IMR4064 Powder

[M14AMU]

Quite frequently I see IMR4064 powder being mentioned on this forum and I'd like to throw out a scenario for some feedback. Once upon a time at Camp Perry, Ohio at the National Matches I had the occasion to listen to a shooting clinic presentation being put on....think it was possibly by Middleton Tompkins...or maybe Creighton Audette and the subject of powder usage came up for long range shooting. One of the mentioned gentlemen had done extensive chronograph testing using 4064 with the Sierra 190 gr. HPBT bullet which was the most employed projectile during this particular era in the NRA Match Rifle category. Now...knowing both of the above gentlemen and their history of being in the shooting game I know beyond the shadow of a doubt that whichever gentleman it was.....this testing was not taken lightly or in a haphazard manner. The statement that stuck with me of this entire presentation concerning 4064 powder was that it showed extreme spreads of up to 49 fps. I thought that was rather odd at the time....and I still do! I shot some good scores using this powder and I often wondered how accuracy could be maintained with that wide extreme spread? We all know that a low SD is what we all look for in considering what would be a top powder for good accuracy but for some reason I can't get into my head how a wide extreme spread could jive with a low SD!

 

[RegionRat]

Do you know for sure the speaker was discussing ES or are you sure it was really SD?

In general, if you shot enough samples, something on the order of 15 to 30 shots for example, your ES would start to look like roughly 6 x SD. This assumption usually plays out since the performance tends to follow a "normal" distribution, aka Gaussian Distribution. I could see a short term sample giving an ES on that order, which may eventually open up a little with more samples.

However, maybe I don't follow your question, but an estimated SD from an ES on the order of 49, would be 8.17 fps. Question would be why you think that was out of family? It sounds about right for MR or Long Range use, no?

 

[M14AMU]

IIRC the presentation was about both; ES and SD and accuracy in general. I'm not educated in statistics to thoroughly understand the probability of the 49 fps shot evolving but I do understand that I'd much rather work with a powder that would consistently possibly deliver an ES of nothing over....let's say 15 fps instead of 49 fps!

Thanks for your reply!

 

[RegionRat]

It may be that for small samples, an ES that small (15) is just a matter of random chance. Single digit SD would have to be very small, say on the order of 2.5 to be real. I have seen SD that small, but they don't seem to hold for long in the real world.

A SD on the order of 9 fps would still be single digit and would give an ES of roughly 54 fps, which would still give a tight vertical.

 

[boltgunluvr]

Top notch guys. Bottom line....IMR 4064 .......was AND is a great propellant.

 

[rminut]

http://riflemansjournal.blogspot.com/2010/07/statistics-for-rifle-shooters.html

the link is pretty much everything you need for the statistical breakdown in shooting. His testing used Varget and had almost identical ES?? sounds like there is more to the numbers than just the powder.