Ladder test interpretation

[golfer]

I went and shot a ladder test yesterday. Just wanted to see what others thoughts were of the results I got. I’m confused by the velocities I recorded as they didn’t really seem to increase with increased powder charges and kinda just were all over the place. I was using a Labradar, but wonder if the ambient temperature may have had an effect on velocity readings? It was 7-8 degrees out plus wind. Just trying to gauge where to go next or what charges to focus on. I didn’t seem to see any sort of pressure and or hard bolt lift. Do I focus on the charges of 75.1-75.4 since it seems to be a bit of a flat spot or do I focus on shots 9,10,11 because they grouped together on the target?

 

[ismith]

Maybe I did the ladder test wrong, but I loaded 10 rounds per powder charge at 1/2 grain intervals from starting load to max load. I cooled the barrel between shots and ran a bore snake though the bore after shooting 5 shots.

 

[elkantlers]

Maybe I did the ladder test wrong, but I loaded 10 rounds per powder charge at 1/2 grain intervals from starting load to max load. I cooled the barrel between shots and ran a bore snake though the bore after shooting 5 shots.

You need to do something like this. 1 round per charge isn't going to tell you much other velocity increase over your 3 grains,

 

[elevatorman]

If it was me, I'd call it good and load up 10 more to go shoot another time, or load em all up, at 76 grains. Why not? Your showing great accuracy and have best velocity. Or you could always repeat the ladder test with say 3 at each charge weight starting at like 8 through 11 again. I guess it depends on what your trying to do. My rifle once I found a good load that got good velocity and less than 1 moa, I called it good and loaded em all up.

 

[Sheltowee]

@ismith and @elkantlers are right-- one round at each rung on the ladder isn't going to tell you much. Even when I'm loading strictly to find pressure, I load 3-5 cartridges per dose of powder. Ten rounds per rung will also give you a rough idea of SD/ES (although they're too small a sample to really be statistically significant, but I'm not trying to blast 8lbs of powder just to satisfy my college stats professor).

You might be getting some funky behavior because of the temp, as well.

 

[Potsie]

I’d load up 20 at 75.4 (#9) and see how they group.

If it’s crap, back off another ~ .5 grain.

 

[golfer]

@ismith and @elkantlers are right-- one round at each rung on the ladder isn't going to tell you much. Even when I'm loading strictly to find pressure, I load 3-5 cartridges per dose of powder. Ten rounds per rung will also give you a rough idea of SD/ES (although they're too small a sample to really be statistically significant, but I'm not trying to blast 8lbs of powder just to satisfy my college stats professor).

You might be getting some funky behavior because of the temp, as well.

I figured I’d see some lower speeds due to temp. Of the two rifles I was playing around with loads, both were well under what others had achieved. For this particular bullet/powder combo the source I went off of was getting 3526fps with a 24” tube. I have a 26”. Maybe my barrel is slow? Never would have thought to see so much ping ponging going on as charges increased.

 

[Addicting]

I think you’re in the wrong powder. The pressure wave is all over the place. So that tells me you’re blasting powder out the end of the barrel in a fire ball.

You should see consistency in velocity increases if the powder is burning completely in the barrel.

Loading more with that erratic burn is a waste of time and energy.

 

[Sheltowee]

@Addicting makes a good point. Nosler doesn’t list Magnum for the 110 Accubond.

Temp sensitivity doesn't necessarily impact pressure in a linear way. Was also curious if some of those rounds may have sat in a hot chamber longer than others.

Also, what kind of case fill are you getting? That seems like a lot of powder for the 257Wby.

 

[ccc23454]

Nothing personal, I wouldn't trust any of that data. Try again slightly warmer day and let the rifle sit between shots (something aint right). I typically load my weatherbys during ladder at .5 or.6 per load step and I dont mind finding a heavy bolt to know limits. I also try and shot on reasonably close to hunting temps day. My vote start over if your truely want accuracy with speed

 

[golfer]

@Addicting makes a good point. Nosler doesn’t list Magnum for the 110 Accubond.

Temp sensitivity doesn't necessarily impact pressure in a linear way. Was also curious if some of those rounds may have sat in a hot chamber longer than others.

Also, what kind of case fill are you getting? That seems like a lot of powder for the 257Wby.

They were shot one at a time then shot 3 shots from different rifle, walked down range marked my impacts then shot another single. With it being 7-8 degrees out I’m gonna lean on the chamber wasn’t warm enough to be considered “hot”.

Not sure how to Calc case fill.

 

[LuketheDog]

You need to do something like this. 1 round per charge isn't going to tell you much other velocity increase over your 3 grains,

Yeah, last time I did one it was four rounds at each load, and I only picked that many because the ammo box had rows of 4, easy to keep track of what load I was on.