Input wanted on a ladder test

[DZelenka]

I did a ladder test with my 6.5 x 55 using the 130 Accubond and RL 22 in WW cases with 210M primers. The rifle began as a Ruger 77 but now wears a Schneider barrel and a Brown stock. This rifle is a sub 3/4 MOA shooter (sometimes WAY sub). The test was fired at 200 yards. The ladder started with 47.3 gr RL 22 and went up in 0.3 gr increments to 50.0. 50.0 is pretty clearly max. The bullets hit in a clockwise pattern until I reached shots 8, 9 and 10. I am thinking that is the node. What do you think? Here is a picture of the target.

 

[acloco]

Yes, there is some info there, but I am just not seeing the distinct pattern.

There is such a wide variation for a 200 yard group, that something else may be happening here. 2 1/2" verticle dispersin between shots 1/2/3.

4/5/6 only 1" verticle, but 2" horizontal.

#7 is up in the north 40 with #3.

8/9/10 are 1.2"ish x 1.2" ish as well.

Did you run these over a chronograph as well? Would be interested in seeing the numbers there.

On another note, not every barrel likes accubonds for some reason. Some will shoot half MOA, others in the 2 MOA range - but either will hold the same across distance. Weight sort and bearing length sort the bullets by chance?

 

[DZelenka]

This rifle likes the 120 Ballistic Tip over 45.5gr of IMR 4350 and the 140 Partition over 47.5gr of RL22. Both are running right at 2800 fps (the 120 is a touch faster).

The rifle has a #3 barrel so it is a bit on the light side.

I did not chronograph it. I did not weight sort bullets or brass.

The rifle did not behave like I would have expected. The first 8 shots hit in a clockwise pattern. The last 3 show the only real group which is .65 MOA.

We had a very calm morning and I was shooting from a concrete bench with a rest rear bag. 10x scope.

Shoot a few more between 49.4 and 50.0?

 

[rscott5028]

I would probably repeat the test once or twice more just to be sure that it's consistent.

A chrony would be very handy if you've got one available.

Otherwise, I tend to agree with your analysis based on this very small sample.

-- richard

 

[Mikecr]

If you haven't found best seating depth yet, I'd test for it with ~#4 load, and then re-run the ladder.

 

[DZelenka]

If you haven't found best seating depth yet, I'd test for it with ~#4 load, and then re-run the ladder.

Why #4?

 

[rscott5028]

Why #4?

I can't speak for Mikecr. But as acloco pointed out, 4-5-6 might be a node and 8-9-10 might be a node. But, it's really hard to say for sure when you're dealing with small samples.

And, it's not clear what role if any the wind or general accuracy played.

I like to stick orange dots on my target to give me several aim points and shoot 2 or perhaps 3 shots at each dot for each powder level and then compare the tightness of each group as well as the relative POI.

-- richard

 

[Mikecr]

#4 is just provides headroom for seating tests.

 

[DZelenka]

I can't speak for Mikecr. But as acloco pointed out, 4-5-6 might be a node and 8-9-10 might be a node. But, it's really hard to say for sure when you're dealing with small samples.

And, it's not clear what role if any the wind or general accuracy played.

I like to stick orange dots on my target to give me several aim points and shoot 2 or perhaps 3 shots at each dot for each powder level and then compare the tightness of each group as well as the relative POI.

-- richard

Wind was negligible at the time this was shot. The general accuracy of the rifle is good for a sporter but any load that shoots better than 3/4 MOA is a contender. Most "good" loads for the gun will break 1/2 MOA with regularity but sometimes the groups are a bit bigger.

The only brass prep that I did was to uniform the primer pockets, chamfer the flash holes and trim the length. I did not weight sort the brass which is WW.

I use the ladder test to find a ballpark for more detailed load testing. It is not an end in itself. #5 and #9 may be areas to do that.

The seating depth is the same (measured at ogive) as I use for the 120 BT and 140 Partition loads.

Dan

 

[cdennyb]

I'd be curious of the bullet set-back from the lands as well.

Was it consistently within a few thou of being the same?
lightbulb
Some factory loads can be as far away as .030-040". My 300 win mag hates factory set-back and loves my .012-.015" set back. The difference is shooting a 1.5 MOA group of 10 or a .3-.5 MOA group of 10 just by the set back difference.

 

[DZelenka]

I'd be curious of the bullet set-back from the lands as well.

Was it consistently within a few thou of being the same?
lightbulb
Some factory loads can be as far away as .030-040". My 300 win mag hates factory set-back and loves my .012-.015" set back. The difference is shooting a 1.5 MOA group of 10 or a .3-.5 MOA group of 10 just by the set back difference.

I think these are .010" off. The reason I said "I think" is that I just used a precision mic to set it the same as my other Nosler loads that work. It is entirely possible that I could find these to be more or less than .010 off if I make the measurement using the 130 AB. I put these together on a whim last night since I was headed to the range today for other work.

Dan

PS It never ceases to amaze me that you can shoot a 1.5 MOA or so group using 10 different loads in a 2.7 gr range.

 

[rscott5028]

I think these are .010" off. The reason I said "I think" is that I just used a precision mic to set it the same as my other Nosler loads that work. It is entirely possible that I could find these to be more or less than .010 off if I make the measurement using the 130 AB. I put these together on a whim last night since I was headed to the range today for other work.

Dan

PS It never ceases to amaze me that you can shoot a 1.5 MOA or so group using 10 different loads in a 2.7 gr range.

Well, if you ever get caught in a survival situation, you know you can squeeze the neck with some pliers, shovel some powder in with a tea spoon, and tap a bullet in place with a block of wood and feel comfortable that you've got a 1.5 MOA load. gun)

 

[cdennyb]

There's really no reason to "think" they are close to the same, unless those two bullets have the exact same ogive, length, depth of seating, etc. then they more than likely are not.
Properly measuring the round for the COAL number in the worst case scenario (use any of a several methods) you intend to load is the only way.
Just a thought on my part, I'm sure you're no beginner from what you've asked and what you've related to us.

 

[DZelenka]

Well, if you ever get caught in a survival situation, you know you can squeeze the neck with some pliers, shovel some powder in with a tea spoon, and tap a bullet in place with a block of wood and feel comfortable that you've got a 1.5 MOA load. gun)

I think I can dig around and come up with something a bit better than that.