Barrel temperature affecting accuracy

[dlau]

Thanks to everyone for their input and advice.

I got out yesterday to try some things out. First up, no more IVI ball. I brought 150gn Remington FMJ, $13 for a box. Also brought some 7.62 match ammo.

So with a cold barrel at 25 yards, I bore sighted the scope and shot a round of the Remington and hit dead center. So far, so good.

Then at 100 yards, I shot 3 rounds of the match. Finally, a consistent group of 1 1/4" about 3.5" high and 3" right of bull. Didn't expect it to be that far right, but at least I got a consistent group.

I repeated the same with the Remington, and got a very similar 1 1/2" grouping about 2 1/4" high and 1" right. One day I'll figure out how to post a pic of the target.

I was kind of surprised how different ammo would group in a lateral pattern like that.

So the next step is to get some heavier 180gn ammo as suggested and see what that does. I'm determined to get a 1" 6 shot grouping!

 

[Howard]

The vertical line sounds like an ammo prob to me. If it was the barel, the group would not nececarily be vertical. It sounds like the velocities are not concistant so you are getting some shots that drop more than others. The horizontal accuracy attests to the accuracy of the gun. You are only getting .5" of horizontal seperation, and if you get some ammo that your gun likes I immagine your virtical seperation wouldn't be much more. Just my thoughts, and keep the penny.

Could be an ammunition quality control thing (another argument for reloading). But vertical stringing also characterizes the effect of barrel heat. I do alot of shooting and reloading, but none of my rifles has a heavy barrel. So they do heat up, especially in the summertime. Only three-shot groups for me, then some cool-off time. Four-and especially five-shot groups almost always result in the fourth or the fourth and fifth shots creeping up a bit.

 

[dlau]

I took all the great advice from this thread and went out with a box of 180gn Federal and 150gn Remington.

Generally the 180gn grouped about 3" higher at 100 yards, but things did improve with the 180! Once I got into a groove, I managed a 3 shot 3/4" triangle group at 100 (2.5" high of aiming spot), and 2.5" 5 shot group at 200(level with the aiming point).

It was a cool day, so the barrel didn't get as hot as the other days. I did give it at least a minute between shots.

For this rifle and ammunition, I'm guessing these are good results. I figure the next step to improve these results is to handload, but I probably won't get into that this season. However there's lots of room for improvement for this shooter.

Thanks again for all the great advice.