Hot barrel = Accuracy decrease/bullet drift?

[Mossyoakglock]

I went to the range Saturday and Sunday and shot my hunting rifle to make sure it was still zeroed for hunting season. It is a Remington 700 ADL .30-06 that is about 17 years old. It is topped with a Leupold 4-12 x 40. I’m shooting 150 grn Core-Loks as well. The only modification I have done is I replaced the wood stock with a Synthetic stock about 8-10 years ago.

 

In those two days I shot about 30-40 rounds (about 20 each day). After a couple shots, and my barrel heating up, I started to notice that my groupings and shots were starting to drift up and left. I spoke to a few of the RSOs and they said that when sporting barrels heat up, then tend to start drifting up and right which makes sense since it did it consistently both days after the barrel was hot. Could heat, and shooter fatigue, cause that drift?

 

Here are my targets from both days. These are not all the shots I took since I was shooting at two targets both days. All shots were taken from sandbags at 100 yards, so my rifle was anchored solid.

 

This is Saturday's last rounds of the day

 

Shots 1 - 3 where taken with about 2-3 minutes between each shot to let the barrel cool a little. Each time I shot, the barrel was warm to the touch but not hot. Shots 4 & 5 were taken right after shot 3 and there was maybe 1 minute between shots so there was not much time to cool

 

This is Sunday's last target of the day.

 

Shots 1 and 2 were taken with about 2-3 minutes between each shot. I fired shot 2 and then the RSO called the range cold so shot between shot 2 and 3 there was much more time to cool. Maybe 5 minutes.

 

Shots 4-7 were taken maybe a minute after shot 3 with only 30-45 seconds between each shot so there was plenty of heat build up.

 

I did a little research when I got home and from what I found, some barrels will drift/wander and some won't. It depends on bedding, barrel quality, manufacturing process, etc.

 

Am I, and the RSO's, correct in thinking that once the barrel heats up, the shots tend to drift? Maybe even throw in shooter fatigue as well? I shot the Saturday target around 10am. Then went to shoot with my girlfriend's dad around 1pm that day and shot my muzzleloader and AR. Then the Sunday target was shot around 4pm.

 

On a second note, how are the groupings of my first 3 shots? Does it look like I'm dialed in?

[SouthernSilveradoGuy85]

Not really an expert, but I want to say that I don't think you fired enough shots in a quick enough time frame to heat up the barrel enough to make the rifle not as accurate. Even though it's a 30-06. Usually it's the barrels on a full auto or a semi auto that have shot hundreds of rounds in a short time. And when I say short time, I mean all back to back.

[DaveH71]

Yes you are correct, a hot barrel will open up your groups. You should be waiting anywhere from 1 - 2 minutes at least between shots, especially with the large powder load of the .30-06.

 

Read up a little bit on bull weight barrels vs medium contour barrels vs standard contour barrels. A free float barrel will also help with the shot wonder.

Take a dollar bill and wrap it around the barrel at the muzzle end, then slide it down the barrel till its close to the action. The dollar should freely pass down the barrel without touching the stock. If it does touch then you need to sand the stock down at the contact points. Try this when its cold and when its hot from being fired. I'm willing to bet your barrel is coming in contact with the stock at some point.

 

Also keep the barrel nice and clean. A good barrel swab and scrub brush will do it for you. Should be doing a quick cleaning at least after every range trip.

 

Judging by your first 3 shots i probably wouldn't touch anything if this where my hunting rifle. You will never get more then 2 shots at something let alone 4 or 5.

 

Check for proper torque on the action screws to the stock as well, they should be tight but not splitting the stock tight.

[Mossyoakglock]

One of the RSO's did mention that the stock was touching the barrel once it got hot. I'll check it when I get home to see if the barrel is touching the stock when it's cold.

 

I also clean my rifle after every range session as well and the screws have the proper torque based on the information that I got from Remington.

 

I'll probably go shoot it one more time right before rifle starts just to verify.

[carguru]

Another vote for the stock touching the barrel. I have a SPS Varmint that used to drift off after a few shots. All that was fixed once I changed to a stock that free floated the barrel. One thing that you can do to evaluate your rifle is to take a piece of paper or a thin string and slide it between the barrel and stock fore end and see how far down the barrel it can go.

[Mossyoakglock]

I checked the stock and I can easily get a dollar bill between the barrel and the stock except for the very front of the stock. So with that, the barrel was definitely touching the stock when the barrel heated up since it was touching after the range session.

[waumo1]

This behavior is common in rifles especially light barrel profiles. Sometimes free floating the barrel will help sometimes purposely having stock upward pressure at the muzzle end of the stock will help.

 

As another poster said, if that was my hunting rifle and you were shooting at 100 Yards, I would not change it.

[barry G]

this reminds me of m16 training.

 

I was an ace at home, and ran from special forces recruiting..

I chuckled to see the horseshoe shaped barrel they handed me after joining the air force.

With knucklehads accidentally flicking the one switch to automatic, even some getting mad at themselves seeing the sand puffs of going way off..

 

my first and only try got 2 bullets in one hole, with rounds of ten in 3 minutes. I got away...claimed to have missed one.(I won't admit where I got the advice)

 

the purpose of targets is to find what you have found...and go with the gun or against.

even real war guns with auto modes get the same attention.

[wiskey3]

Yes it will. I shoot long distance. With a skinny hunting rifle barrel it will heat up quick (6-8 rnds) is enough to open up your groups and heat up that barrel. However the skinny barrel cool down faster as well. A lot of factors can come into play and there more pronounced the further your shooting. Shoot 3-5 shot strings consecutively without removing your face from a proper cheek weld, then adjust your dope. Let the gun cool for 10-15mins with the bolt open and re check zero. Hope that helps. Safe shooting.

[Spurshot]

Old thread, but a common subject.

 

Hunting rifle accuracy, in a practical sense, can be judged on a set number of shots, estimated to be shot in a given hunting situation. It's very common to have a 3 shot rapid fire assessment for bolt action guns.

 

More than that number of shots becomes progressively less likely for a skilled and conscientious hunter.

[kstruckcountry]

As easy as it is to make sure the stock isn't contacting the barrel, there's really no reason to not fix it.

 

For my .223, hot accuracy is important if I'm going to shoot varmints. It is free floated, heavier barrel profile, and fluted, all of which help. Although how much fluting actually helps with cooling is debatable. I'm working towards a 1" 10 shot group.

 

But with my .30-06, I'm lucky to get 3 shots within 2 inches, haha.

 

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[XSKIER]

If you really want to study the effects of barrel heat induced impact drift, then pick up a <$500, >10 year old mini 14. A five shot group in less than one minutes time is incredibly large (like 6 inches).