what happends with warm barrel

[04jeep]

Shot today with knight after about 10 shots was doing will then my shot started go up is that norm with hot barrel ? need some help shot group was 1inch high at 100 the it went to about 2.5 from there..

[sabotloader]

04jeep

A warm barrel can definitely cause some accuracy changes. When the barrel is warm it can effect how the sabot turns in the lands and grooves and the shot at POI will move around.

You indicate or I think you are indicating that your projectiles moved up the target - possibly verticle stringing. That usually indicates the warming and expanding barrel is contacting the stock at some point and pushing it way away from the stock.

I do not know if your barrel is a floating barrel or not but you might try sliding a dollar bill under the barrel and between your the forend of your stock. Just check and see if the brrel is contacting the stock in different places...

What kind of rifle are you shooting?

[cayugad]

If possible, let the barrel cool between shots. Swab it good, and then set it off in the shade or somewhere it can cool down. Normally that will help. On real hot days, I take a couple rifles to the range and change off between them.

[halfbakedi420]

sounds normal, happens here.
i usually take 5-12 rifles at a time to go shoot...it cost $10 to get in so i wanna get my $$$ worth anyways,
but definitely waitng between sets and shootin somethin else is a good idea...
also, the 1st shot outta each rifle, use a new bull/target...
keep it in the case with that rifle, as this is good info for later
, cause i dont know about you, but i aint usually crackin 3 shots off in a row opening day, and those 1-3 inches of a cold bore shot can mean everything., just like if its too hot.....

the dollar bill idea is a good one thx fer that, never thought the stock would arc the barrel up!

[04jeep]

Was shooting 250gr thor bullets ill try it again next week to see how it does with clean bore and wait between shots by the way was using 110gr of bh 209 and them thor do shoot nice had 2 almost in same hole at 100yards

[Chasam60]

The POI on my Omega will change on the third shot.Let it cool,and it is right back to zero.My hunting load is sighted on a cold clean barrel.You only get one shot in the woods.

Charlie

[bronko22000]

A lot of things happen when a barrel gets hot. POI being one of them. Now a lot of people think that this is always caused by the warm barrel expanding and touching the stock. And this is true. But another cause is that as the barrel heats up and expands, the bore also gets tighter. This causes higher pressures and can also change POI. Remember expansion works both ways. Makes an inside diameter smaller and makes an outside diameter larger. Now we're only talking a thousandth of an inch or so. But it doesn't take much.

[ronlaughlin]

Originally Posted by bronko22000

.......................Remember expansion works both ways. Makes an inside diameter smaller and makes an outside diameter larger.........................

When installing bearings on a shaft without the proper tools, one trick is to heat the bearing so that it is easier to install. This indicates the inside diameter of the bearing gets larger with heat, not smaller.

[bronko22000]

Ron come to think of it you are right. I stand corrected. I do recall now that when installing a tight press fit, we would heat the larger piece and soak the piece to be inserted into liquid nitrogen to drop the temp. Then hope it was aligned and installed quickly.

[Chasam60]

You guys got that right. Try installing a class 3 Timken bearing with a 5" ID without heating it. Let me tell you it just don't work. We used a 250 deg temple stick and heavy gloves-installed them by hand-better be quick though. The fire control computer on an Abrams tank compensates for barrel temp.

Charlie