QuestionableMaynard8130 wrote on Jun 3^rd, 2015 at 8:07am:


Wouldn't there be two answers to that?

One for dual base powders and one for single base?   

The tests for resolution of that question might necessarily look like the Lee chart that lists BHN versus pressure required to achieve obturation.   

Anyway    I too have experienced 5744 and seen what you saw.   And almost gave away that first bottle after the first 5 shot string.

But then I copied down the chronograph readings.   It's just possible the answer to this conundrum MIGHT could be crafted ALMOST immediately, if not sooner.   Wait....  how can "sooner" come before "almost immediately"?    

Uhhhh....   What brand of coffee do you favor?   (please include your Pet Load information as to either weight or volume of grains... uh, grounds.... etc etc)

(I need a Smilie here that slaps itself)    (of course, others MIGHT suggest that I need a Smilie that is slapped......   oops


ANYWAY....   I would suggest that 5744 is a perfect example for anyone who would suggest that some powders give excellently consistent pressure/velocities even when not individually weighed.    It's a double base.   They're usually more consistent in ignition I believe.   So there appear to be powders that either won't vary the amount of unburned powder or somehow produce unvarying pressure/velocity if they do.      

I've been experimenting with 5744 in a 40-65 since the middle 90s.   I recently got a 40-70SS that kicked that same testing off again.   Outside of the usual things we quest after, it amused me to see HOW LOW CAN WE GO......   with 5744.   I figured to use the chrono to warn me that the load was getting too low.    Predicted first shot velocity was verified before shooting a 2nd.   Each shots velocity was noted for the same reason.  Total variance (or extreme variance) was used as well.   Temperature was considered up front (and back).   

That powder, so far, appears to me to be a powder that would answer your question as:   clean vs dirty doesn't matter.   

I would actually shy away from trying to get most powders to shoot dirtier than what I'd identified as normal for them.  And I think proving your question would require reloading in a way that would get the subject powder to be dirtier, as proving "really mattering" between two different powders seems to me to be impossible.   I'd suggest it being impossible for any of us to prove WHY two different powders (whether they're clean, dirty of whatever) differ in whatever is chosen to matter.    

(maybe I will try decaf first)

SR4759 will leave large unburned grains of powder at lower pressures. If you have as strong rifle bumping the pressure up a grain or two often gets rid of the unburned powder.

Then your bullets are not running over these grains when your fire a round.

Questions like this are what makes the endeavor to shoot well consistently so interesting. While having unburned powder in the barrel seems like both a waste and a troublesome possible source of bullet flight inconsistency, internal ballistics are sometimes obscure enough so that the results we get sometimes don't seem to make sense - things happen that shouldn't. Perhaps a particular combination of components and rifle provide just the right pressure rise and burn rate so that the previous unburned powder is puffed out of the barrel right before the bullet obdurates perfectly, then leaves the barrel consistently, dropping the pressure to leave the remaining grains to extinguish in the barrel, prompting us to mourn pennies lost from powder inefficiency even though the bullet flies true. Seeing data that prompts a "what the...?" is usually an opportunity to learn something significant. Looks right - does right/looks wrong - does wrong, well, that just makes sense. Looks right - does wrong/ looks wrong - does right, now that's interesting.

A number of very popular (but dirty) powders have been advertised to be reformulated to be cleaner.    

Anyone had experience with any of those, before and after?   Did it matter?   Well, matter to something more than cleaning the gun after shooting, that is.

Bullets shot through a fouled bore / unburnt powder in BPCR SillyWet competition probably isn't a real handicap as the targets leave plenty of room for error but doing the same in an ASSRA group match with no room for error it probably is. It all depends on how much one wants to get out of his rifle. To some good is good enough and to others like myself it isn't ever good enough so I try what ever it make take to make it better. The road to the best in accuracy is the elimination of variables. Does unburnt powder left in the bore really affect accuracy? I don't believe anyone can prove it one way or the other but it is easily eliminated by the right choice of primer and that variable will no longer exist and you are then on the right road to success and one won't have to wonder if that flyer in what started out to be an outstanding group might have been caused by that unburnt powder left in the bore.

JLouis

BPCR Silhouette Shooters  work to keep the barrel the same for each Shot! Either by Blowtubing after each Shot, or Wiping the bore after each Shot! I don't know any of them who let the fouling build up for a certain amount of shots before wiping...

Terry