Mixing Different Powder Residue in Barrel

[Lee T.]

I finally got around to reading through the 'Gas Gun Reloading' section in the Sierra manual. An item under Powder caught my attention. It says that if you are testing various loads of different powders, which I've been doing a lot of, residue in the barrel from one type can affect the results of the next types. Barrels should be cleaned between types.

While this makes perfect sense, and probably is well known amongst match shooters, it never occured to me before and it's the first time I actually read it. Call me a novice......but is this something that you all have experienced or heard about? How much can it actually affect accuracy?

Guess I might have to start over, DARN, more shooting!

[madsenshooter]

OMG noooo! There went my plans to pre-foul the bore of my Krag before shooting in the Vintage match next week! I was going to use a load with a different powder and bullet from what I'll be shooting in the match! No really, I think the effects of different powder residue would be minimal, unless you're shooting something like 860 which leaves a lot of residue, before shooting your pet load. Maybe if we were talking about benchrest shooting one could find a bit of an effect.

[p246]

I agree with madsenshooter it would only affect round trajectory ever so slightly, and would probably bother only the most serious benchrest shooter. That being said if your tying to work up loads it does not take long to run a patch. If I was trying to illiminate every small potential issue I'd run a patch every string actually and have.

[Lee T.]

Thanks, replies from experienced reloaders is what I'm hoping for.
From the Sierra maual -
"Powder residue sometimes reacts very badly to a second powder being fired in the same barrel without cleaning"
and
"....isn't restricted to match shooters......If the rifle was not cleaned when switching from one type to another, this may have manifested itself as an accuracy problem. The shooter who is unaware of this phenomenon would have most likely dismissed the later groups as being less accurate than the first one being tested."
Well......that's what it says. Something to keep in mind I guess, and have a rod and a few patches handy. lee

[madsenshooter]

Sierra has that tunnel they shoot down, maybe if we had something like that we'd be able to sort out such subtle differences too. Me, I can't put in the time. You have to clean, then with some rifles, it takes a few shots to get back to the level of accuracy you were previously at, so it isn't just time, it has now became added expense. One doesn't need golf ball sized 100yd groups to hit a deer at 200yd! Actually, when it comes to hunting accuracy, shooting groups is a waste. How often does a rifle shoot that first shot out of a clean barrel somewhere else? The shot that would matter in a hunting situation doesn't hit where the rest of them do. Now I've done it, it's late and I've lost the whole train of thought, off to bed!

[joem]

There might be some difference but if you shoot five or ten shot groups I don't think you could tell any difference after the first two shots.

[Bill H]

I would like to know the page and which manual contains that. I have been reloading for 50 years and never heard that one. As for the first shot out of a clean barrel, that is something which is quite repeatable, but varies quite a bit from gun to gun. Just clean, then fire a round, noting where it lands in relation to the normal group. Some cleaning fluids produce much more change than others.

In my experience, a non oily fluid such as Shooters Choice is the worst, the first round out of my .270 landed 8"high at 100 yds. An oily patch followed by a dry one results in very little change between first and subsequent rounds in most of my rifles.

An "oily" cleaner, such as Hoppes 9 behaves much as oil, so cleaning followed by a dry patch is the best practice in my opinion.

[Lee T.]

Sierra, I think 2003 (the most current version I found). Section on "Gas Gun Reloading" pgs 165-182.
The information and quoted text is under 'Powder Selection' pgs. 174-76.

As I said in the OP, I'd never heard these things either, thus my questions here.
lee

[p246]

I would like to know the page and which manual contains that. I have been reloading for 50 years and never heard that one. As for the first shot out of a clean barrel, that is something which is quite repeatable, but varies quite a bit from gun to gun. Just clean, then fire a round, noting where it lands in relation to the normal group. Some cleaning fluids produce much more change than others.

In my experience, a non oily fluid such as Shooters Choice is the worst, the first round out of my .270 landed 8"high at 100 yds. An oily patch followed by a dry one results in very little change between first and subsequent rounds in most of my rifles.

An "oily" cleaner, such as Hoppes 9 behaves much as oil, so cleaning followed by a dry patch is the best practice in my opinion.

Bill I played with this issue in a 308 heavy barrel and pulled my notes. Cold bore with dry patching after hoppes #9 .5 high 12 o'clock. Hopes wet .65 high 11 o'clock. Kroil dry .5 high 12 o'clock. Kroil we .6 high 12 o'clock. Rem oil dry. 6 high 12 o'clock rem oil wet. 75 high 11 o'clock. All cold bore and repeatable. Ammo was 168 grain federal match. Proved to me to run a dry patch.

[p246]

Sierra, I think 2003 (the most current version I found). Section on "Gas Gun Reloading" pgs 165-182.
The information and quoted text is under 'Powder Selection' pgs. 174-76.

As I said in the OP, I'd never heard these things either, thus my questions here.
lee

Lee I've never done any load developed using different powders in one setting, and my guns are cleaned after each outing. Therefore I can not speak to this. But I see an experiment in the future.