Case fill and burn %

I'm kind of with post number 2

I've done with some good success compressed loads on pistol round that have been maybe 115%.

While tinkering with some 6mm loads for competition, I've compressed with no pressure signs or issues. It just shot like ****. I think beyond that for 110% fill of h1000 would NOT have been safe for pressures. Thinking back on it.

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

Just an FYI 100% case fill does not mean 100% of the space inside of the case has powder. 100% case fill means from the bottom of the case to the bottom of the bullet is full of powder. The bottom of the bullet(if protruding into the shoulder/case) will barely touch the powder in a 100% case fill load. The free space around and above the base of the bullet(boat tail, etc) is not counted towards case capacity. This is why you can be at 100% case capacity and still hear powder shaking inside. Also 100% burn rate is a must. Id rather take 80% case fill and 100% burn rate than a load with 99% fill and 90% burn rate. Because that 90% burn rate at 70 degrees will be a 94% burn rate in 90 degrees or a 86% burn rate in 20 degrees. Your velocity will be all over based on temperature alone. The softwares that we have available give us no reason to choose a load with less than a 100% burn. That being said, you can find you have a 100% burn rate powder in 60-100 degree temps that dip below 100% in 20-30 degree temps. When I am running softwares I make sure my powder is 100% burn in my temperatures I experience which is a 20-80 degree window.

I use QuickLoad to find fastest powder at 104% load density, giving me intended peak pressure (like 65Kpsi) while off the lands (OTL), and <8Kpsi muzzle pressure, from my barrel length and case capacity.
That's how I initially choose powder.

Load density does make a difference to ES and tune, especially with sloped shooting.
If you test it yourself, I have, i bet it will amaze you.

FEENIX said:

Per my previous response, I prefer >90%, so most strive towards a 100% fill ratio and sometimes beyond.

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I am also on the >90% fill process - I have a couple of rifles that are near 95% but rarely do I approach 100% fill. I find that in temperature variations - especially very hot weather, the 100% fills tend to show more pressure signs and greater variations in SDs.

This is all dependent on ladder testing and results - some rifles shoot better at 90% - some 94% etc....but I like to keep my cases as full as I possibly can.

Huntaddict said:

I am also on the >90% fill process - I have a couple of rifles that are near 95% but rarely do I approach 100% fill. I find that in temperature variations - especially very hot weather, the 100% fills tend to show more pressure signs and greater variations in SDs.

This is all dependent on ladder testing and results - some rifles shoot better at 90% - some 94% etc....but I like to keep my cases as full as I possibly can.

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Id make a hefty bet those 100% fills that are showing pressure signs are actually over pressure at those hotter temperatures but under at lower temps. PRS guys deal with this a lot because theyre always trying to squeeze out the highest velocity to get a little edge in the competition. Then they go compete in 100+ temps and they're blowing primers or have sticky bolts and its because they did all their testing in the lower temperatures where that specific load was under max and seemed fine. My 300prc hunting load max pressure is 80 degrees and I ended up shooting a boar in 84 degrees and had sticky bolt lift and cratered primer. My typical hunting temperature window is 20-60 degrees

coop2564 said:

Yes, its free and mostly based on Europe data and powders. If I plug in like 30-06 using reloader powder its real close. But off using many Hodgdon powders, some are close within 100fps and maybe 2k on pressure. But my 6.5 grendel is 18" gas. If you have any data for 85gr hammer hunter or 123gr eld on TAC. my 85gr is 2.1660col, the 123 2.245. case is 35.8 h2o.

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What does your MEASURED data say? Your actual in your rifle. BTW they are both modeling software, you need to calibrate.
I ahve used QL since windows 3.3? and GRT for over a year.

I prefer full to slightly compressed! I'm not terribly opposed to somewhat heavily compressed! memtb

drabdrew said:

Id make a hefty bet those 100% fills that are showing pressure signs are actually over pressure at those hotter temperatures but under at lower temps. PRS guys deal with this a lot because theyre always trying to squeeze out the highest velocity to get a little edge in the competition. Then they go compete in 100+ temps and they're blowing primers or have sticky bolts and its because they did all their testing in the lower temperatures where that specific load was under max and seemed fine. My 300prc hunting load max pressure is 80 degrees and I ended up shooting a boar in 84 degrees and had sticky bolt lift and cratered primer. My typical hunting temperature window is 20-60 degrees

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Probably some thing to that. I only run at the top of the ladder with hunting loads. I hunt anywhere from -20 to 120 so it's expected. i won't run it if i blow primers. sticky bolt at the top end is fine

Target and practice rifles i run where the rifle likes it to maintain accuracy at the node and bbl life

coop2564 said:

Yes, its free and mostly based on Europe data and powders. If I plug in like 30-06 using reloader powder its real close. But off using many Hodgdon powders, some are close within 100fps and maybe 2k on pressure. But my 6.5 grendel is 18" gas. If you have any data for 85gr hammer hunter or 123gr eld on TAC. my 85gr is 2.1660col, the 123 2.245. case is 35.8 h2o.

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So many powders are so much better than TAC.

drabdrew said:

Id make a hefty bet those 100% fills that are showing pressure signs are actually over pressure at those hotter temperatures but under at lower temps. PRS guys deal with this a lot because theyre always trying to squeeze out the highest velocity to get a little edge in the competition. Then they go compete in 100+ temps and they're blowing primers or have sticky bolts and its because they did all their testing in the lower temperatures where that specific load was under max and seemed fine. My 300prc hunting load max pressure is 80 degrees and I ended up shooting a boar in 84 degrees and had sticky bolt lift and cratered primer. My typical hunting temperature window is 20-60 degrees

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Huntaddict said:

Probably some thing to that. I only run at the top of the ladder with hunting loads. I hunt anywhere from -20 to 120 so it's expected. i won't run it if i blow primers. sticky bolt at the top end is fine

Target and practice rifles i run where the rifle likes it to maintain accuracy at the node and bbl life

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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

I like 90 to 100% case fill.
And 95 to 100% burn.
Some cases and bullet that's not possible or realistic.

coop2564 said:

Yes, its free and mostly based on Europe data and powders. If I plug in like 30-06 using reloader powder its real close. But off using many Hodgdon powders, some are close within 100fps and maybe 2k on pressure. But my 6.5 grendel is 18" gas. If you have any data for 85gr hammer hunter or 123gr eld on TAC. my 85gr is 2.1660col, the 123 2.245. case is 35.8 h2o.

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Coop, have you added in the gas port size and position for the grendel? Makes a difference. Have you calibrated the powder model? Measured everything?
With revolvers the cylinder gap also needs to be input.
European powder companies share their data making their powder models much more accurate.. American companies like hodgdon do not.
According to charlie at grt, you want the 95% burn line within the last 2" of barrel to be considered efficient.

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 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.