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.

 

[wvfarrier]

I have been on a rampage with 308 Win lately.

195 Sierra TMK
Big Horn Origin with 20" barrel
Varget (hot)
CCI #450 Small Rifle Primers
Starline Small Rifle Primer
Annealed
Several of these loads shot amazingly well but all were compressed and well over book max.

#1- Averaged 2605fps and .30" 5 shot group (No pressure)

#2- Averaged 2614fps and .65" 5 shot group (No Pressure)

#3- Averaged 2627fps and .88" 5 shot group (Very faint ejector mark)

#4- Averaged 2635fps and .55" 5 shot group (Again faint ejector mark)

#5- Averaged 2644fps and .23" 5 shot group (Ejector mark and at the very top of the bolt lift it was mildly sticky).

I quit at group number 5 and will not repeat that loading. It still puts this loads well into/equal too 30-06 loads.

According to strelok, load #1 is:
3.3" low at 300 @ 2286fps with
2263 ftlbs
7.7" low at 400 @ 2106fps with
1921 ftlbs
11" low at 500 @ 1911fps with
1716 ftlbs

 

[st1650]

I have been on a rampage with 308 Win lately.

195 Sierra TMK
Big Horn Origin with 20" barrel
Varget (hot)
CCI #450 Small Rifle Primers
Starline Small Rifle Primer
Annealed
Several of these loads shot amazingly well but all were compressed and well over book max.

#1- Averaged 2605fps and .30" 5 shot group (No pressure)

#2- Averaged 2614fps and .65" 5 shot group (No Pressure)

#3- Averaged 2627fps and .88" 5 shot group (Very faint ejector mark)

#4- Averaged 2635fps and .55" 5 shot group (Again faint ejector mark)

#5- Averaged 2644fps and .23" 5 shot group (Ejector mark and at the very top of the bolt lift it was mildly sticky).

I quit at group number 5 and will not repeat that loading. It still puts this loads well into/equal too 30-06 loads.

According to strelok, load #1 is:
3.3" low at 300 @ 2286fps with
2263 ftlbs
7.7" low at 400 @ 2106fps with
1921 ftlbs
11" low at 500 @ 1911fps with
1716 ftlbs

What’s your coal with the 195 tmk ?

 

[Mike278th]

I have confirmed by chronograph that my first shot after a thorough cleaning is WAY down on velocity. Add barrel harmonics into that and I could see some outliers from the first couple of shots. I usually burn up about three foulers before I start counting numbers

 

[wvfarrier]

What’s your coal with the 195 tmk ?

2.86"
The MDT mags allow a smidge longer but this keeps me just off the lands and these tmks seem to like it.

 

[Mean_Man]

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.

Nope. Speaking for myself, unless I just cleaned the barrel and it’s got no fouling in it really. (I don’t clean to spotless but do use copper fouling remover after each outing.

Except for that first shot after cleaning, everything counts. And I usually fire one just cause after I clean it then put it away. In fact I very seriously care about cold bore shots.

But then my rifle isn’t for just shooting paper or steel.