Diminishing Returns?

[nkbj]

It doesn't. There's finding the very most accurate load and there's finding the most accurate loading method at a given velocity. Two different animals all together. And the second one takes knowledge gained through experience with the piece.

 

[George]

Yeah, but what they are discussing is the most efficient load. For me and the way I shoot/hunt, that just doesn't compute.

Spence

 

[galamb]

I think we all have certain things that we (overdo), exceed not only the minimum threshold but exceed it significantly.

I can pull my 14', 300 lbs aluminum boat with the wife's 4 cylinder car. Has more than enough brakes/guts to get it going and stop it, plus more than enough to pull it out, on the trailer, on a well inclined launch - but I still hook it up to my 1/2 ton - I'm overdoing it - burning more gas, but "don't care".

Now, if I hooked it on a 1 ton diesel dually I would really be overdoing it - will it work, sure, but do I need that much - no, not under any conditions.

Shooting a max load is like that. If 60 grains will do the job, that's taking the car. Maybe 80 grains is the 1/2 ton and if you max out at 110/120, that the dually.

Just depends how you want to spend your money. And when shooting Bambi, he is just as dead with 60 grains as 120 and he didn't care whether it took .118 seconds to hit him or .093 (and that's the difference in my 45 @ 50 yards between a 70 and 110 grain load)

 

[teepee]

In your calculation what does the 11.5 represent?

So, if I have a .62 caliber barrel that is 53 inches long. The radius is .31, squared is .0961. So PI 3.1416 x .0961 x 53 = 16.00 or 16 cubic inches of bore volume. Multiply 16 x 11.5 (what is this number) = 184 grains?? is approximately how much powder that barrel can burn efficiently.

If correct, I wouldn't want to shoot that load!

 

[George]

Most hunters on these forums seem to build their whole strategy around the 50-yard shot. They sight in for it, think of the power needed in terms of it, even refuse to take longer shots than that. That's a good plan, but it's not mine. I plan for the 100 yard shot, calculate my trajectory to handle that, build my charge for adequate velocity and energy at that range. Anything shorter then seems much more comfortable. I've never taken a shot quite that long at a deer, but if the right circumstances come up I can, I'm prepared, and I will.

As Clint has been known to say, a man's got to know his limitations. :haha: The man won't if he hasn't tried it on for size and planned ahead.

But we were talking about efficiency. I'm agin it. :grin:

Spence

 

[galamb]

The 11.5 is the number of grains of powder that can be "consumed", efficiently burned, per cubic inch of bore.

So yes, your 62 cal would be .31 x .31 = .0961 x 3.1416 = .3019 x 53 = 16 x 11.5 = 184 grains

Now that doesn't mean you want to pull the trigger on 184 grains BUT if you did your barrel would be "capable" of wringing every bit of power out of that load.

A shorter barrel with THE SAME LOAD (or a smaller caliber) would blow a portion (maybe a lot) of the powder out of the barrel before it could transfer it's "power" to the ball/projectile.

In a large bore this number has less meaning than in a smaller bore if you are looking to maximize powder use.

So while you will still get more velocity with a charge greater than can be consumed, more of it is "wasted".

 

[azmntman]

As would be the ligaments and nerves in your shoulder! :shocked2:

 

[larry wv]

Dead is dead and out of the water is out. But what if it started sleeting and wind blowing and a Tornado started coming over the hill. Would you want your wife's car or the dually truck? Just like hunting s--t happens. Best to have a bit of over kill.(pun not intended)? :v Larry

 

[galamb]

That's exactly why there is no "one size fit's all" answer.

I hunt from my bow stand in dense hardwoods.

My shooting lanes are only cut out to 35 yards. There probably isn't a clear shot in any direction, including straight up, even 50 yards out.

Therefore "I" have zero need of sighting beyond 50 yards and can "lethally" reach any game that would come within shooting range with a minimal powder charge.

(and if there was a chance of sleet I wouldn't have the boat out - don't live in a tornado area - never even seen one other than on the news and live less than 2 miles from the boat launch)

So it really is about how (you) use your rifle (or boat) as the case may be.

And not knocking the OP but when a newcomer throws out a question about max loads, max velocity etc, that just screams "I want this muzzle loader to shoot like my 7 mm Rem Mag - how do I do it?"

Maybe if they are hunting across open fields they should sight for 100 yards and work up the strongest load that will group within 2 or 3" at that yardage, but if they are still hunting or stand hunting in dense woods max velocity/max powder will be of little benefit (unless they already feel "handicapped" and need to wrap up in it like a safety blanket).

Better to live within the limitations of the weapon instead of stretching it out to it's max range - at least until you have fired a few hundred rounds under different conditions so that you know how it's going to react and learn if you are "capable".

If it's going to come out of the locker a couple days before the blackpowder season - get a couple of range shots to make sure it fires and then off into the woods for the "special season", perhaps it should be relegated to 50 yards....

 

[George]

The 11.5 is the number of grains of powder that can be "consumed", efficiently burned, per cubic inch of bore.

And the science behind this is...?

Spence

 

[hanshi]

In my .45 I get a bit under 1800fps with 70 grains of Goex, a .017" patch in the 36" barrel. Have yet to chronograph it with my usual 70 grains of JBP and a .024" patch; but going by what I've experienced with JBP in other rifles, I'd expect to get something over 1800fps.

 

[galamb]

And the science behind this is...?

Spence

There is no hard science, and this has been debated on this forum numerous times.

You either believe it is valid based on the empirical evidence that was provided with the many original posts or you think it's "hoooey".

Many would say that empirical evidence itself is non-sense unless such evidence can be quantified in double blind tests which show similar results.

To that I typically respond -

I spent a number of years in the military and on many occasions I exited an aircraft with a "backpack" strapped on that contained a parachute.

Despite the fact that there has never been a double blind study to show that you are less likely to survive the fall from the aircraft "without a parachute" - no "repeatable testing" has ever been conducted to quantify the "empirical data", I was not swayed to attempt the jump "without" a backpack.

Likewise, if you shoot with a charge greater than what the (so named) Davenport formula considers "optimal" you begin to see "chartable and measurable" "diminishing" returns.

For me that tends to indicate some validity to the formula. And until such time as someone else invests the time and money to do extensive testing with various powders, in double blind lab tests to show otherwise I will use this as "MY" benchmark.

The formula tells me that the most efficient load for my 36"/45 cal is 68 grains and my own chrono work tells me that after 80 grains (of 3F which consumes itself quicker than 2f) things start dropping off rather quickly.

For me that's close enough to believing a parachute is packed in that pack on my back..

 

[Claude Mathis]

Once I develop the most accurate load for as given gun - anything else; thinner patch, thicker patch, more powder, less powder - all produce diminishing returns. :wink:

 

[galamb]

Claude raises a good point.

My question to that would be, what is your charge with that "specific" rifle and how close is it to the "formula"?

And is "most accurate" load actually the "most accurate".

What I mean there is 1) is it the load that gives you the most consistent velocity, AND 2) the absolute tightest group.

Continuing to add powder may still give you an "accurate" group (but that is a "subjective" measurement - so perhaps a question better answered by target shooters who shoot for points and not hunters who may have an "acceptable accuracy" of say sub-2" at a given distance (80 or 100 grains may do that for you but at 75 grains the group may be sub .5" (as an example).

One final note then I will shut up for a bit.

Rice has a test chart that some are aware of posted up on their site where they started cutting down a barrel 2" at a time.

Anyhow, the barrel length that chrono'd the "lowest extreme velocity spread" (so most consistent velocity of all barrel lengths with a given patch/ball/load) was the 38" barrel.

The test was done with 80 grains of 2F, .490 ball and .015 pillow tick/bore butter - the barrel length was the only thing that changed 44" down to 30" in 2" increments.

The "variance" on the 38" barrel was 5 fps (chrono measured at 15' from the muzzle) - the most "consistent" of all lengths tested.

The "Davenport formula" for that 38" 50 cal barrel would say -

.25 x .25 = .0625 x 3.1416 = .19635 x 38 = 7.4613 x 11.5 = 85.8 grains

But of course, once again, that's just "empirical", but something to consider...

 

[Billnpatti]

The formula that I gave is called the Davenport Formula. It was developed by a man named
Davenport. The 11.5 is a constant that he developed. You can probably get more information by doing an online search for "Davenport Formula".

 

[azmntman]

THAT'S WHAT I SAID! :blah:

 

[George]

You either believe it is valid based on the empirical evidence that was provided with the many original posts or you think it's "hoooey".

Hoooey, pseudosccience, faith... whatever it's called, it's all armchair theorizing to my mind, and I'm sorry to see it continue to be passed along to the newbies as valid.

Now, if you had said every cubic inch of barrel could burn 11.4 grains, that would put a totally different light on it.

Geronimooooo!! :haha:

Spence

 

[galamb]

Spence, you and others obviously spend a lot of time working up your load to shoot in the circumstances you want to use your rifle.

I find value in formulas such as this (and the one for twist rate etc) for a either a new shooter or a new rifle.

It gives you a starting point to do your fine tuning/application driven "work ups".

And I believe actually it was 11.476/inch - just rounded up for those who still do their math "longhand" :rotf:

 

[ohio ramrod]

While there is definitely a point where the increase in velocity starts to drop off, the breech pressure continues to rise and at a certain point really starts to climb rapidly. Therefore for simple safety you should limit the amount you increase your powder charge. Far more important than maximum velocity is minimum group size. :hmm: :hmm:

 

[azmntman]

Far more important than maximum velocity is minimum group size.

:thumbsup: