Interesting ladder test results. Ideas?

[Nevrsummr]

Doing load development on a few rifles and got some interesting results. How should i interpret the bump in velocity followed by drop in velocity? As far as the ES being sporadic i am also baffled. Same reloading process in other rifles and im getting single digit ES. The last 3 shot group was the best group of the day, but seeing very faint ejector mark. All shots were taken at high temps. 90 degrees in the shade. Only fired 2 rounds and cycled rifles to allow cool down.

 

[Nevrsummr]

 

[Zen Archery]

Simply answer use 79gr.
Complicated answer with so many variables to measure if you have the time and effort - internal case variance, case fill capacity, powder crush, chronograph moodiness, case temperatures, etc....
It's not an innumerable amount of variables to measure its just time consuming.

 

[Taylorbok]

what kind of brass?
What made you choose that set to test? 3329-3341 is your second largest velocity spread.

 

[Longtine88]

If it were me I'd go ahead and play with the 79.0 to 79.2 range.

 

[243winxb]

Velocity drop is a sign of high pressure.
Slow burn rate powder, burns till bullet exits the muzzle. All the powder may not burn.

A HIGH pressure load will consume all the powder sooner. Pressure in the barrel is lower at time of bullet exit. The friction of bullet causes drag, reducing velocity.

 

[Nevrsummr]

what kind of brass?
What made you choose that set to test? 3329-3341 is your second largest velocity spread.

Nosler brass. From 79gr on i had ejector marks. Great point on the velocity spread. I just didnt have a flat spot under pressure so i aimed for something. Probably the wrong thing.

 

[Nevrsummr]

Velocity drop is a sign of high pressure.
Slow burn rate powder, burns till bullet exits the muzzle. All the powder may not burn.

A HIGH pressure load will consume all the powder sooner. Pressure in the barrel is lower at time of bullet exit. The friction of bullet causes drag, reducing velocity

Simply answer use 79gr.
Complicated answer with so many variables to measure if you have the time and effort - internal case variance, case fill capacity, powder crush, chronograph moodiness, case temperatures, etc....
It's not an innumerable amount of variables to measure its just time consuming.

Unfortunately 79 showed faint ejector marks. Question, shooting in 90 degree temps, 2400 ft elevation. Should that give me the highest pressure i will ever see?

Normal shooting conditions for this hunting rifle will always be 75 degrees or under and higher elevations.

 

[Nevrsummr]

If it were me I'd go ahead and play with the 79.0 to 79.2 range.

Ill load it up slightly hotter. Nosler brass is pretty soft and seems to show ejector marks early. I just really dont understand the 78.8 group jump in velocity. It was higher than previous results of 79.6. I was starting to see a stiff bolt at 79.6 though.

Chrony is a labradar and seems to work great

 

[ShtrRdy]

I'd also see how groups look around 79 grains.

 

[BountyHunter]

78.7-78.9 test those

 

[Nevrsummr]

78.7-78.9 test those

I did. Thats the 3 shot velocities

 

[Nevrsummr]

Thanks for all the input. I think i will try a couple seating depths at 78.9 and 79. Right now im at 20 thou jump. Think ill try 30 and 40 thou jump? Or is that too much adjustment?

 

[RockyMtnMT]

At 79.6 you started to notice a slight increase in bolt lift or bolt lift became difficult? What powder?