Nosler 150 ABLR in 6.5 PRC

[Harvey_NW]

I shot the Nosler recommended load today, 61.0 grains Magnum with the 150 ABLR's, Fed 210's, new Lapua cases that i should have sized, the necks were way too tight. 7/8" group with the first load tried. 0.050" from the lands. Tried farther from lands and accuracy dropped off. Never tried closer, will next time.
I have never had a load shoot such a different speed than the data said though. Average 2870 fps. 24" barrel, cold (4 Celsius/39 American), 95% humidity, seated far from lands, 800 ft. elevation. I guess it all adds up, but over 200 fps?? Does this sound right? Has anyone had this kind of a variance from a published load? The node was really nice and small, 19fps variance max across 9 shots, plus one outlier. Its got me motivated to tune this load.

Factory Tikka barrel? They're notorious for being slow.

I'll digress from responding to the rest..

 

[Coreyamyas]

CA Ridgeline, factory barrel.

 

[Harvey_NW]

CA Ridgeline, factory barrel.

What's the round count?

 

[Coreyamyas]

Getting close to 80 now. Does that matter? I've never had a new gun before.

 

[Harvey_NW]

Getting close to 80 now. Does that matter? I've never had a new gun before.

Yes, that could be part of why it's a little slower. Typically within the first 100-200 rounds firecracking will start to develop and speed will increase for a given load. You also may see a little bit of increase once brass is fireformed to your chamber. But there's still a direct correlation between pressure and velocity, so you may get pressure signs and have to back the charge off anyway.

Even if that's not the case, if your chrono is proven accurate 200 fps isn't an unreasonable difference with how many factors there are. Figure the pressure test barrel was well broken in and a fast barrel, yours is new and maybe slower, different powder lots, Magnum is a ball powder and probably fairly temp sensitive, 39° is probably significantly colder than what that data was produced in, etc.

 

[Coreyamyas]

Thank you very much for the help! Much appreciated

 

[ThorM465]

I shot the Nosler recommended load today, 61.0 grains Magnum with the 150 ABLR's, Fed 210's, new Lapua cases that i should have sized, the necks were way too tight. 7/8" group with the first load tried. 0.050" from the lands. Tried farther from lands and accuracy dropped off. Never tried closer, will next time.
I have never had a load shoot such a different speed than the data said though. Average 2870 fps. 24" barrel, cold (4 Celsius/39 American), 95% humidity, seated far from lands, 800 ft. elevation. I guess it all adds up, but over 200 fps?? Does this sound right? Has anyone had this kind of a variance from a published load? The node was really nice and small, 19fps variance max across 9 shots, plus one outlier. Its got me motivated to tune this load.

Whenever I go to the range to do load development, I'll fire some known factory ammo or other previously measured ammo to get a baseline on my chrono for the day. I've had days where my chrono was just off for whatever reason that day and the factory ammo was a clear indicator.