Sighting in and barrel heat

[bessiedog]

So... little help with info needed here.

I just got my savage 110 7mmrm back.. but took off and refinished the stock on it (no more stupid shiney finish).

By boy is going to use it this year ... he’s a good shot and he’s been shooting a 308 and a 30-06 for 5 years now sooo...

I figured I’d get him to run the rifle while we re sighted the scope in (old Ruko 3-9.. but it’s still serviceable).

After 6 shots at 50 yards we were 1.5 inches right and dead on.

I moved us to 100 yards... and between me and him shooting.. and adjusting the scope... we are now about 2 to 3 inches left and dead on.

I ran out of ammo.

My question is.... we were waiting about 3-4 minutes between 3 group shots to cool down the barrel (she gets hot hot).

My question is... how much can barrel heat affect accuracy at 100 yards?

[elkhunter11]

It depends on whether the rifle has bedding issues, or if the barrel has stresses that cause it to move when it heats up. I have seen 3-4" at 100 yards. When doing a sight in, I shoot a group from a cold barrel, then let the barrel fully cool, as that is what you will have while hunting. If the poi moves during a group, then the rifle has issues. As well, letting a round sit in a hot chamber for a few minutes will heat up the powder charge, which can cause a change in poi, so I chamber and fire the rounds with no waiting between the shots of a group. If you are trying to do a sight in with a hot barrel, you are quite possibly wasting your time and ammunition.

[bessiedog]

Thanks Elk

Quite honestly there were way too many variables at play here obviously to narrow it down.

This rifle is for hunting, the goal is to hit pie plate or better accuracy by the boy to 300yards by summers end.

This gun was very capable of doing it before the stock refinishing..... so I’m fairly confident we’ll get there.

I’ll bring the 22s and my 303 and 3030 so we can play a bit while the 7mm cools down next time.

[elkhunter11]

For me, typical sight in for a newly mounted scope is bore sight, and fire one round at 100m. Then it's a scope adjustment and a three shot group. Then it's a fine scope adjustment , and with a cool barrel one more three shot group to confirm zero. And I do a final three shot confirmation in cool weather, just before the hunting season opens for me. I see people using a box or two of ammunition to do a sight in, but it isn't required, and the result is usually not that good when it does happen.

[bessiedog]

Thanks again.

I tend to do something fairly similar (especially in the fall), but I let the boy shoot to get used to it as well..., this increased the amount of rounds used.... and got me thinkin about barrel heat.


And yea..... there’s that little variable of a 15 year old boy shootin a 7mmrm for the first time might be a variable..... heh..

[W921]

I'm lucky to be able to shoot from home.
I always sight in prone.
Depending on the gun but I generally used to fire a 5 shot group. Then that was it until the next day.
I would keep notes on wind,weather, etc.
If you fire 3 shot groups. Use the same target on the second and third day and dont be surprised if your group opens up.
I think factories sometimes straighten warped barrels. Then when they heat up they tend to bend back again??

[260 Rem]

I do my hunting zero close to the time I will be hunting. Rifle and ammo are left in the vehicle parked outside overnight ... then to the Range. I use one target for the cold bore round and follow up with a group on a second target for practice. Same routine on Range days following so at the end of five days, I have a five round group on the cold bore target. That gives me confidence that the POI will be on the money when it counts.
As mentioned by Elk, how the barrel reacts to heat depends on how well it has been stress relieved. Only way to determine if heat affects POI is by trial.