Thread: Incremental load test anomalies

Ok you gurus..

How often if ever, do you find in developing an incremental load test (often called a ladder), that your fastest chronoed average fps is not your heaviest powder charge?

I'm as meticulous as I know how to be, weighing each charge individually on a well zeroed balance beam scale and trickling up.

Yesterday my 3 shot average was just over 150 fps more at 3 0.5gn steps below max charge..

Possibilities:
- I'm not as meticulous as I think I am
- there is something varying at the range I am not aware of
- my chrony chrono is off
- a little pixie is yanking my chain

I have found this over time with different calibres, powders, bullet weights and rifles.

I'm no expert.

So, what is happening please?

I think what you seeing it what folks look for.....the flat spot in velocity means everything wrung out you can get,any more is wasted..... personally i wont/dont use chronicgraph but if your fast load is accurate...and is as you say couple grains below maximum....embrace it and stick with it..... and pixies pinned by wings to target board is not as much fun as it may first appear to be,

Bahaa..that was fast Micky, yeah I did wonder if the law of diminishing returns applied. Cheers

Many many things.....
If using an optical chrono take the velocities with a grain of salt. The results are often consistent but rarely accurate. They are good for identifying ES(velocity spread for given charge weights) but average for accurate velocity readings.
Brass prep can effect it variable neck tension clean or carboned up brass plus many other variables.
It really depends how deep down the rabbit hole you want to go.
There are so many things that can all effect velocity and accuracy it really depends what your trying to achieve.

Originally Posted by dannyb

Many many things.....
If using an optical chrono take the velocities with a grain of salt. The results are often consistent but rarely accurate. They are good for identifying ES(velocity spread for given charge weights) but average for accurate velocity readings.
Brass prep can effect it variable neck tension clean or carboned up brass plus many other variables.
It really depends how deep down the rabbit hole you want to go.
There are so many things that can all effect velocity and accuracy it really depends what your trying to achieve.

Thks.

My top goal is accurate tight groups. I.e. having a clue where my bullet is going to strike at a given range

Second is sufficient down range energy to do the job. Or, the distance down range the projectile runs out if humane puff

For the most part the chrono could be dispensed with. Most of my shooting is under 200m. If I can print paper with a consistent group at 100m the rest is somewhat academic

However, I am interested in being able to make an effective killing shot beyond 200m. If I can establish a reasonably approximate fps then of course I can get and idea of bullet drop and bullet energy at different distances.

But, its still not a huge deal to me. If I'm uncertain at 350m I'll get closer.

I have a place I can set gongs up out to 500m. With a large piece of cardboard behind. That exercise is arguably more important than accurate chronographing.

Nevertheless I thought it a useful question to explore.
Cheers

Originally Posted by dannyb

Many many things.....
If using an optical chrono take the velocities with a grain of salt. The results are often consistent but rarely accurate. They are good for identifying ES(velocity spread for given charge weights) but average for accurate velocity readings.
Brass prep can effect it variable neck tension clean or carboned up brass plus many other variables.
It really depends how deep down the rabbit hole you want to go.
There are so many things that can all effect velocity and accuracy it really depends what your trying to achieve.

Thks.

My top goal is accurate tight groups. I.e. having a clue where my bullet is going to strike at a given range

Second is sufficient down range energy to do the job. Or, the distance down range the projectile runs out of humane puff

For the most part the chrono could be dispensed with. Most of my shooting is under 200m. If I can print paper with a consistent group at 100m the rest is somewhat academic

However, I am also interested in being able to make an effective killing shot beyond 200m. If I can establish a reasonably approximate fps then of course I can get an idea of bullet drop and bullet energy at different distances.

But, its still not a huge deal to me. If I'm uncertain at 350m I'll get closer.

I have a place I can set gongs up out to 500m. With a large piece of cardboard behind. That exercise is arguably more important than accurate chronographing.

Nevertheless I thought it a useful question to explore.
Cheers

Originally Posted by Jhon

Thks.

My top goal is accurate tight groups. I.e. having a clue where my bullet is going to strike at a given range

Second is sufficient down range energy to do the job. Or, the distance down range the projectile runs out of humane puff

For the most part the chrono could be dispensed with. Most of my shooting is under 200m. If I can print paper with a consistent group at 100m the rest is somewhat academic

However, I am also interested in being able to make an effective killing shot beyond 200m. If I can establish a reasonably approximate fps then of course I can get an idea of bullet drop and bullet energy at different distances.

But, its still not a huge deal to me. If I'm uncertain at 350m I'll get closer.

I have a place I can set gongs up out to 500m. With a large piece of cardboard behind. That exercise is arguably more important than accurate chronographing.

Nevertheless I thought it a useful question to explore.
Cheers

Find a stable es charge and providing it shoots good groups varify velocity by shooting at longer ranges and calculate velocity by using the drop.

Loads where the powder is starting to be compressed often show a reduction in velocity. I'm buggered if I know why though.

Sometimes brass can be the culprit, weight sorting can help as often the heavier cases can have a lower internal capacity creating higher pressure. Brass from different lots can have a similar effect as well, neck tension and thickness can have an affect as well.

Could just be your chronograph playing up when clouds go by or if the light is not quite at the right angle, mine is hopeless in the late afternoon.

These are things that can make you start pulling your hair out. Settle on a load and go and see what it does at longer range because that will be the best indicator of what it will do in the field. If you can get out and set up some gongs, say one at 300 and one at 500 and validate your load you'll be away laughing.

Originally Posted by Rated M for Magnum

Sometimes brass can be the culprit, weight sorting can help as often the heavier cases can have a lower internal capacity creating higher pressure. Brass from different lots can have a similar effect as well, neck tension and thickness can have an affect as well.

Could just be your chronograph playing up when clouds go by or if the light is not quite at the right angle, mine is hopeless in the late afternoon.

These are things that can make you start pulling your hair out. Settle on a load and go and see what it does at longer range because that will be the best indicator of what it will do in the field. If you can get out and set up some gongs, say one at 300 and one at 500 and validate your load you'll be away laughing.

I started typing up a post with all this and other variables but didn't want to bamboozle the O.P there are so many many things....every time i think i have my system down to a point I'm happy with my process something else crops up
My latest battle is trimming and getting consistent and even chamfering

Sometimes brass can be the culprit, weight sorting can help as often the heavier cases can have a lower internal capacity creating higher pressure. Brass from different lots can have a similar effect as well, neck tension and thickness can have an affect as well.

Could just be your chronograph playing up when clouds go by or if the light is not quite at the right angle, mine is hopeless in the late afternoon.

These are things that can make you start pulling your hair out. Settle on a load and go and see what it does at longer range because that will be the best indicator of what it will do in the field. If you can get out and set up some gongs, say one at 300 and one at 500 and validate your load you'll be away laughing.

stop overthinking it...you say 99% of shots will be under 200 yards...so only a very rare over 300yard effort...... find whats accurate and chuck the plurry chronicgraph away.....

From my own experience and reading up the results of some extensive trials it seems that with mild loads velocity will increase in predictable 'lock step' with an increase in powder charge. I find that with subsonic loads using fast powders charge weight predicts velocity. But with slower burn rate powders and charges getting up towards pressure, velocity can get unpredictable. Superformance has had me wondering what was wrong with velocity drops and jumps not consistent with the charge (dannyb might remember my phoning and asking what he thought I had done wrong). Because we often start our full house load ladders just a few grains below max it doesnt allow much room before we get into the 'did I make a mistake at the scales' zone.

Neck tension?

Originally Posted by Marty Henry

Loads where the powder is starting to be compressed often show a reduction in velocity. I'm buggered if I know why though.

It is the neck of the case there is only so much gas can flow through the neck of the case when the maximum flow rate is exceeded there is a bottle neck and the gas flow
can't flow fast enough and starts to swirl slowing down the gas and drops the velocity, I did some tests years ago and found as the powder charge went up the velocity
started to go backwards as much as 10fps for 0.5 grain increase .