Load development and POI question

[rockable]

I was doing some load development on my .308 today. I recently installed a new Shilen varmint contour barrel on my Savage BVSS. Any way, I was shooting some different loads of Varget at 100 yds. in .5 gr increments over my Magnetospeed, searching for a node. All of a sudden with a new load, my POI moved up about about 3". Windage didn't change much. After adjusting my scope, the POI held roughly for the rest of the rounds. This is not the first time I've experienced this with .308. Is this common? Is it due to the vibration of the barrel changing? Is it worse with larger calibers? Inquiring minds want to know. Thanks for your input.

 

[Dusty Stevens]

you probably shouldnt be doing actual load development with a magnetospeed on the barrel. maybe you experienced a point at which your barrel broke in, maybe your rest got settled in finally, your scope or mounts shifted, your load hit a good node- could be a number of things

 

[rockable]

I was actually looking for a velocity node to work around and wasn't looking for tight groups, per se. I shot maybe 2 other loads before the POI just suddenly changed and stayed there. Stock wasn't loose, scope wasn't loose, nothing I could find explained it, unless something internal to the scope changed.

 

[Dusty Stevens]

I was actually looking for a velocity node to work around and wasn't looking for tight groups, per se. I shot maybe 2 other loads before the POI just suddenly changed and stayed there. Stock wasn't loose, scope wasn't loose, nothing I could find explained it, unless something internal to the scope changed.

scopes shift. more than people realize.

 

[Uthink Uknow]

A lot of things could have changed. Did you remove the action from the stock? Did you use a Savage Nut or have you eliminated the nut? Is the barrel tight? Is the scope tight and not moving? Did you remove the scope to change barrels? I don't like the Magneto being attached when you are trying to do anything except check for velocity. I think the Magneto changes the tune and the POI. Other than that, I don't know what the cause might be.

 

[Bart B.]

Any weight added to the muzzle end makes it heavier and lowers the muzzle axis vibration frequency. That moves bullet impact because the muzzle axis will point someplace else at bullet exit with the bullets same barrel time.

Magnetospeed instruction's don't mention that. There's a calculator on line that figures out what several ounces will change the bullets departure angle for a 308 Win barrel's profile. Their specs don't include weights.

 

[Big Mc]

I was doing some load development on my .308 today. I recently installed a new Shilen varmint contour barrel on my Savage BVSS. Any way, I was shooting some different loads of Varget at 100 yds. in .5 gr increments over my Magnetospeed, searching for a node. All of a sudden with a new load, my POI moved up about about 3". Windage didn't change much. After adjusting my scope, the POI held roughly for the rest of the rounds. This is not the first time I've experienced this with .308. Is this common? Is it due to the vibration of the barrel changing? Is it worse with larger calibers? Inquiring minds want to know. Thanks for your input.

Your new barrel may need more foulers to settle in . Just my two cents Tommy Mc

 

[DaveTooley]

When I have a new or unknown wildcat cartridge I start with a reduced powder charge. I'll increase the powder charge to get the pressures up to what I describe as a warm load. Impacts on the target always rise as velocity and pressure increase. Then the POI settles down at a specific pressure. You may have gone through this same process without knowing it. The wildcard is the Magnetospeed. I have one but I don't use it in load development. Pressure signs and the target tells me what I need to know. Then I get a velocity reading. A chrono can have you chasing your tail.

 

[rockable]

Thanks, guys. I will figure this out eventually.