reading targets

[Roger_M]

Did some load devlopment on my 6br today shooting varget and 68g bullets. i understand that vertical is an indicator of consistency in velocity. and that one has to find the "pressure node" in a barrel. My results seem inconclusive to me.

vert in group at 100yds

31g=.183
31.5g=.319
32g=.385
32.5g=.215
33g=.267
33.5g=.200
34g=.302

the group moved aroud a bit too. Does that tell anything?
will get the targets scanned soon and posted

 

[Roger_M]

hope this works

 

[jb77]

Roger, I may be mistaken here but you maybe are trying to draw some conclusions using the wrong test. Typically you will find nodes that your barrel likes by running a ladder test.

Your point of impact is going to move around when using different charges of powder due to different harmonics imparted to the barrel, there are also recoil variances due to the bullet being in the bore for different times as the velocity is increased or decreased.

Judging from your targets it looks like you have an accurate rifle to work with.

 

[Roger_M]

anyone got a good article on ladder tests?

 

[janderson0]

Here is one:
http://www.lima-wiederladetechnik.de/Englisch/Laddertest.htm#Laddertest

Jim

With my little knowledge of the test your 31.5 and 32.0 grain loads hit the same point. I've usally seen the test done at longer distance to show the POI better.

 

[ReedG]

Hi Roger:

I usually do my own version of the "ladder test". I fire 3-shot groups with the powder,s) of choice, going from 1 grain below max to 1 grain over max in .5-gr. increments with the bullet seated at the lands. This can be done with several powders if you haven't already decided on the one to use.

I then take the load that shot the most concentric group,not necessarily the smallest), closest to round, and load sets of 3 with that powder charge at -.010, -.005, +.005, +.010, +.015,into the lands), and by then you will have found the load your barrel prefers. It may sound like a lot of shooting, but it's the most productive 30 rounds you'll ever fire.

Also, a general rule is "vertical needs more powder/jam" and "horizontal needs less powder/jam" but that's not infallible.

I've shot over 3,000 68-gr. Bergers through two 6BR benchrest barrels and my best load is always 34.0 or 34.2 Varget with the bullet .010 to .015 into the lands.

You will see definite movement of groups on the target from the different loads, as stated above, from the harmonics created in the barrel. Looks like you've got a shooter -- enjoy!

 

[Aussie_bob]

By the look of the first group i would be starting at 29grs or 28.5 and working from there.
I don`t use a ladder test i use a chronograph and when the SD is down in the single figures thats where i start doing .2gr changes then when you have the load just alter the seating depth in or out .005"then when you have the depth you may have to just tweak the load again but if you start .010" in then just work out.

 

[Hackberry]

I thought I was the only one who had figured out that not all barrels respond correctly to ladder testing. . .

Never say "never" and never, ever, say "always" in reloading. . . :thumb:

Sunset