Switching between powders, is accuracy affected?

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flyinlead

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I was recently reading the Varmint Al website and in the shooting section I believe, came across something I must ask about.

He claims that your barrel "gets used to" the powder you are using because it fouls in a certain way. So apparently if you switch to a different load with a differernt powder, the first few shots will not be as accurate as they should be, not until the new powder "settles in", in its unique manner.

Is this true, and have any of you personally experienced it?

If so to what extent does it open the groups in precision rifles? Are we talking 1/4 moa to 1/2, or much worse, or hardly at all?
 
I haven't noticed that much when switching only powders. I have noticed it when switching between coated and non coated bullets, especially with rimfires.
 
alot of barrels need to be fouled befor they shoot their best, when you clean a barrel it shoots differently for those first few shots, my guess is the auther cleaned his barrel between switching powders..

the speed of the bullet travleing down the barrel , changes how the barrel occilates, this occilation will effect accuracy...

example, 42.5gns of varget will shoot differently of 42.5gns of 748 as the bullet velocity will be different due to the powders burn rates
 
I believe there is something to this, but why dont you find out for sure? Find several loads with different powders that shoot good groups. Clean your barrel, shoot enough 5 shot groups of load A to eliminate the effect of the cleaning, switch to group B, shoot 2 or 3 groups, switch to load C and so on. If the load B groups shrink in size, you may be on to something. It is a good excise for some range time, let us know how it works.
 
"...your barrel "gets used to" the powder..." It's nonsense. Rifles do prefer one load/bullet/bullet weight over another. And the theory is that if you change powder lots of the same powder, you need to work up the load again. But to suggest the powder needs to 'settle in' is daft.
 
I do this often, as in shoot multiple powders with the same or different bullets. On some range visits I'm working up a new load, same bullet but with a different powder (e.g. BL-C2) and also bring a known good load (e.g. Benchmark) that I've already established. With my factory setup I haven't noticed any accuracy difference returning to my good load but maybe one would with a good aftermarket barrel.

I have heard something to this effect with swicthing rimfire ammo but again, I'd guess it would take a pretty top level gun to notice it.

Steve
 
I have seen the effect where firing a single base powder after a double base powder increased the velocity and pressure for a few rounds. I made the mistake of trying to alternate between the two during a temperature tests.
 
For sure a change of bullets can result in a few fliers untill the bbl copper fouls with the new jacket material.

I have also suspected changing from IMR 4064 to R15 and back again in the 308 to produce a flier or two for the first rounds sometimes.
 
Rite on.

Out to do some shooting right now. Using my trusty hand loads. Picked up a box of factory ammo to take a look at this theory. Figured why not. It's kinda intresting and I have a clean bore.
 
I know that when ever I am testing a series of different powders with the same bullet, the first bullet with a new powder, and sometimes the second hits out side the rest of the group. Not always,but the vast majority of the time. This happens to at least 80%+ of all rifles I have ever shot and reloaded for.

Example:
If I fire 5 shots with my favorite load for my 300WinMag. The group is about the normal size I expect to see. I then load 5 rounds into the magazine that has the same bullet, but a different powder type. The first shot, and sometimes the second will group together. But the next 3 rounds (shots 3,4,5) group in a slightly different location on the target. This second grouping is usually less than 1.5" away from the first shot or two. If I wait for the barrel to cool, I then shoot 5 more rounds at a different target with the same load to prove the group/load. Thats why I typically load 10 rounds for each test. I continue with this routine with all the test loads.

If I intend to shoot my favorite load again afterwards, the first one or two rounds of that load will also hit a different point of impact than it did just before I started testing the different powders. After these first one/two rounds the favorite load, it is printing where it is supposed to be on the target. The next series of groups I shoot after that with my favoite load averages in the normal grouping sizes.
This has been the trend I have noticed for close to 27 years of reloading/shooting. Many different types of rifles,many different calibers. Again I say that this happens the vast majority of the time, but not always.
Try it, and see if what I said is true for you.
I used to get frustrated when I would shoot a test load and always have it group poorly. Then if I had a few extra rounds left, i would shoot them off just to get rid of them and wind up with a good group all of a sudden.
My belief is that when ever you shoot a new powder in a barrel, it take one or two rounds to leave the characteristic fouling that is unique for that combination. Every subsequent round after that is encountering the same conditions round after round. The same thing seems to happen when you fire the first few rounds from a clean barrel. The subsequent rounds fire much more consistantly(velocity etc.).
Thats my .02, or .04, or uhhhh maybe .06 cents worth. LOL! Tell me what you think guys. I am open to other theories or ideas. Have fun and straight shoot'in!
 
I just shot and gave this a try with my hand loads vs some factory loads, different bullets powder and brass. Never really had any huge flyers.
 
You can imagine the frustration of thinking that the first few flyers are the result of a poor load! You could try a hundred different loads and come up the same. One or two flyers and a decent group with a few. Some times it isnt a big flyer, but you will see a trend normally. I hope this helps a few guys out there! Have fun and straight shoot'in!
 
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AKD, thanks for trying that little experiment, its good to hear the results.

My guess is that there may well be something to this, but it probably only has a small effect.

dthunter, sounds like you are speaking from quite a bit of experience as I think this Varmint Al fellow is as well. And it seems you have noticed this consistently. It would be frusterating indeed. When you say the first couple rounds would fall under 1.5" away from the rest of the group, what kind of distance are you shooting at? Just trying to get an idea of the scale of things here.
 
I have had real issues testing 308's using Re15, Varget, 4064 and 748 in series. I have had to scrub the barrels of several rifles for hours to get the fouling out before they would shoot again. Cost me several barrels before I figured out what was happening. I believe 748 is the primary culprit and there is a real interaction between that fouling and Varget. I did a test series using these powders and light bullets in my 338 which was a tack driver and within about 20 rounds was having problems shooting even loose groups. Took many hours to get that rifle shooting again. The fouling is very hard and difficult to remove. Cost me a lot of money over the years. Steve
 
hello flyinlead! The distance is basiclly 100yds. This has been my standard testing distance for initial load evaluation. The 1.5" value is very generalized mind you. The real point is that the first one or two rounds "normally" do not group in tight with the subsequent rounds(3,4,5...etc). If the loads consistancy is truly poor, the spread between the first and/or second bullet will be greater than a load that tends to be more precise. That was a mouthful LOL! I have shot hundreds of groups and discontinued trying to tune them because I thought the first and/or second shot was an indicator of poor performance of the load. Allot of wasted time at the bench! But I eventually learned. Once I figured it out, my average 'testing' group size started to shrink. That really boosted my confidence! And that makes you shoot better as well.
Just keep an open eye and mind for that tendency when trying new loads. I just fire the first two into the target or into the backstop. If i shoot them on target, I normally ignore thier impact placement. Let the barrel cool for a few minutes, Then I shoot my 5 shot group. Thats the one I evaluate.
Have fun you gunnutz! And straight shoot'in!
 
Hello SteveB! It is amazing how some combinations will cause so much havoc! I am lucky that I havent encountered that....yet! LOL! Out of curiosity, how has the varget worked for you in your .308win? I have had great success with Varget. So much so, I have for the most part stopped experimenting with other powders in my .308. Now I'm just shhotin and havin fun. I still need to confirm my trajectory calibrations with my 168gr.Berger VLD's. I want to see how they do out to the limmit of my scopes verticle adjustment. I'm guessing about 1100-1150ish. Hopefully they stay point forward all the way out there. Have fun SteveB and hopefully your "foul"...ing problems are no more.
 
Really wana get rid of that flyer? Replace ur barrel with a good one like a krieger.

I test most of my loads at 600y. 300 & 200 depending on transportation.

Good luck with the 168 bergers. I still have half a box if u want them. What's ur .308' twist? Try the 185 vld's much better. And I agree with varget. I don't use anything elce anymore either.
 
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