223 velocity weirdness

[Ned Ludd]

...I thought that Benchmark was one of those "extreme" powders that wasn't supposed to be affected by temperature?????

"Extreme" powder is a marketing tool employed (quite effectively, I might add) to benefit sales. No powder on the planet is completely unaffected by temperature; some are merely less sensitive than others.

 

[savagedasher]

With H4350 I have ES change of 3 from 45 to 98 degrees . I would say that is insetive
Larry

 

[Ned Ludd]

With H4350 I have ES change of 3 from 45 to 98 degrees . I would say that is insetive
Larry

Insensitive, but not zero, exactly as I stated above. Also, your results are probably not representative of different "Extreme" powders. H4350 may be the least temperature-sensitive member of the entire "Extreme" powder family, according to Hodgdon's test data. I have been recording values in the neighborhood of 10-12 fps difference between ~60 degrees and ~90 degrees ambient temperature with H4895, not taking the SD values into account. The specific cartridge, case volume, bullet weight, and barrel length are all factors that likely influence temperature-sensitivity to some extent, because they all influence combustion.

 

[savagedasher]

Insensitive, but not zero, exactly as I stated above. Also, your results are probably not representative of different "Extreme" powders. H4350 may be the least temperature-sensitive member of the entire "Extreme" powder family, according to Hodgdon's test data. I have been recording values in the neighborhood of 10-12 fps difference between ~60 degrees and ~90 degrees ambient temperature with H4895, not taking the SD values into account. The specific cartridge, case volume, bullet weight, and barrel length are all factors that likely influence temperature-sensitivity to some extent, because they all influence combustion.

The small sample of 6000 round I didn't find that much . Larry

 

[msinc]

Insensitive, but not zero, exactly as I stated above. Also, your results are probably not representative of different "Extreme" powders. H4350 may be the least temperature-sensitive member of the entire "Extreme" powder family, according to Hodgdon's test data. I have been recording values in the neighborhood of 10-12 fps difference between ~60 degrees and ~90 degrees ambient temperature with H4895, not taking the SD values into account. The specific cartridge, case volume, bullet weight, and barrel length are all factors that likely influence temperature-sensitivity to some extent, because they all influence combustion.

Would it be fair and accurate to say that barrel length {longer making it worse or affecting it more} has the most effect out of all of the above mentioned factors????
I get what you are saying about zero or no temperature effect...that is not possible, I agree. I have seen pretty consistent results with the new IMR stuff. Especially IMR4166...not a bad 223 powder at all.

 

[Ned Ludd]

Barrel length, case volume, etc., likely influence temperature-sensitivity indirectly in that a powder can exhibit varying burn characteristics in different cartridges in which it is used because of these factors. In other words, they are all considerations that need to be taken into account when developing a load for a given cartridge. Some cartridges seem to produce inherently lower ES than others, likely due to better load optimization that is possible due to their shape, volume, etc. For example, it is very difficult to routinely get the ES below about 15-20 fps in a .223 with 90 gr bullets. This likely has to do in part with the small case volume. My point is simply that anything that influences combustion, and therefore optimization of a particular load in a given rifle, may well affect how that load behaves across a range of external temperatures. These effects may not be large as compared to the innate burn characteristics of the powder itself, but they are there nonetheless. Ultimately, they can all add up.