28 Nosler, 150 Grain TTSX

[28gaugewaterswatter]

I am trying to come up with a load for my 28 Nosler, Christensen Ridgeline with 26 inch barrel.
I am using 150 Grain TTSX bullets, CA resident so non lead is required but I also really like the termninal ballistics of the bullet.
Currently using H1000 powder as I had it available at my local shop.
2.83 inches base to OGIVE, 50 thousands from the lands, the gun has a long throat.
I shot a ladder test and found nodes around 79.3 and 80.2 grains. I went with the lower charge to hopefully preserve barrel life as best as possible.
I loaded up 4 round groups of 79.3, 79.4 and 79.2 and shot them round robin, 79.3 had the best es and standard deviation at 6.85 with an average of around 3180.
I loaded up a few more and shot them a few days later,similar weather and conditions. My average velocity jumped up to 3220 and my STD went to 12.52, with an es of 34. including a cold bore shot.
I was double measuring all my loads, so i do not think that I had a change in my powder load.
I have cleaned the bore out after every shooting session and shot a few foulers before each testing session.
I remeasured the bore depth, and found that it is now 12 thousands deeper than I had initially measured, I am not planning on chasing the lands unless necessary.
What am I doing wrong here? Any suggestions on powder change.

 

[Slimfinn]

Were you using virgin or once fired brass?

 

[28gaugewaterswatter]

virgin nosler brass, all inspected and cleaned up before loading if necessary

 

[Yoteklr]

I am trying to come up with a load for my 28 Nosler, Christensen Ridgeline with 26 inch barrel.
I am using 150 Grain TTSX bullets, CA resident so non lead is required but I also really like the termninal ballistics of the bullet.
Currently using H1000 powder as I had it available at my local shop.
2.83 inches base to OGIVE, 50 thousands from the lands, the gun has a long throat.
I shot a ladder test and found nodes around 79.3 and 80.2 grains. I went with the lower charge to hopefully preserve barrel life as best as possible.
I loaded up 4 round groups of 79.3, 79.4 and 79.2 and shot them round robin, 79.3 had the best es and standard deviation at 6.85 with an average of around 3180.
I loaded up a few more and shot them a few days later,similar weather and conditions. My average velocity jumped up to 3220 and my STD went to 12.52, with an es of 34. including a cold bore shot.
I was double measuring all my loads, so i do not think that I had a change in my powder load.
I have cleaned the bore out after every shooting session and shot a few foulers before each testing session.
I remeasured the bore depth, and found that it is now 12 thousands deeper than I had initially measured, I am not planning on chasing the lands unless necessary.
What am I doing wrong here? Any suggestions on powder change.

Was this rifle brand new when you first got the initial BTO measurement? The lands and (thus measurement) will increase fast at first then stabilize at a slower rate of erosion for the next few hundred rounds.
H1000 is going to be the best powder for low bore temperatures. Make absolutely sure you are letting the barrel cool between shots!!! All of my Noslers ( 26,27,28,30) only see cold bore shots...never even three shot strings.
My first 28N lasted for 800 rounds shooting 175gr Elite Hunters with Reloder33 which burns quite a bit hotter thsn H1000. It still shot under one moa but I didn't want to take chance on an errant shot on big game when it counts.
I consider the first barrel i have chambered in a "new to me" cartridge a learning experience. The new 28 Nosler barrel shoots the exact same load.

group shot at 200 yards from a bull bag

 

[28gaugewaterswatter]

Was this rifle brand new when you first got the initial BTO measurement? The lands and (thus measurement) will increase fast at first then stabilize at a slower rate of erosion for the next few hundred rounds.
H1000 is going to be the best powder for low bore temperatures. Make absolutely sure you are letting the barrel cool between shots!!! All of my Noslers ( 26,27,28,30) only see cold bore shots...never even three shot strings.
My first 28N lasted for 800 rounds shooting 175gr Elite Hunters with Reloder33 which burns quite a bit hotter thsn H1000. It still shot under one moa but I didn't want to take chance on an errant shot on big game when it counts.
I consider the first barrel i have chambered in a "new to me" cartridge a learning experience. The new 28 Nosler barrel shoots the exact same load.

group shot at 200 yards from a bull bag
View attachment 27484

It was not brand new, was from the consignment shelf from a shop I would consider family. The previous owner said it had about 50 rounds down the tube. I have been trying to take at least 2 mins between shots to allow cooling