Accuracy changes from switching bullets

[PAshooter20BR]

I have a proven load I shoot in my 6.5x47 which typically shoots under 1 inch at 300 yards. I have been doing some expirementing with 140 Bergers and the same powder, H4350. I had about 24 rounds of the experimental berger load through the barrel and haven't been having much luck, about half Moa. I pulled three of my go to 120 nosler load and they shot a 4 inch group at 300. Can changing bullets without cleaning give erratic accuracy until things settle back in? I am out of loaded rounds so couldn't shoot a second group.
Thanks

 

[Mikemci]

I have been told that whenever you switch powders, you should clean the barrel. Maybe others will give their experiences. I would like to know if it's true and why it matters.

 

[Shaggy357]

How many rounds do you normally shoot when you get the 1" groups at 300? The two different bullet brands likely have different bearing surfaces which could leave different amounts of copper in the bore and maybe different amounts of powder residue. I think Mike is probably right on with his comment on cleaning the barrel......

 

[Zero333]

Sometimes you have to clean the barrel or shoot a few groups before things settle when changing loads. But not always.

In your case it's obvious a cleaning is warranted.

 

[Shynloco]

I have been told that whenever you switch powders, you should clean the barrel. Maybe others will give their experiences. I would like to know if it's true and why it matters.

More so true in Rimfire than Centerfire loads. But it also depends on the barrel, it's cleanliness and number of rounds down the tube. But generally speaking, if you don't clean when changing powders, it'll take anywhere from 5-10 rds for the barrel to settle in with a different powder load. At least thats my experience. But even a dry patch or two helps the transition in powders. I can't give you a technical reason other than its the nature of the beast.

Alex

 

[PAshooter20BR]

Typically clean every 25 to 30 rounds, no difference this time other than 25 different bullets that went down the barre prior to my go to load shooting poorly. same lot of h4350 in both loads. Cleaned gun when I got it home Sunday. Will shoot a fouler and a group this weekend and see what happens.

 

[MislMan]

I would think this is more related to the ogive shape being different between the bullets (Nosler vs Berger). This would cause different jump to the lands. Also, some bullet designs are more tolerant to jump distance than others.