H4350 Temperature what ?

[David Milisock]

The set back pressure problem in my experisnce works as discussed in this post for rifles. Setting back the projectile reduces the leading edge of the pressure curve.

The math on this, (all other things being equal) as far as I know it is controlled by the expansion ratio. Case volume + bore/freebore volume divided by case volume.

1. In micro seconds the firing pin strikes, the primer backs out of the case, pressure builds, the projectile launches from the case and lodges itself in the bore.

2. At this point going forward the exact same volumes and parameters are applied to the two scenarios. A properly seated projectile and a projectile seated more deeply into the case.

The difference introduced by seating the projectile deeper in the case reduces the case volume and increases the bore/freebore volume.

So the actions that take place from ignition to the bullet lodging into the bore are only different in reaction because the initial area from the front edge of the projectile to the bore is larger.

This while not necessarily reducing peak pressure, must produce a slightly less vertical leading edge to the pressure curve.

An overcharged case depending on how highly over charged it is will still produce an over charged peak pressure. The increased free bore may be enough to circumvent this over charge peak pressure if it is a very slightly over charged load.

3. Going forward from paragraph 1, with the lodged projectile in the bore the powder continues to burn which causes the pressure to build, reseating the primer, expanding the brass of the cartridge sealing the rear of the chamber and allowing the pressure curve to build to peak as the projectile travels the distance of the bore and then the pressure recedes.

 

[Hohn]

For each i degree increase in temperature H4350 gains 0.29 FPS in velocity. Shouldn't make much difference.

Without putting too fine a point on it:

Baloney. Without knowing charge weight and barrel length you have no idea how temperature sensitive it is.

Please avoid sharing such misinformation.

 

[Nick Caprinolo]

Without putting too fine a point on it:

Baloney. Without knowing charge weight and barrel length you have no idea how temperature sensitive it is.

Please avoid sharing such misinformation.

Kind of an ignorant thing to say, since you don't know the source of my information. I find your attack to be offensive but I will excuse you this one time. There is no place for that kind of statement on this forum. The majority of us are gentlemen.

These published charts are based upon a 26 inch barrel. that is the norm for all manufactures. However the change in this case is so subtle, only 0.19 FPS, the difference in temperature is minuscule, and should have little effect. With a 20 degree change, that would only be 3.8 FPS which is why I posted it. All powder makers run these tests and there are published reports out there. Use Google and do some homework.

 

[Hohn]

Kind of an ignorant thing to say, since you don't know the source of my information. I find your attack to be offensive but I will excuse you this one time. There is no place for that kind of statement on this forum. The majority of us are gentlemen.

These published charts are based upon a 26 inch barrel. that is the norm for all manufactures. However the change in this case is so subtle, only 0.19 FPS, the difference in temperature is minuscule, and should have little effect. With a 20 degree change, that would only be 3.8 FPS which is why I posted it. All powder makers run these tests and there are published reports out there. Use Google and do some homework.

I apologize for the terse tone, I rarely feel it is warranted. I felt this was egregious enough to warrant direct rebuttal. Why? Because without providing any context to the poster, you pull a number from a report without supplying the context needed to know whether it applies to the situation at hand. NOW you say it is a 26” barrel; you did not before. And you still have not accounted for charge weight. Never mind that different cartridges and bullet weights will give vastly different results at identical charge weights.

The statement you made is only true for one set of boundary conditions which you did not supply. That suggests it is true in all conditions, which you do know or ought to know to be inaccurate.

A better approach would be just linking to the published report and let the viewer decide. Or stick to a generalization that H4350 is temperature stable.

 

[Nick Caprinolo]

You know, you are right and I am wrong.

You can't apologize for something and then say you were warranted.

I have done an extensive search and nowhere can I find a more definitive description on the basis for this data. Since there is no mention as to the powder load itself, It is my opinion and only my opinion, that powder load makes no difference , since each kernel is affected individually to the same degree. Therefor powder weight is irrelevant.

 

[Ironworker]

Shooters I'm the OP . 6mm Creedmoor 115 DTACs seated to I think within .020 to the lands 26"Bartlein bbl 40.0 grs H4350 ADG brass . Rem 9 1/2 LRP

 

[ormandj]

You know, you are right and I am wrong.

You can't apologize for something and then say you were warranted.

I have done an extensive search and nowhere can I find a more definitive description on the basis for this data. Since there is no mention as to the powder load itself, It is my opinion and only my opinion, that powder load makes no difference , since each kernel is affected individually to the same degree. Therefor powder weight is irrelevant.


View attachment 1193517

That is not how this works. Pressure changes the burn, as does the temperature being applied, burn rate is not a linear equation. There is no X FPS per Y degree simple variable substitution algebra. Any graphic or chart claiming otherwise either has a massive footnote describing conditions and notation that it is an average, or is misleading/wrong. You can say from 80-90F in 6mm PPC with an 90gr projectile of a certain type in a certain barrel, you’ll see, on average, a gain of 0.24fps per degree. It will probably be close for most barrels of the same general construction, with those specific conditions.

These charts are primarily useful on rough ranking of a powder’s sensitivity relative to others, but you need to test under your specific conditions to develop your own rule of thumb to apply. Linear application will only work on low sensitivity powders, and only then because while not linear, the variance is small enough that for most reasonable temperature swings the delta is low enough the average is close enough to barely matter on target.

 

[Nick Caprinolo]

That is not how this works. Pressure changes the burn, as does the temperature being applied, burn rate is not a linear equation. There is no X FPS per Y degree simple variable substitution algebra. Any graphic or chart claiming otherwise either has a massive footnote describing conditions and notation that it is an average, or is misleading/wrong. You can say from 80-90F in 6mm PPC with an 90gr projectile of a certain type in a certain barrel, you’ll see, on average, a gain of 0.24fps per degree. It will probably be close for most barrels of the same general construction, with those specific conditions.

These charts are primarily useful on rough ranking of a powder’s sensitivity relative to others, but you need to test under your specific conditions to develop your own rule of thumb to apply. Linear application will only work on low sensitivity powders, and only then because while not linear, the variance is small enough that for most reasonable temperature swings the delta is low enough the average is close enough to barely matter on target.

Giving further thought to this, I think you are spot on. The chart was most likely designed to show the degree of change of in each brand. This give you the ability to choose powders that have the least amount of change as temperature changes but not the actual increase, of FPS for a given charge.

Thanks for clearing this up for an old man.

 

[redrockranger]

The easiest way to deal with 1 gr. in a charge is to use a pair of tweezers and carefully drop in the pan of your beam scale.

 

[ormandj]

Giving further thought to this, I think you are spot on. The chart was most likely designed to show the degree of change of in each brand. This give you the ability to choose powders that have the least amount of change as temperature changes but not the actual increase, of FPS for a given charge.

Thanks for clearing this up for an old man.

That’s exactly what they are good for. The problem with all of the charts I’ve seen is they were crowd sourced and not measured all at the same time with the same temperature ranges. That’s why I say they are a good rough indicator, so you can generally be reasonably confident that the best 1/4 are relatively insensitive and the worst 1/4 are fairly sensitive. Beyond that, you test yourself. Glad I could help, I fell into this trap years ago myself, and learned from experience - I was hoping to save you a little $$ and time doing the same!

 

[David Milisock]

I'm not sure of any value in charts, for me the only issues are knowing the pressures are safe and knowing the velocities.

I simply work my loads when its warm and test them by exposing them to to direct sunlight. I measure the temp of the cases and fire a few every 5 minutes checking velocity and looking for signs of pressure. I do this for 2 hours if I continue to get safe results. If I'm going somewhere really hot I use lamps to warn the cartridges.

I use the reverse if I'm going to cold areas.

 

[Straightshooter1]

These charts are primarily useful on rough ranking of a powder’s sensitivity relative to others, but you need to test under your specific conditions to develop your own rule of thumb to apply.

IMHO, that's right on. And that's how I use these charts when considering which power I might want to use for a particular application. The same goes for the default burn rate used in apps like QuickLoad. When using QuickLoad, one will need to adjust the powder burn rate for a load based on chrono data to better representation of the accurate burn rate that might be used in subsequent loads with that same lot of powder.

 

[hottotrot]

You know, you are right and I am wrong.

You can't apologize for something and then say you were warranted.

I have done an extensive search and nowhere can I find a more definitive description on the basis for this data. Since there is no mention as to the powder load itself, It is my opinion and only my opinion, that powder load makes no difference , since each kernel is affected individually to the same degree. Therefor powder weight is irrelevant.


View attachment 1193517

This is awesome. I hadn't seen this chart. Every time I work up a load, I test the velocity of a single batch of ammo in the coolest and hottest conditions I can find in the season. Usually I fire 10rds over my Magnetospeed at ~7:30a.m. and then 10rds at the hottest part of a hot day of the week.
I've tested several lots each of H4350 and IMR4064 extensively in several chamberings, and have found almost exactly these numbers for H4530 and IMR4064.
H4350 is .3 for me, and 4064 is .6. Those numbers have been reliable enough that when I load for a new cartridge/barrel, until I get the chance to confirm exact numbers I just plug in these. So far, my calculator's never been off by more than single digit FPS with these inputs.

Reloder 15 has been .6 for me, but I've only used one lot and one chambering.
My one lot of Shooters World Precision in one cartridge showed no statistical difference from 70*-90*; tested that one twice to be sure.

 

[mauser284]

HaHa......I have some compressed loads in 300WM in IMR4350 that I developed in the Winter that I would be hesitant to shoot on a 91F or hotter day. It was about -8F to about -20F when I developed them. LOL So I can understand hesitation. Sometimes cation is warranted when you are at the limit! I jokingly consider them Elphant stoppers! LOL