3 shot group vs ladder tests

[Fuj]

leave your chrono at home....paper NEVER lies !!

I like to argue this statement.....If you have the eguipment, use it.
Mines on the bench every session during development. I fire no
less then 3 shots in any test string. When firing a test group with
two in the same hole and one way out, the chrono will tell you if
you screwed up a charge making that test group skewed. A shot
going out of a group can be caused by many things, but the chrono
will tell you if velocity was part of the problem. Then again, had a
2830, 2842 and a 2790 that shot a two......If that 2790 would have been
closer to the first two, would it have been a 0ne ?? Smoke em' if you
got em'.......

 

[Doom]

I like to argue this statement.....If you have the eguipment, use it.
Mines on the bench every session during development. I fire no
less then 3 shots in any test string. When firing a test group with
two in the same hole and one way out, the chrono will tell you if
you screwed up a charge making that test group skewed. A shot
going out of a group can be caused by many things, but the chrono
will tell you if velocity was part of the problem. Then again, had a
2830, 2842 and a 2790 that shot a two......If that 2790 would have been
closer to the first two, would it have been a 0ne ?? Smoke em' if you
got em'.......

Ok, I'll bite! While your point is actually valid the issue is the chronograph data is only ONE element of precision and its importance is related to the time of flight (distance) that the bullet travels. The effect of a 20 or even 50 fps variation in velocity on 100yd test is noise. The effect is less than one caliber for most centerfire cartridges. Correlation to the point of impact is lost in the myriad of other effects. Depending on the barrel characteristics at the point of release a lower velocity bullet may actually impact higher that the higher impact bullet.

Bottom line is the velocity data is good imformation to have. Ultimately it is important but only within the context of the rounds consistency or other requirements, such as power factor. The first requirement for precision (my order) is that the barrel is pointed in the same line of sight for each round with small changes in velocity/barrel time and minimal cross velocity. Determining that load/"node" doesn't require specific knowledge of velocity. Unfortunately too many people think of chronograph data as an "Easy Button" and an end all to load development. Even experienced shooter fall into this trap. Scott Satterlee proposed his 10 shot velocity ladder test based on some data that he saw (flatter spots) for different charge weights. Unfortunately he misinterpreted the cause of the flat spots.

 

[Rope2horns]

Let me guess, We should also tune at 100 yards and not chase the lands? LOL

Now you're just giving away all the secrets.

 

[KMW 1954]

My perspective; I am a novice target shooter, I am not shooting top of the line equipment, I shoot from a bench with a bipod and a bag because that is what our league dictates. I am also only shooting short range out to 300yds.

First an foremost I need to be honest in the assessment of my own abilities and capabilities. Next I need to remember my equipment short comings. After-all the rifle and the ammunition's are only going to perform to my ability. I can consistently shoot .5MOA and when on a good day I can shoot .2MOA. Then on those somewhat rare occasions I can put 2 rounds into the same hole. But yes I believe this rifle and ammunition is much more accurate than me.

Now with time and experience I am learning to call those errant shots more and more. So for me it is taking more than just one 3 shot group to determine a good, reliable and repeatable load. I test fire to find a consistent group. One I find what I believe is the most consisten group I will load it several more times and shoot it on alternate days and times to try and validate it.

This may not be the best method or the most economical method but for me it works and also provides valuable trigger time to work on my mechanics and posture. I don't want to argue Why, I just want to see acceptable results. I also feel my skills and abilities are slowly catching up to my equipment.

 

[urbanrifleman]

I recommend running your “ladders” with three shot groups. Single shot ladders can be especially misleading. Two shot ladders may tell you what a barrel doesn’t like, but they won’t necessarily tell you what a barrel likes. You get more information about grouping, flat spots as well as how each of the charges “moves” shooting three shot “ladders”.

Remember, you aren’t looking for different charges that produce the same velocity. You are looking for points where the barrel harmonics and the velocity dump different charges into the same group(elevation).

Here is an old 1K three shot AA2495 ladder I shot when H4895 was in short supply. Two nodes were identified for this BRA barrel. Next step was a three shot test with a finer 1/10th grain increment. Sorry about the joke Roy!

View attachment 1674550

Things get tougher at 600 yards because shots start to cluster closer together, hopefully. Here is an old 600 yard ladder again with a BRA. Shortly after shooting this, the barrel, with 29.7 gr., shot the smallest 8 target aggregate ever shot at IBS Nationals. It was 1.611”

Notice the overlap of 29.7, 29.8 and 29.9. I like it when a lighter load prints on top of or preferably slightly higher than a heavier load. I will pick it every time. Sorry shot marker guys, but you really need a piece of paper in your hand to let it talk to you. It’s all about those triangles!

View attachment 1674551

Here is a seating “ladder”. I had a proven load with this 6.5x47L but was concerned about throat movement firing a 16 target match. The left to right wind kept picking up as I shot but you can see that .006” jump all the way up to .018” shot at about the same elevation so I had .012” of erosion to play with.

View attachment 1674553

This barrel and load ended up shooting a tiny 1.338” group at the Rendezvous three weeks later. The bottom line is three shot group “ladders” help me develop sound loads while minimizing round count. I then verify with 5 or ten shot groups depending on the match I’m tuning for.

View attachment 1674579

Dave.

That 2880 node in the 6bra is hard to beat.

 

[Bc'z]

That 2880 node in the 6bra is hard to beat.

Considering that where my 6br is shooting I'd have to agree. Lol

 

[JFrank]

Some times it is and sometimes it ain’t ‘ you shoot the one that shoots best.
I can’t say I’m going to shoot a 2880 node because it might not be there when I run a ladder.

 

[Steve Donlon]

Some times it is and sometimes it ain’t ‘ you shoot the one that shoots best.
I can’t say I’m going to shoot a 2880 node because it might not be there when I run a ladder.

You got to start some where.

 

[JFrank]

The point I’m making is that powders lots are not all the same, I chase the tune not the speed.
I have a lot of N140 that shoots well at about 2880, Varget tuned in about 2930 and some H4895 that shoots lights out at around 3000 so if I tried to focus on speed I’d be in trouble. I’ve done that before about five years ago and it doesn’t work very well.