Altitude:

[Pete Wass]

It has been my experience that altitude greatly changes the tune of a rifle. I first experienced this when I traveled to Iowa to compete in the Nationals. I went pre-loaded and with a Tuner on my 30 BR.

I found when practicing that my rile was shooting a buckshot pattern. I could not readily correct the situation with the tuner so removed it and went about changing the seating depth, testing with a plain barrel. I was able to find a round hole as I usually can with a different seating depth.

In trying to find out why, I discovered that range in Iowa was around 1000 ASL and my testing was done near Sea Level. I have observed similar results with Rimfire Rifles as have friends of mine. Have others experienced the same?

Pete

 

[Dusty Stevens]

Less pressure and more velocity

 

[Pete Wass]

I once bought one of those barrels

Absolutely, I've found the difference and mentioned it before.
More importantly, Dan Lilja has mentioned it. He will tell you the need for different twist barrels for different elevations.

that wouldn't shoot competitively. He told me it was the fault of the twist. Wonder why he makes and sells them if he knows they don't work?

Pete