I'm sure somewhere, somebody has discussed this but I've been unable to find it primarily due to the fact that I'm not sure what somebody would call it.  I'm interested if anyone has come up with a list of incompatible powders, and if not that, if at least somebody could explain to me which types of powders do not play well with each other.  I'm referring to when you have shot several rounds in a barrel with powder #1, and then proceed to shoot in the same barrel several rounds loaded with powder #2 and you do NOT have the opportunity or ability to clean the barrel/bolt between shooting.  I've witnessed several powders that do not interact at all, some that interact a little, and some that seemingly had bad interactions as they threw several flyers in the following group until it settled down after 3-4 shots.

With .223, shooting 4064 after 4895 I saw minor problems.
With 300BLK shooting 300MP after Remington Subsonics in 300BLK saw major problems
again with 300BLK, I4227 and then A5744 saw enormous amount of flyers for nearly 5 rounds.

Ones that haven't been a problem (for me at least):
N140 following H335
I4064 following Varget

Your POWDER should not be the issue. The charge or bullet could be. Your powder should be almost completely consumed in the firing, the only possible answers I see for your issue is that either their is unburnt powder left after a round is fired, or your load is causing an issue with the bullet's contact with the rifling, possibly excessive leading or jacket fouling?

Sierra touches on this issue in their manual #5 .

They may even have some info on their on-line exterior ballistics web site.

I can't imagine the problem is powder interaction.  If it was the powders interacting the first round with new powder would shoot fine, then both powder residues would mix and throw your next few shots....if that's even possible.

Dano, Thanks for your detailed overview.  While I'm familar with what you are talking about, its always good to hear somebody else's explanation of barrel harmonics.  And while I agree with most of what you state, I disagree with your assessment that it is causing my issues.  First, let me say that I'm not having any "issues".  I was just trying to gather information on what I thought was a well known and understood cause/effect relationship.

What I'm referring to about powder interaction is a documented phenomenon that many have seen, and some have written about.  I don't want to argue the merits of whether or not it exists, that doesn't interest me at all because I don't care much whether you believe it is real or not, that's your perogative.    I will only say that whether my situation is unique or not, I have no idea, but I just went into my shooting log table for the past 10 years and searched for how many instances I had where I switched powders during a shooting session, whether practice or not, in all of the calibers I shoot, without cleaning between the powder change, and it was over 3500 times.  So I personally have a lot of experience with this, and the data I've run myself on my own shooting shows there is absolutely a repeatable effect certain powders have when being shot after other powders that cannot be explained by anything other than that.  For instance, if you shoot a 20 round group, the first several shots will be erratic (and usually noticeable on the chrono as well), and they stabilize after the first 2-6, producing a very tight group (if the load is good).  No explanation of barrel harmonics or heat would explain this if you are managing to shoot at a defined interval when the barrel temp is not coming into effect.  Regardless, like i said, I'm not interested in arguing about this.  I merely wanted to see if anyone else who knows about this had bothered to document conflicting powders because I'm about to go through the trouble of doing it, and wanted to not duplicate efforts, or hopefully be able to skip doing it if it has already been done.  I've just not been able to find it anywhere, and for me the issue continues to pop up from time to time.

And for you non-believers, you should talk to Sierra and debate with them the merits of this phenomenon, as it is mentioned in their reloading manuals, and it is also talked about in a little more detail on their exteriorballistics page.  Its about 2/3 of the way down, paragraphs 4 & 5 in the section called Powder Selection.  Unfortunately, they didn't bother to put any anchors in the page so I couldn't link to it directly, but its easy enough to find by searching the page for powder selection then reading the last 2 paragraphs of that section:  http://www.exteriorballistics.com/reloadbasics/gasgunreload.cfm

If anyone does come along that knows about this issue and wants to share notes about specific powders, or can educate me on why certain powder types are more likely to induce this effect than others, I'd be most appreciative.

cheers.

Zpat:

You are bringing up what some call powder compatibility.

It is the residue from the first powder reacting with the second.......

It doesn't effect most shooters as it is a LR thing............

John Feamster in "Black Magic"  (pge 177-179) and Glen Zediker in "Handloading for Competition" (pge 389-391) both discuss it.  Usually when a switch from ball to extruded but others.  

I have a internet list I copied from there but I'm not sure if I can find it.............    

Here you go...................  

While my answer may not be exactly what you are talking about.. you did ask about cleaning the "Bore" ... so here goes... Some Match shooters say they have seen some problems when not cleaning the bores when switching between Ball and Stick powders or one brand v. another etc. , there is a list somewhere on my computer that shows what I'm writing about, any how I think thats how some of these gunny tidbits come about.

Here is the list of powders and their compatibility....

(Quote)..."Anyway, here is the compatibility list I compiled a few years ago. It is in no way scientific and compiled nearly 100% by hearsay."


Powder Compatibilities

Short Range Long Range OK?
2015 H4350 No
4895 N540 Yes
AA2520 N540 No
AA2520 N135 No
IMR4895 Re15 Yes
IMR4895 Varget No
IMR4895 IMR4064 Yes
IMR4895 H4350 Yes
IMR4895 N540 Yes
H4895 Re15 Yes
N135 N540 OK, No
N135 N140 Yes
N135 N150 Yes
N140 N540 No
N140 H4350 No
N140 Varget No
N540 N550 Yes
N540 IMR4895 No
Re15 N540 Yes, No
Re15 N550 Yes
Re15 N140 No
Re15 Varget No
TAC N135 Yes
TAC N140 Yes
TAC Re15 Yes
TAC IMR4064 Yes
TAC Varget No
Varget N540 No, Sighters low, rest OK.
Varget H4350 Yes
Varget N140 Yes
Varget IMR4064 Yes
WC844 Varget No
WC844 Re15 No
WW748 Re15 No
IMR4064 N150 Yes


From this thread...http://www.usrifleteams.com/forums/index.php?showtopic=14581&hl=compatibilities&st=15 and all credit for this info is given to "becoole"

I 've noticed it before, but usually wrote it off... as one load likes to group at 03:00 o'clock while the other liked 09:00 or 07:00 etc...

Now if this is the source of your issues...............That is for you to decide.  

For me to further opine, I'd like more info from you.............

ie. Distance, rifle, what sort of problems did you see?  etc..

PS........ Each of those authors (and I assume the list creators) were referring to their experiences with the 223 but I would think the same would/could apply to other calibres.