velocity or grouping with a ladder test

[haftime]

Rookie's 1st ladder test. I have .8 grains difference over 4 consecutive loads that yield a difference of 5 fps extreme spread but they don't group. 3 of the 4 are vertical and 4th (highest charge of the 4) is way off. The 2 closest shots (touching) were the 1st and the 11th (book max load). Follow up with the group or the velocity?

 

[Dmagna]

Depends on how the shots were taken, if you shoot with a magneto speed on the barrel then POI means nothing.

most of the time when you find a node then you reshoot that .8 grains with an ocw test then do a seating depth test to tighted the group up.

 

[GLTaylor]

For me personally, accuracy always trumps velocity.

 

[Quintus]

That is a wide node. I would load it again with 2 rounds in each charge. Shoot it one more time over the Magneto and then shoot it again without for group. Are you shooting new or fired brass?

 

[haftime]

Once fired and annealed. Not great brass but all I could get my hands on for now. Nothing attached to the barrel. I was surprised there wasn't much velocity difference. Think I will take your advice and retest those 4 loads and load #11.

 

[L.Sherm]

My ladder tests are all about point of impact i dont even use a chrono.

 

[QuietTexan]

Find velocity flat spot, then look at vertical. If it's bad, change powder. If vertical is good, you can try to shape the horizontal with seating depth. Could also start swapping primers to see if that tightens up the overall group in the velocity node.

 

[BrentM]

So you have 5 fps es over a .8 ladder. That's weird and makes me wonder about your chrono.

In this case, I'd reshoot the ladder with 2-3 rounds, probably 3, in .2 grains and see if things line up. Clearly, based on first test being accurate, you are in a wide velocity node.

There are lots of ways to get the end result a person wants but velocity ladders are absolutely one of the best ways to develop loads and exactly how I do it. Ladder with labradar or magneto, and find the upper node. Hone in on the middle are of the upper node looking for low SD and accuracy. Usually in the node, you will find a .2-.3 variance yields similar results of low sd and acceptable accuracy.

 

[aschler]

Rookie's 1st ladder test. I have .8 grains difference over 4 consecutive loads that yield a difference of 5 fps extreme spread but they don't group. 3 of the 4 are vertical and 4th (highest charge of the 4) is way off. The 2 closest shots (touching) were the 1st and the 11th (book max load). Follow up with the group or the velocity?

As many others have said, shooting more rounds at each charge weight is better. Also, you don't need to shoot the same amounts of shots for all weights, 1 round for the lower weights is fine and step it up to 2 or 3 as you get in the area you expect will be good. The reliability of the data you get will outweigh the cost of the extra rounds. Also, I don't shot at paper when I'm testing for velocity; I was tempted to go with a good group instead of what the velocity test was telling me and in the long run it always ended up being a waste.

 

[BrentM]

As many others have said, shooting more rounds at each charge weight is better. Also, you don't need to shoot the same amounts of shots for all weights, 1 round for the lower weights is fine and step it up to 2 or 3 as you get in the area you expect will be good. The reliability of the data you get will outweigh the cost of the extra rounds. Also, I don't shot at paper when I'm testing for velocity; I was tempted to go with a good group instead of what the velocity test was telling me and in the long run it always ended up being a waste.

Why not do both? Just curious. Good advice tho.

I shoot groups and velocity at 400-500. That range usually reveals a little more info to me. For example 60.2 vs 60.4 might both yield a good sd but the .2 might yield a exceptional accuracy group. If so, I usually call it good and just confirm the data. I don't waste my time anymore trying to get .1 more accuracy or 2 fps better sd.

 

[JTB]

I ran this ladder last week on a new 25 CM PRS build I just finished. There was a L to R wind as there almost always is here this time of year. It was shot at 300 yards so the separation could have been better at a longer distances. That being said you can still see the velocity vs vertical grouping and how they seem to correspond. I use a labradar chronograph

 

[BrentM]

I ran this ladder last week on a new 25 CM PRS build I just finished. There was a L to R wind as there almost always is here this time of year. It was shot at 300 yards so the separation could have been better at a longer distances. That being said you can still see the velocity vs vertical grouping and how they seem to correspond. I use a labradar chronograph View attachment 272542

And that 44.4 load looks to be money if it's the upper node and just below max. 4 ES at this point.

I personally have done the velocity and paper ladder for several years now. Without the paper you still the velocity node but now you have a new aim point and idea of where those impact. Me, I'd run another test on that 44.4 at 500 with my labradar and confirm data. I'd also make sure 44.4 isn't too narrow or between nodes. Run 42.3 to 44.5 for a check.

 

[aschler]

Why not do both? Just curious. Good advice tho.

I shoot groups and velocity at 400-500. That range usually reveals a little more info to me. For example 60.2 vs 60.4 might both yield a good sd but the .2 might yield a exceptional accuracy group. If so, I usually call it good and just confirm the data. I don't waste my time anymore trying to get .1 more accuracy or 2 fps better sd.

First, I can shoot a ladder off the back porch and am going to spent at least 1.5 hour to shoot groups. If I could shoot a decent distance right next to the house, I would probably try shooting groups to see if it was worth the additional hassle of shooting targets. Also, I'm looking for good SD and a wide flat spot when charting powder weight vs velocity. In your example, I would use 60.3 without even checking groups for 60.2 or 60.4 unless 60.0 or 60.6 also give good SDs and comparable velocities. I do this because it seems likes picking a value between 25% and 75% of the flat spot range gives you a consistent recipe even though it may not give you the best groups on a particular day. I've been burned before pursuing finicky loads because they showed a good group in a ladder so I try to do everything reasonable I can to stay away from them. I know if the rifle shoots .75 MOA, it isn't the limiting factor in my hands and I can usually get .5 MOA pretty easily with this method so that is what I use.

If shooting groups @ distance was convenient and I changed out my magnetospeed to a option not clamped to my barrel and I had a ladder of three consecutive charges with consistent velocities and the middle group had good SD and tight group, I would go with the middle group and call it a day. Right now for me, shooting for groups during a ladder test isn't worth the extra effort.

 

[BrentM]

First, I can shoot a ladder off the back porch and am going to spent at least 1.5 hour to shoot groups. If I could shoot a decent distance right next to the house, I would probably try shooting groups to see if it was worth the additional hassle of shooting targets. Also, I'm looking for good SD and a wide flat spot when charting powder weight vs velocity. In your example, I would use 60.3 without even checking groups for 60.2 or 60.4 unless 60.0 or 60.6 also give good SDs and comparable velocities. I do this because it seems likes picking a value between 25% and 75% of the flat spot range gives you a consistent recipe even though it may not give you the best groups on a particular day. I've been burned before pursuing finicky loads because they showed a good group in a ladder so I try to do everything reasonable I can to stay away from them. I know if the rifle shoots .75 MOA, it isn't the limiting factor in my hands and I can usually get .5 MOA pretty easily with this method so that is what I use.

If shooting groups @ distance was convenient and I changed out my magnetospeed to a option not clamped to my barrel and I had a ladder of three consecutive charges with consistent velocities and the middle group had good SD and tight group, I would go with the middle group and call it a day. Right now for me, shooting for groups during a ladder test isn't worth the extra effort.

Look at the wiser mount for the magneto. I have one, modified it, and it works well. I prefer my labradar, but the wiser is pretty cool.