Cold bore accuracy?

[284 Win.]

Hello everyone,
I was want to know what makes a rifle shoot bulls eye the first 2 shots but after the barrel gets hot, the groups open up about 2". Its like the POI is moving. The first two seams to always hit dead on. Barrel is light .560 at muzzel. Its 6mm Remington. Anyone have a clue.
Thanks Anthony

 

[Korhil78]

There are a lot of things that can be going on. If you think that it is a heating issue, then let the gun cool all the way down after every shot and see if that changes anything. It might be that you have a slight flinch (maybe not). Let one of your buddies that you shoot with take three shots and see. Does it shoot 2 dead on and then the third one off EVERY time or does it vary?

Other questions that come to mind:

Is it bedded?

Is it a free floating barrel?

I know it is annoying that the 3rd one is off but if you think about it when you are hunting you are always taking a cold bore shot. If your first two shots out of a cold barrel are dead on, you might be better off haha. I know..I know..I want mine shooting consistently also but it is an interesting thought.

 

[284 Win.]

Barrel is bedded and the rifle is about 50 years old. As the barrel heats, which it does quick. Quick like 3 shots.

The hotter it gets the worse it shoots. I was just wondering why?

 

[Korhil78]

Any gun you shoot is going to get less and less accurate the hotter the barrel gets. As the gun heats up, the metal inside of the barrel expands and can change the point of impact on a bullet because the inside of the barrel has changed its dimensions. Barrels heat up and cool down at different rates depending on the diameter of the barrel. A thin barrel is going to heat up quicker than a thicker barrel but will cool down faster. They make varmint rifles with thick barrels because people who shoot varmints shoot a lot of rounds in a sitting especially if they are groundhog hunting. The thick barrel takes longer to heat up because it dissipates the heat throughout the whole barrel BUT it takes longer for it to cool down. Anyone with more experience than me can chime in and correct me if I am wrong but I believe that is how it works.

If you want to shoot for accuracy, you will let your gun cool down between every shot.

 

[WildRose]

Sounds like the barrel needs to be completely free floated. If the action is properly bedded that's the most likely culprit.

Also you need to make sure the action screws are torqued properly to the same tension. If they are not heating can cause the action to expand unevenly.

 

[284 Win.]

Rifle is bedded and barrel is free floated. Action screws? Well- I need to look at that again because its a Remington 600 action and it has that small rear action screw and the front action screw is way bigger. So when torqueing the screws I kinda go light on the rear because it feels like i might ring the head of the screw off.

 

[Boss Hoss]

Most of the time in a factory rifle there is not much you can do. Stress in the steel tends to manifest itself as movement as heat builds.

I thought this was just something you just had to live with until the various causes were pointed out to me and by building rifles correctly out of properly stress relieved components would prevent this.

 

[284 Win.]

Thanks everyone for all the info.
Boss Hog, I think your on the right page with the stress relieved barrel. I had Gregg Tannel built me a 6 Dash with a light barrel at 26" long and it would just flat out shot at 500 yards in 100 degree weather. I guess its all about have good hard ware.

 

[hatfield954]

I guess in a real hunting situation, a rifle being more accurate with a cold barrel would not exactly be a bad thing. Unless you couldn't take your game with just one shot. If you had to take more than one follow up shot, then that's when the game would change to the advantage of the animal you were shooting at. If you are like me, then it just wouldn't do. I am picky and want the round to hit near dead center every time and even I know that things just aren't that perfect. There are too many variables involved when it comes to shooting. Good luck with this one, I been there before.