Help with tune

[Link]

I go out and shoot this ladder and think I have found a good node at 30.6 of h4895 so I go out and shoot a group of 4 and it's not so good [# 1 group]. I shot groups of 4 because I used the 5th one to run over my Magnatospeed. Then I shoot a group of 4 at 31.2 being 31.0 and 31.2 were so close together, just to see if there is a node there.[# 2 group ]. The group was good
I chronographed 31.2 at 2967fps,
30.6. at 2937fps.
31.2 at 2967fps
31.4 at 3012fps. And
31.6 at 3004fps with no signs of pressure.
Now from what I gather my node didn't work out the way I thought? When I jumped from 31.4 to 31.6 I lost velocity? Maybe a magnetospeed error?
Looking to learn as always

 

[Link]

More info 6brI, 1X8T, 200+ rounds breakin, 105 VLDs 300 yd ladder, 100 yd target.

 

[urbanrifleman]

31.4 is probably the flat spot on the curve.

 

[Terry]

A drop in the speed, or no increase is a good thing. It's usually the sign of an accuracy node.

Watching with interest.

 

[urbanrifleman]

I think you should find the optimum seating depth first before you do a velocity ladder or node search. You really don't know if you are in tune if you haven't.

 

[Terry]

I think you should find the optimum seating depth first before you do a velocity ladder or node search. You really don't know if you are in tune if you haven't.

Interesting

I have never done it that way.

Watching with interest.

 

[urbanrifleman]

Interesting

I have never done it that way.

Watching with interest.

There is an optimum seating depth that will shoot best at ALL powder charges. And while you can be in tune at a less than optimum charge the tune window will be unstable and very narrow. From my testing the seating depth has larger effect than the powder charge.

 

[urbanrifleman]

Here is an example of seating depth and charge at the same time. Charge is across from left to right, and seating depth is shown in the rows across going down. You can see the groups getting smaller and more consistent as the bullet approaches touching. The top row is 20 in from touching. Each row going down is 4 thou shorter. The bottom row is 4 thou in.

 

[Link]

I did a seating depth test as Burger suggests there were 2 about the same results 2.650'' jump and 2.750'' a little in. Measured ogive to head. I went with 2.750, maybe I should go with the jump so I don't have to chase oal in the future.

 

[urbanrifleman]

Here is the continuation of that load development. As you can see the bullet shoots good alcross the weights of charge at that depth. I think it might shoot even better at 2 thou in. Need to get back out and finish. 100 yards.

 

[Curious]

There is an optimum seating depth that will shoot best at ALL powder charges. And while you can be in tune at a less than optimum charge the tune window will be unstable and very narrow. From my testing the seating depth has larger effect than the powder charge.

How do you pick a suitable powder charge to do your seating depth tune that ensures your not tuning a scatter node??

If you picked a charge that was on the edge of a node or even worse on a scatter you would not get very good results on the seating depth test?

 

[urbanrifleman]

How do you pick a suitable powder charge to do your seating depth tune that ensures your not tuning a scatter node??

If you picked a charge that was on the edge of a node or even worse on a scatter you would not get very good results on the seating depth test?

Just use a low charge. And no, it doesn't make a difference. The seating depth that is the best one will shoot the best not matter the charge.

 

[urbanrifleman]

If it were me I would do my seating test at 30.6 since you already found that to be the velocity dead spot. But seating depth is velocity, so after you find the seating depth you may have to tweak the charge to get back to the velocity sweet spot for the barrel. That is why it is best to do both at once.

 

[joshb]

Bump.

 

[Nick_Mansfield]

watching/curious

 

[SMK Shoe]

Watching