Can barrel heat change group size?

[twoworms]

Can barrel heat change group size?

I was shooting my 500S&W Encore again at 50yards and was getting good groups. After about 20 to 24 shots it started going south on me. I stopped shooting and wiped the bore with one dry patch and the barrel looked clean. I then shot 3 shots into a 1.25" group with the next two groups going wild again. I was shooting fast and didn't let the barrel cool I just shot group after group at 50 yards. I was talking with a fellow boolite cast and he questioned the barrel heat and boolit size.

My load was 11.5 grains of Unique and a 450gr GC soft lead boolit lubed LeeAlox. Note there was no leading in the barrel after about 45 rounds but groups had gone wild.

Tim

[1Shirt]

In one word, and in my less than humble opinion-Yep! Sure can! Usually does!
1Shirt!:coffee:

[IcerUSA]

What 1shirt said

[PAT303]

Third that Pat

[randyrat]

Yep, i'll forth that. I had a FAL 308 I couldn't hit a bull in "ars" after 10 rds of a 20 rd mag. I have a single shot handy rifle O6, I let it cool 3-4 min between shots if i'm shooting for accuracy, thats with good heart thumpin loads.

[John Boy]

Yes, even shooting black powder. Worst is a shotgun barrel but patterns don't change. Using single lead projectiles over black, MOA POI can change severely for distances 100yds and longer
Even shooting slowly, the heat of the day will change the MOA settings that were determined when shot on a cool day

[Char-Gar]

The really interesting question would not be "if" barrel heat changes group size? The interesting question would be "why" does barrel heat change group size?

[Scrounger]

One factor that I've thought about is the rising heat waves. And they don't raise straight up, they wiggle left and right on the wind... They have to affect the shooter's perceived aim point, with iron sights and more so with a scope. Shooting the groups with the gun in a machine rest would eliminate this possibility as well as shooter error. You have no idea how bad mirage can be until you look at the steel rams at 500 meters through a 20X scope on a 100 degree day on the California desert.

[Lloyd Smale]

heat changes the way the molecules of steal line up in the barrel and that effects vibrations. It also tends to warp the barrel slightly changeing point of aim. Hows that for technical. Hell i sound like one of the bullet scientist on here! se evin eye can sey somin intelgant. Dont get used to it though!

[Sundogg1911]

I was shooting an AK at the range last winter, as the barrell heated up my shots climbed about 6 inches on the target. The groups stayed fairly tight after the barrell temp. stablized though, but the target looked like I shot a racing stripe in it.

[Lloyd Smale]

if its anything like Michigan it was probably because you got 6 inchs of snow in the time you shot that group!

[twoworms]

Thanks,

I shoot a 260Rem at up to 500meters with a 36X scope, it shoots better with a cold to warm barrel. Heat opens the groups up a bit at long range. For some reason I just didn't think a big fat 450gr cast boolit would change much at 50 yards. Maybe you guys are right and I need to slow down and let the barrel cool. I'll tell the wife I need to spend more time at the shooting range... :)

Tim

[Hi-Standard]

I've got a Remington 700 SPS in 30-06 that can have two holes touching at 100 yrds. Then on shot number 3 the groups start to look like my 1100 using number 9 shot!

[Ricochet]

I've got a Remington 700 SPS in 30-06 that can have two holes touching at 100 yrds. Then on shot number 3 the groups start to look like my 1100 using number 9 shot!
I don't have a Remington 700, but none of my rifles will shoot #9 shot worth a toot. :mrgreen: