Case fill and burn %

Huntaddict said:

I don't live in a vacuum. I hunt and shoot in reality

I have done this for years and have no issues with my set up and my system.

Single digit SDs. Great Accuracy. Great results.

Didn't really need coaching. was more sharing my experience.

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Sir, we all made mistakes in life…….some of us even admit those mistakes and learn from them! Thankfully most of us choose not to repeat our mistakes by altering our procedures!

I've made many, thankfully I was blessed with the opportunity to correct them! In those rare occasions…..you may not get a second chance!

Continue on as you see fit! memtb

memtb said:

Sir, we all made mistakes in life…….some of us even admit those mistakes and learn from them! Thankfully most of us choose not to repeat our mistakes by altering our procedures!

I've made many, thankfully I was blessed with the opportunity to correct them! In those rare occasions…..you may not get a second chance!

Continue on as you see fit! memtb

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I hear you, made a few on the way myself - don't let me new ness here influence you...been doing this a long time.

Enjoy and Merry Xmas!

I pay absolutely no attention to case fill percentage, because it's a meaningless measurement outside of compressed loads. Using Lee's 1-Graon calc factor, I've significantly downloaded almost everything in the 30-06 case family, and my 264 WM.
My 204 is the daily shooting warhorse against vermin arrive the ranch. It's most accurate load is a fair amount below the Hodgy starting load. But the burning curve is stable.

If it shoots small and within a decent velocity range for that particular cartridge....I honestly could care less about case fill and burn percentage.

memtb said:

I see this mentioned quite regularly, and each and every time……I am left bewildered!


This is for a hunting rifle…….not intended for a hunting rifle. This will take two seasons…….summer then winter! Patience is a virtue !


Develop your load in the hottest ambient temperatures you're likely to ever encounter when hunting. Allow the rifle and test ammo to reach ambient……though not in direct sunlight. Work up to your maximum that gives the accuracy that you desire.


Then, once winter is set in, allow the rifle and ammo to once again reach ambient temperatures. Now shoot across your chrono to verify your velocity and it's accuracy. If the accuracy is acceptable……you simply adjust the scope for the velocity difference if any!

I'm pretty darn certain that this will alleviate high temperature, high pressure surprises!

Perhaps I'm just a simpleton……but this seems a very logical approach to preventing the high pressure situation that we see mentioned on this and other forums many times! memtb

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I used to think this method was acceptable, but then found that the loads I made up and shot good in the Summer didn't do good in Winter & vice versa. Precision wise.

So, I have winter & summer loads reaching the same velocities using different charge weights. Sometimes even different powders.

Mike D Texas said:

I do my best to strive for 100% (+) case fill and 100% burn inside the barrel.

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I am not sure if you saw this thread, but the video is fascinating: https://www.longrangehunting.com/threads/slow-motion-bullet-muzzle-exit.371730/

ARlife4me said:

the slower the powder and shorter the barrel= less burn/burn completion. for the slowest powders you need a longer barrel and/or smaller case capacity. slowest powders tend to perform better in longer barrels as velocity won't decrease as much as medium to medium slow does (again it depends on case capacity). take something that holds 80-100grs with 8133, rl50, h50, 24v41 and 20n29 and with a 30" barrel you still might not get 95% burn rate. i like at least 92% fill and have gone as much as 115%.

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Have played around with cartridges trying to get 100% fill when I have 100% burn. Started seating bullet deeper which of course changed starting psi and also time in the barrel. If a person has good brass and even better turns necks, bullet jump up to .250" on my bigger gun did not effect accuracy (.338 / .378 Weatherby). A guy in Montana set me on to that years ago. He was running .408 / bigger stuff. I believe this also was easier on the gun / throat.
I always try to get 100% burn % fill. Powder choices have huge effect.

Michael Lares said:

Have played around with cartridges trying to get 100% fill when I have 100% burn. Started seating bullet deeper which of course changed starting psi and also time in the barrel. If a person has good brass and even better turns necks, bullet jump up to .250" on my bigger gun did not effect accuracy (.338 / .378 Weatherby). A guy in Montana set me on to that years ago. He was running .408 / bigger stuff. I believe this also was easier on the gun / throat.
I always try to get 100% burn % fill. Powder choices have huge effect.

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getting the most efficiency sometimes doesn't mean 100% burn or best accuracy (wish it did). what i've noticed using ql is the lower the muzzle pressure the more efficient it is. the 408 and bigger stuff makes sense on a 1/4 jump when bullets are 2.5" long or longer.

Brathany said:

I used to think this method was acceptable, but then found that the loads I made up and shot good in the Summer didn't do good in Winter & vice versa. Precision wise.

So, I have winter & summer loads reaching the same velocities using different charge weights. Sometimes even different powders.

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Exactly……hence my reason for saying they must be tested for precision and velocity at expected hunting temperatures! memtb

memtb said:

Exactly……hence my reason for saying they must be tested for precision and velocity at expected hunting temperatures! memtb

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That's not what you said to what I responded to.

ARlife4me said:

getting the most efficiency sometimes doesn't mean 100% burn or best accuracy (wish it did). what i've noticed using ql is the lower the muzzle pressure the more efficient it is. the 408 and bigger stuff makes sense on a 1/4 jump when bullets are 2.5" long or longer.

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Works pretty good on 2" long bullets too.
Just for a grin, look at what more jump / deeper seating with 100% burn & 100% fill shows for muzzle pressure versus opposite , less jump etc. That's adjusting starting pressure to match jump of course. Pretty cool on QL to see this.

ARlife4me said:

what i've noticed using ql is the lower the muzzle pressure the more efficient it is.

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Unfortunately that's just not true, and another reason why people should stop pretending QL has very much utility.

Big picture to the point of this thread, everyone thinking slow powders are some drastically different thing. Needs to put their big girl panties on and pay attention, cause Uncle Satan's about to give the mouth-breathing section a case of the vapors.

IMR 4350 is generally a bit faster than H4350. Both of which are faster than RL-17, which is a fair amount faster than Superformance.
Right so, is this fallacy about burning speed was correct. Then when loaded in the same cartridge combo, we'll see that reflected in the rise times.
But the reality is that's not what we see at all, Traces below proving you don't see it.

Because it's Christmas, I'll throw in some 308 traces comparing RL-17 against 4895....

The Astute among the crowd will note the bullet weight difference in the 308, which should cause them to realize how variable burning rates actually are. Burning rate charts don't inform us of ANYTHING like, what most people wish they did. The primary mover is because they didn't even know how those charts are created. What most people actually want from a burning chart, is an energy release over time ratio. Which is something a burning rate chart simply cannot inform them of.

I've said this before, but think it needs repeating. If QL was even remotely as well informed as so many people believe, then why do they allow you to change start pressure? The start pressure in a firing event is atmospheric pressure. And moreover, why on earth would a program pretending to provide answers. Ask the user to guess at a NON EXISTENT pressure in order to give an "answer" to something else?!!?
The answer to that question, is because it doesn't have any idea how the powder is actually behaving. So it's attempting to guess how to fit an erroneous set of conditions, into a general time window.

Are you suggesting that being into or off the lands does not affect start pressure (and affecting peak pressure)?

I look for around 100-110% fill and the fastest powder I can use that shows definitive pressure signs at the max loads I have loaded for testing. Back that off just until the pressure signs are not present and that is my powder charge. I live in SE Texas so doing that at less than about 80 degrees is really hard to do. I don't see pressure signs at all at 100 degrees and it's difficult to hunt here below about 30 degrees using loads developed this way. I load 9/10 rifles with Hodgdon Extreme powders also, and that helps keep things predicable. If I can't get an ejector mark and a flat primer in my pressure test the powder is simply too slow for the cartridge in my book, so I move on. If it doesn't shoot well at the powder charge I have selected as appropriate I will change powder or bullet and try again. I don't try at all to improve on a mediocre load anymore, waste of time and money. If the load shoots pretty well I will move the bullet away from the lands in 3-4 large increments and test, the best seating depth there will get another round of testing with small increments shorter and longer, the best there gets loaded at the longest length that shoots well so as the throat burns the load stays in a seating depth that works well as long as possible.