Discard cold bore shot?

[wvfarrier]

I did a search but came up empty.

When you are shooting to test load development, do you discard your cold bore shot?

I ask this because I have noticed that my proof CF 308 barrel has a tendency to send the first shot almost 2" up and left from the rest of the shots. It is so consistant that I can use Kentucky Windage to correct for it most of the time.

Yesterday I tested some 155 TMKs and some 195 TMKs using Varget and BLC(2). I ran the 155s first and got some incredible groups and perhaps the best SD of my life....5! The lowest and highest charge weights shot the best, .301 and .515 respectively. However, on that first shot I did not think to correct for the cold shot and it was a full 2" high and left.

After finishing that string I let the rifle cool for an hour and repeated with the 195s but did compensate for the difference. Boom, it landed dead into the bullseye.

In the future I may just fire a plinking round to settle everything in before proceeding.

 

[Gunfighter14e2]

When switching powders, w/o cleaning yes.

 

[rustyinbend]

I always ignore my first three shots when I'm doing load development. They're just for sight-in and barrel warming.

 

[Maurygold]

Yes on cold bore. Also first 3-5 after a cleaning

 

[slodsm]

I always load 5 extra of my lowest charge during load development. I don’t bother recording speed or looking for groups on those first 5. They are my throw aways so the remainder will be more consistent with what that charge/seating depth/whatever will perform like.

 

[Simonsza1]

2” is a crazy big cold bore shift in my opinion. Don’t know if I’ve ever had a rifle with more then a 1/2” max and that was with a suppressor. Guess thot’s why we test it. If it’s a hunting rifle I would work to change that whether it’s a new barrel, tuning etc.

 

[diggler1833]

It really depends on my barrel. I have a few factory barrels that have a cold bore shift, but it is usually about .1 - .2 mils, and not two inches. Sometimes I have a slower/faster first round on a 'generally cleaned' barrel, but no difference on POI at 100 yards (we're talking 20-30 FPS).

Almost all - if not all - my cut rifled barrels have no noticeable shift (sample size of eight currently). Once I know that no shift exists at 100 yards, I almost never factor a cold bore into load development again...the exception being the velocity of that first round on a CLEAN and cold barrel.

When I thoroughly clean all the way back to bare metal, it has taken a couple rounds to straighten out (1-3 usually).

*But on a fouled cold bore, I'm not seeing any shift. If you've ever been unfortunate enough to watch my rambling and shooting at 650 yards, the first round is always a cold bore. And it has never been the determining factor in my poor performance (that would be me).

At this point OP, I'd be a tad suspicious of either your barrel's stress relief, or how it sits in your stock/chassis.

 

[Simonsza1]

 

[st1650]

One of my barrel threw a very bad cold bore shot every time and it got fixed by using a different muzzle device.

 

[straightshooter1]

I did a search but came up empty.

When you are shooting to test load development, do you discard your cold bore shot?

I ask this because I have noticed that my proof CF 308 barrel has a tendency to send the first shot almost 2" up and left from the rest of the shots. It is so consistant that I can use Kentucky Windage to correct for it most of the time.

Yesterday I tested some 155 TMKs and some 195 TMKs using Varget and BLC(2). I ran the 155s first and got some incredible groups and perhaps the best SD of my life....5! The lowest and highest charge weights shot the best, .301 and .515 respectively. However, on that first shot I did not think to correct for the cold shot and it was a full 2" high and left.

After finishing that string I let the rifle cool for an hour and repeated with the 195s but did compensate for the difference. Boom, it landed dead into the bullseye.

In the future I may just fire a plinking round to settle everything in before proceeding.

For target shooting, yes. . . I always shoot a couple "cold bore sots" before load development, especially after a cleaning.

For a hunting gun, where you want your first shot to be predictable, no! In fact, I want to only doe my load development shots when the bore is cold.