amount of powder burned in a given barrel

[Jac Spring]

I have seen several referrences to the amount of powder that will burn in a given barrel.

The thing that comes to mind when I see that is the fact that bp only burns about 50% of its weight right? The rest is smoke and soot after combustion.

So how does that effect the "total amount" of poweder burnt or utilized (probably a better term) in a load?

I mean if a 32", 54 caliber barrel only utilizes 75 grains of powder (per the formula) does that mean before combustion or during? The latter would indicate that the barrel would in fact be able to utilize 150 grains (pressure notwithstanding of course) before the ball exits...

Just wondering...

 

[Blizzard of '93]

Can't give you the formula, 'Paul V' will have to weigh in here, but after a certain amount of powder charge in a short barreled rifle according to projectile weight and grain size of powder there won't be much increase in velocity and a lot of unburnt powder out the muzzle, a heavy slug (minie ball) can be overcharged- i.e. 'dangerous pressure' so there is a limit to the powder charge for PRB and slugs which beyond that will net no returns. I think you should go over 100 grs. with caution.

 

[john12865]

I'm no expert on this.
I can tell you that the difference between a Max. load for a gun and the Max. effective load are two different animals.
While a barrel may be rated for 100 grs. The Max. effective load may be 75 grs.
Every gun has a sweet spot which will make it shot accurate.
So that sweet spot maybe 75 grs. for that given gun and caliber and any thing above that just causes a big boom,lots of smoke,excessively fouled barrel and a bruised shoulder.
There is no advantage to a max load in any gun, other then the above.
Max. load will not be the accurate load.
This is what confuses people. They wonder why they can't get any accuracy.
Every gun has it's sweet load and your not going to find it with out taking time to learn the gun.
The gun teaches you what it likes. You don't teach the gun.
Most Traditional muzzle loading guns are 100 yard guns. A man that really knows his gun might knock a deer down at 125 or 150 yrds. but he knows that gun really well from lots of practice.
It's not as simple as doing the math.
Two of the same guns will shoot different, These are the unknown variables. :grin:

 

[roundball]

"...There is no advantage to a max load in any gun..."

Well, unless you didn't mean what you typed, that's a pretty absolute statement there with which I'd like to respectfully disagree...:grin:...and I say that based upon the certainty that anyone accepts that the Thompson / Center Arms company knows what it's doing with respect to muzzleloaders, and that the blackpowder manual they publish containing load data charts can also be accepted as factual.

TC's load data charts show incremental steps up to & including their published max load for a given barrel / caliber / projectile;

And those max loads list higher velocities and energy levels than the preceeding incremental step before it in each respective caliber chart.

IMO, increased velocity and energy levels through each incremental step up to and including the max load can clearly be seen as advantages.

 

[Slamfire]

There is more to the accuracy equation than the amount or powder, even the efficiency of the burn. Barrel vibration is a big factor, as are how the projectile fits the bore. Your rifle will tell you what it likes best, and if accuracy is your prime objective you should use that load.
If there is some other criteria, such as energy. and accuracy is of lesser importance, then a balance must be struck.
If energy is the only criteria, then maximum loads are the way to go. BUT maximum in one rifle is not the same as maximum in another, or with a different projectile. That's what makes load development so interesting. :hmm: :thumbsup:

 

[paulvallandigham]

The formula for determining the maximum amount of powder that will burn in your barrel using a PRB is 11.5 grains per cubic inch of bore. or Pi R Squared) times 11.5 times the length of the barrel in inches. R equals the radius, which is 1/2 the diameter of the bore. Use the caliber designation of the rifle for the bore diameter, and divide by two. Then multiply that number by itself to square it, then times 3.1416, then times 11.5 then times the length of your barrel in inches. That last figure is the maximum amount of powder that can be burned in that barrel length for that caliber. The larger the diameter of the bore, and the longer the barrel, the more powder can be burned.

This formula does not mean you can stuff more powder in the barrel. It only means that relative to the weight of the round ball, the amount of powder that can be burned inside that length of barrel is the figure indicated by the formula. Everything else is burning in front of the muzzle and adding little to the velocity of the ball. It does, however, add to the recoil forces in the gun, some of which are dissipated by the weight of the gun, and the shape of the stock, and the rest hits you in the arm or shoulder.

 

[Jac Spring]

OK, nobody really answered my question directly though Paul, I think you are indicating that it is the loaded charge that is addressed by the formula. Futher, this is for prb's and not conicals.

So, you are saying that the maximum amount of powder that will actually burn in my 32" 54 cal barrel is just under 85 grains. Anything over that will not increase velocity - right?

Roundball's comment is pertinenent to conicals only then - right? Or does TC show velocity increases for prb's too?

Paul, do you have a formula for conicals? Would need to factor in bullet weight...

Do we have chronograph data to prove this out?

I'm just interested in understanding how this works.

I'm perfectly happy with the velocity of the ball with 85 grains or less for hunting should I choose that.

If I want more push on the game, I'll use my Renegade 50 with it's 1:48" twist and heavy bullets...

 

[Mad Monk]

I have seen comments on the Internet about how much powder you can burn in a given bore. Usually stated that beyond a point in charge size you are blowing unburnt powder out the muzzle after the ball or bullet leaves the muzzle.

Using 2F or 3F you would have to shoot some gonzo charges to see anything approaching that.

The bigger issue is the ability to convert gas pressures behind the projectile into increasing velocity in the ball or bullet. You reach a point in charge size where you simply cannot convert gas pressures to velocity with the same degree of efficiency (effectiveness) as with the smaller charges.

Big max charges do not always provide the required degree of accuracy to do any hunting at acceptable ranges.
The NMLRA used to tell you to work up in charge size from "1 grain per caliber" as a starting point. You will normally see groups tighten up. Then a point will be reached where the groups then begin to open up. Sometimes they open up dramatically.

Twist rates have an effect on this. Generally, slower twist rates require larger charges for the best accuracy if the shooter wants high velocities and tight groups.

 

[paulvallandigham]

NO, I did not say that putting more powder in the barrel than 85 grains won't increase velocity. All I said is that that is the maximum amount of powder your barrel will burn efficiently. When you put more powder in the barrel, it adds weight to the charge, with half the additional powder adding recoil forces to the back end of the gun. If you chronograph the loads as you increase the amount of powder over that given number, you will see that the increase in velocity for each increment of additional powder becomes less and less, when compared to that same increment in powder under that maximum amount. You are getting less and less for more and more, which means you are wasting your money for almost no gain.

This becomes even more painfully obvious when you move the chronograph out to 50 and then 100 yards and take your readings at the down range distances. You will quickly see all that extra velocity you saw at the readings taken in front of the muzzle ( muzzle velocity) disappear almost entirely at the longer range. This is the result of a basic law of physics, which says that whatever goes faster, slows faster. This is particularly true for Round Balls. Remember that your RB is going to drop down through the sound barrier at some point short of 100yards, unless you are shooting a very small caliber gun . Even those .36 and .40 caliber guns will see a RB drop down within 150 yards. The smaller diameter is good for a starting or muzzle velocity, but the weight of the RB is so light that the ball cannot sustain the velocity. You are far better off in choosing a .50 or .54 or .58 caliber rifle for hunting if you truly believe that the range you will have to shoot game at will be 100 yards or more. The heavy weight of those balls will penetrate thin skinned animals much better, with the RB from the larger two calibers capable of completely penetrating both sides of a deer standing broadside, even when they are traveling at under 1000 fps.

 

[roundball]

Roundball's comment is pertinenent to conicals only then - right? Or does TC show velocity increases for prb's too?

I was actually referring to patched round balls but TC's manual has load data charts for their maxi-hunters and maxi-balls too.

All of their incremental steps in all of their charts show velocity & energy increases right up to and including the max.

Their data is based upon their standard 28" x 1:48" barrels.

 

[Jac Spring]

Paul V: OK I understand what you're saying. When you stated that the formula gives the "amount of powder that your barrel will burn" it sounded absolute, which is why I was confused.

Thanks for the explanation.

Again, I don't feel a need to rack it up and am perfectly happy with the "milder" charges if they give me the accuracy I want.

After all, I have a perfectly good Ruger .338 Winchester sitting in my safe - if I want power, I'll bring that out

 

[lightsky]

I JUST MIGHT HAVE THIS WRONG,BUT I THINK YOU
WANT TO KNOW HOW MUCH POWDER WILL BURN IN A GIVEN BARREL LENGTH.
IT TAKES A 32"BARREL TO BURN 120 GRAINS OF POWDER.
IF IT'S WHAT LOAD YOU CAN USE IN A GIVEN CALIBER,THAT ALL DEPENDS ON HOW THE RIFLE IS BUILT AND THE MANUFACTURERS RECOMENDATIONS .

 

[Many Klatch]

The best way to find out is to shoot over snow. If there is unburned powder on the snow in front of you after a shot, then you are overcharged.

Many Klatch

 

[Jac Spring]

I JUST MIGHT HAVE THIS WRONG,BUT I THINK YOU
WANT TO KNOW HOW MUCH POWDER WILL BURN IN A GIVEN BARREL LENGTH.
IT TAKES A 32"BARREL TO BURN 120 GRAINS OF POWDER.
IF IT'S WHAT LOAD YOU CAN USE IN A GIVEN CALIBER,THAT ALL DEPENDS ON HOW THE RIFLE IS BUILT AND THE MANUFACTURERS RECOMENDATIONS .

What? Eh? I can't hear you! :rotf:

 

[roundball]

The best way to find out is to shoot over snow. If there is unburned powder on the snow in front of you after a shot, then you are overcharged.
Many Klatch

Many, I tend to think that might be an old wives tale...as you know there's usually about a 3 foot flame that expands into a large area outside the muzzle as the shot is taken...and as easy as it is for BP to ignite, I don't believe unburned kernels that might actually exit the muzzle in that blast could survive that muzzle blast of heat and flame.

I believe what falls to the ground is BP residue / fouling like what remains in the bore...just my .02 cents

 

[Slamfire]

I'm of the belief that not all of the charcoal burns regardless of the charge weight. It just doesn't all get impregnated with the saltpeter when mechanically :v mixed.

 

[roundball]

I'm of the belief that not all of the charcoal burns regardless of the charge weight. It just doesn't all get impregnated with the saltpeter when mechanically :v mixed.

Don't know, guess anything's possibile...wouldn't have anything to do with barrel length though...just wouldn't burn regardless, eh.

I had some bad cans of Elephant years ago that had visible sticks of wood in it...pure junk.

 

[Mad Monk]

Slamfire,

In every sample of BP I have looked at in my work every bit of charcoal is burned in the combustion of the powder. I have pulled bore fouling and looked at it very closely.

Because you often see black bp bore fouling does not mean that the color is the result of unburned charcoal. When the R.H. is below 30% you will see damp patches used for between shot cleaning turn white in a few short minutes. That same patch will then turn gray and then black as the humidity goes up.

 

[Mad Monk]

Also forgot to mention.

The idea that the charcoal is impregnated, or saturated, with saltpeter during the milling of the powder is utter nonsense. The idea goes back into the early 1800's but simply does not wash when you look at the particle size of the charcoal in the finished powder.

At one time I set up a little show and tell demonstration to show that the idea of the charcoal being porous is nonsense.

 

[wildeagle]

If charcoal is not porous , why is it used as a filtering agent or to absorb poisons ,ect.