Head scratcher

[Gobears16]

So I’m doing load work for my 28nosler and I’m scratching my head today... I started with 4 round with loads starting at 82.8, 83.1, 83.4.

82.8: 2976, 2977, 2978, 2975
83.1: 3008, 2994, 3001, 3006
83.4: 3019, 3021, 3037, 3025

The group with 82.8 looked great so I ran back and loaded up four more at 82.8. So I head back out and shoot... 2946, 2948, 2948, 2944.... accuracy was still great but how come the 30fps drop? This was all done within 1hr of shooting first group. I’m loving the low ES but can’t figure out why the drop when the conditions were the exact same. Anybody have any remedies or thoughts?

 

[Dthomas3523]

Are you absolutely sure you loaded the correct charge weight?

Also, don’t worry what the groups look like for a charge weight. You can make the group as good or bad as you want with seating depth.

 

[Dthomas3523]

And what chrono?

 

[Tokay444]

Leave them in the sun. They’ll speed up again.

 

[918v]

Optical chrono?

 

[Gobears16]

Are you absolutely sure you loaded the correct charge weight?

Also, don’t worry what the groups look like for a charge weight. You can make the group as good or bad as you want with seating depth.

Positive I used the same charge weight. I’m using a RCBS lite for scale. I’m using a labradar for chrono.

 

[Gobears16]

Leave them in the sun. They’ll speed up again.

that might the answer. I’m using RL -33 and I’ve heard it’s not very temp stable, but the outside temp was the same the entire time (78-80).

 

[PinesAndProjectiles]

that might the answer. I’m using RL -33 and I’ve heard it’s not very temp stable, but the outside temp was the same the entire time (78-80).

You loaded up the first batch, then shot them. How long between the loading and the shooting?

Were the first rounds fired in the sun longer than the next batch?

 

[918v]

Hot barrel vs cold barrel 1 hour later?

 

[Gobears16]

20min from the first batch loaded to firing first round. I took about 20-30 to fire those 12 shot. The rounds were sitting on bench in the sun. Went back to the shop loaded up 4 at 82.8 and fired those 10 min later.

 

[Gobears16]

Hot barrel vs cold barrel 1 hour later?

all the shots were 3-4 minutes apart. I set a timer on my phone for 3min so I don’t over hear the barrel to much. The time from my last shot and firing the second batch was probably 20 minutes

 

[Dthomas3523]

Load two more volleys. Leave on in heat and other in car in the AC.

That’ll show you if it was the issue. At this point, it’s the only one that makes sense.

 

[Seymour Fish]

20min from the first batch loaded to firing first round. I took about 20-30 to fire those 12 shot. The rounds were sitting on bench in the sun. Went back to the shop loaded up 4 at 82.8 and fired those 10 min later.

Bears, how long did the first load sit in the sun before being shot ?

 

[spife7980]

Now load up 8 at the same time but only shoot 4 now and 4 later.

You’ll find that the shit that crazy shit is actually happening all the time and the real spread is much wider than what a small sample says. And sometimes there is no explanation to be found.

Did you adjust the radar any? If found if I don’t point it right I can influence the reading. And the 6-12,12-18 whatever settings are important. It’s generally pretty forgiving if you give it the slightest attention but I have found that I got sloppy in setting up.

 

[Gobears16]

Now load up 8 at the same time but only shoot 4 now and 4 later.

You’ll find that the shit that crazy shit is actually happening all the time and the real spread is much wider than what a small sample says. And sometimes there is no explanation to be found.

Did you adjust the radar any? If found if I don’t point it right I can influence the reading. And the 6-12,12-18 whatever settings are important. It’s generally pretty forgiving if you give it the slightest attention but I have found that I got sloppy in setting up.

thank you for the helpful info. I never thought about the settings. I’ve had a love hate relationship with the labradar. I love the easy read out but the interface sucks and way to many buttons to press to get to different screens.

I’ll load up 8 more and leave some in the truck with the AC on and shoot 4 after they’ve been in the sun.

it’s just weird to me that both 82.8 groups had extremely low ES but 30fps different. That’s what was throwing me off. This is my long range hunting rig so I’m not to concerned with high speed. I just want very repeatable results.

 

[Seymour Fish]

Could simply acquire DOPE

 

[Sirshredalot]

Did you load the same brass(same actual cases, not same lot)? Once fired?
spitballing

shred

 

[hafejd30]

The heat in the sun seems the most obvious

Was this brass that was all sized together? As in not brand new Lapua brass with .003 neck tension vs once fired brass with .0015 neck tension? Factory vs fire formed.

Same Primers?