Last year, after shooting many different brands of ammo, I found that my .30-06 consistentlypreferred 165-168 grain bullets over 180's.

This Spring, the same rifle prefers 180's over the smaller guys. I'm the same guy I was, or so I think, so I'd like to take myself out of the equation.

The rifle has had a trigger job, and I've mounted a new scope on it. However, I don't see how these factors would have anything to do with the change in the groupings.

I have begun using bore foam for cleanings. Would this be enough to do it?

Curiously yours,

FC

Are the BRANDS of ammo the same as when you tested last year? I've had same weight but different brands shoot waaaaay different.

The cleaner could make some difference as well as the lot numbers of compoments. Yoiu are a year older too.

James B makes a very good point concerning the lot numbers of the ammo. When those numbers change, it can often have a dramatic effect on how one lot shoots compared to the lot nos. you had been using.
This is just one more reason we take up handloading. You can control uniformity.

Lots (manufacturing runs) of different ammo shoot diff. You could also be getting a build up of copper in your barrel. I still have to use a copper solvent after the foam cleaning. My preference so far is barns copper solvent. You mentioned a trigger job. If that was since last season, the smith retightened the action screws. That can change the harmonics of your rifle and thus the change in groups.

mello

Ooooh, I like that one! Sounds not only plausible, but sensical, too.

Yes, the lot numbers on the ammo are the same. In fact, some of it is from the same boxes.

When it comes to copper, I likely have less than last year. When I clean, I'll let the foam sit as long as overnight, with the barrel plugged, andI'll do it several times. When I subsequentlyuse Shooter's Choice copper remover, there's no blue on the patches whatsoever.

For me, it's actually been a good thing, as I'd rather shoot the 180's if they'll group well.

Thanks for your input!

FC

So far as why??? dangifino...

But, I too have seen this...I just changed to the other weight/brand and kept using...

Just trying to help. The action screws on my Ruger are finicky and the same thing threw a friends Remington off also, neither are bedded though. Which foam are you using? I hate scrubbing copper.

mello

the only thing i can think of is that you were using mtwo different brands of ammo

Even the same brand can shoot differently in the same weight, if the bullet types are different or if the lot#s are different.