Confusing Ladder Test Results

[baker1816]

Attempted to run a ladder test for my Rem 700 5R Mil Spec using SMK 175's. Got some very confusing results and was wondering if anyone has had something similar happen. I only shot one ladder due to unexpected storm hammering us so I had to leave. Here's the results of powder charge and velocity.

Varget powder
CCI BR2 primers
175 SMK bullets
Winchester brass neck sized & shoulder bumped .002"
Length - COL 2.805 / Ogive 2.225

43.2g 2661 fps
43.5g 2574 fps
43.8g 2656 fps
44.1g 2614 fps
44.4g 2569 fps
44.7g 2564 fps
45.0g 2569 fps
45.3g 2554 fps

I would like to think I was overly anal about my reloading procedures and measurements so everything was "perfect" as I could make it.

This was also after 40 rounds shot running another test with 168 SMKs that ran perfectly.

What are your thoughts? What am I missing? What could have gone wrong???

TIA for the input.

 

[dmoran]

Fouled out barrel... as a possibility.
Donovan

 

[baker1816]

Fouled out barrel... as a possibility.
Donovan

I hope not. I cleaned it before the range day and shot 45 rounds prior to the ladder test. I have a total of 170 rounds on the barrel.

 

[dmoran]

........shot 45 rounds prior to the ladder test......

Was the prior 45 rounds with the same powder/primer?
(mixed powder fouling can aggresively cause a fouled out barrel, is why asking)
45-rounds can be a lot of fouling - IME
Donovan

 

[boltfluter]

Looks like you labeled your ammo backwards. Based on the chrono numbers.

Paul

www.boltfluting.com

 

[baker1816]

Was the prior 45 rounds with the same powder/primer?
(mixed powder fouling cause a fouled out, is why asking)
45-rounds can be a lot of fouling - IME
Donovan

Everything was the same except bullets. The first rounds were 168 SMKs. The ladder test was with 175 SMKs.

 

[baker1816]

Looks like you labeled your ammo backwards. Based on the chrono numbers.

Paul

www.boltfluting.com

That came to my mind first too, but not the case. I loaded three rounds of a given charge. When that charge was complete, I colored the tip a specific color with a Sharpie, recorded the color and charge on a note card, and moved on to the next charge.

 

[boltfluter]

Just a thought. Scratching my head on this one. Can't really see lighting conditions effecting a chrono so uniformly. Assuming your chrono has sky screens. You got me on this one. Lol.

Paul

www.boltfluting.com

 

[Lapua40X]

If you pull the velocity numbers apart and re-arrange them in linear sequence to correspond with the linear arrangement of the load data the results reflect what I'd expect in a normal rate of increase in FPS per grain of powder. The only surprise in my review is the 2569 fps for 44.4g and 45.0g with the dip between the two or, when in linear sequence, the duplicated velocity in the corresponding .3 grain load change.
All I can suggest is that you clean the heck out of that rifle and have another go at it.

 

[Langey]

Will a graph help?

 

[L.Sherm]

I have saw this a couple times with rifles no matter how much powder you added no velocity change just didn't seem to like that particular powder so I switched and problem solved. Just a thought.

 

[Hoosier]

If all the ambient variables are constant, temp, pressure, and etc...the three things that could impact to differences are the primers, powder, and chronograph. My I ask what type of powder scale are you using? I have had fluorescent lighting effect my electronic scale.

 

[Hoosier]

Sorry, I forgot...are the batteries fresh in the chronograph?

 

[dcali]

I would question the chronograph. What kind is it? There should be a fairly obvious linear(ish) relationship between charge weight and velocity. Your numbers are going backwards. Did you shoot the rounds in reverse order?

 

[dmoran]

^^^ Nice chart....
Reversed data does look to be a strong potential culprit.
Donovan

 

[baker1816]

Just a thought. Scratching my head on this one. Can't really see lighting conditions effecting a chrono so uniformly. Assuming your chrono has sky screens. You got me on this one. Lol.

Paul

www.boltfluting.com

Yep, had sky screens on as well. I'm wondering if my chrono battery is getting low.

 

[baker1816]

If all the ambient variables are constant, temp, pressure, and etc...the three things that could impact to differences are the primers, powder, and chronograph. My I ask what type of powder scale are you using? I have had fluorescent lighting effect my electronic scale.

I use a Gem Pro 250 backed by a beam scale. I check each load with weights.

 

[baker1816]

I would question the chronograph. What kind is it? There should be a fairly obvious linear(ish) relationship between charge weight and velocity. Your numbers are going backwards. Did you shoot the rounds in reverse order?
View attachment 982766

I'm using a CEI Pro Chrono with screens.

 

[baker1816]

Holding for elevation and ignoring windage, the 300yd target max spread was 1.703" which is much lower than I saw with the 168 SMKs and tighter than I expected with 175 SMKs. I guess I'll run the other two ladders and see what happens. Thanks to all for the input and your time. I appreciate it!

 

[/VH]

I'm not a .308 shooter but I'm wondering if maybe Varget might be a little fast for 175 gn. bullets.