I went to the range Saturday to work with some loads I had put together...some worked, some didn't.

Anyway, in my .300 Winchester I was shooting IMR 4831 behind 180 grain Swift Scirocco II's. I fired 10 rounds total. I would like to try a different powder (H1000) behind the same bullet.

In my .257 Weatherby Mag I was shooting IMR 7828 behind 100 grain Barnes TSX's. I fired 16 rounds total. I would like to try a different powder (either IMR 4831 or H1000) behind the same bullet.

My question is:

Where all I am changing is the powder and I haven't fired all that many rounds through either gun, do I need to clean the barrels before I try the next go around?

Thanks.

If you want the comparison to mean anything, and assuming you had a clean barrel at the beginning of the IMR 4831 string, I would start the H1000 string in the exact same condition as the first.

With my 300 Win Mag, I had much better performance and accuracy with H4831SC than either IMR 4831 or H1000. Which is neither here nor their with respect to your rifle... your mileage may vary.

I do a "mild" cleaning after every 6 rounds, if I am using the same powder. the first round after the cleaning is a fouling shot.

A "mild cleaning" is simply running a brass brush down the bore several times followed by a dry patch.

If I am changing powders, then I do a "thorough cleaning". That is, I run a brass brush with a solvent several times, then wet patches with a solvent several times, and follow that with dry patches.

It's times like that when I love to have my boresnake along. I take a swipe or two when changing recipes. Probably not as great as a really thorough cleaning but I believe with a good gun they will keep you shooting good groups ALOT LONGER.
I've also noticed that if I take 2 swipes down a warm barrel at the end of the day I can go home and spray in wipout immediately and get really fast results.
I would say that if your gun doesn't like a recipe after 10-20 shots of something else and then a swipe of a boresnake.....it's too fussy of a load to trust anyhow.

I'm with the other guys here.

If you want a true comparison, you've got to start the loads on equal footing. That is, a clean, dry, unfouled bore.

Some rifles shoot best right off the bat, others like a little fouling before they settle in. If yours likes fouling, how do you know if it's your new load, or the last loads accumulated fouling that is helping it to shoot better?

Also, some High Power guys did tests a while back when shooting different loads at different stages/yardages. Some found that certain powders were more "compatible" with others, while some HATED being shot over a different powders fouling.

I clean after every five shot group. Then shoot one fouling shot and start the next five shot group.

I take a bore snake with me along with 4-5 different loads. start with a clean barrel try your first load for group then clean with the snake. and try your next ect ect the snake is easy to use and you dont have to carry all your cleaning stuff to the range then you can clean it good at home when your done.
I had great luck with H4831sc with 165gr hornady sst