Long neck question

[SRSA311]

http://i1214.photobucket.com/albums/cc489/SRSA311/P4280002.jpg?t=1398808412

Here is a picture from this past weekend.
308, 168 gr HPBTM
43.0 grains of Varget
Federal match primers
I had some really long cases and thought I would try a test.
Remington brass trimmed to...
5 of each @ 2.020, 2.025 and 2.030
I was wondering if the length would effect the fps due to more neck holding the bullet.
I KNOW THAT YOU SHOULD KEEP YOUR CASES TRIMMED TO SPECS.
I also know that they fit in my chamber with no pressure indicators.
If I loaded this picture right, you can see the chrono. results above.
fps did not very much at all.
What surprised me was how the group size shrank.
Would this be due to better support of the bullet?
Groups 1, 2 & 3 on the top.
SRSA311

 

[CyaN1de]

I also know that they fit in my chamber with no pressure indicators.

Once you pinch the neck in the throat area you won't have to worry about which case length shoots better as you will most likely be looking for a new action and possibly a few body parts from organ donors.

Over length cases will not show pressure slowly like powder charges, .001 longer than the chamber and you will have a ruptured case. I would stick to no longer than .010 over trim length strictly for safety sake.


Now, is the load a proven load in your rifle or was this all just powder charge testing? Without a baseline load to compare to you might just have lucked out on the 2nd and 3rd groups. Even a bad load can put all the bullets in the same hole, this is why load repeatability is key.