete picture of what's going on. Depending how fast the powder burned, instantaneous change in acceleration could be positive, zero, or even negative at the time the projectile leaves the muzzle. This will affect your velocity immediately after it leaves. Heck, it can even affect how long it takes the projectile to get to the muzzle.

 

[pastera]

Your theory is flawed. You're assuming that the interior of the barrel and the projectiles are identical. They are not. They are very similar but not exactly the same because of machining tolerances.

He actually was asking about different powders loaded to the same velocity holding all other things constant (same gun, head stamp cases, primers, etc)

My answer was that different powders have different burn profiles and even with the same velocity (ares under the curve) the differently shaped curve will excite the dynamics of the gun differently causing a different POI.
And that is between powders that are well suited to the load. Start using powders at the margins of their performance and inconsistencies show up that make accuracy all but impossible.
My worst experience with this was with autocomp, xtreme plated bullets and Speer 38spl cases fired from a 357 chamber. Squib city but load in a 357 case with the same charge weight and it was a great target load.
Only real difference was tension - the thin walled cases didn't grab the bullet enough to get the powder burning before the bullet jumped (0.135" extra chamber length)