Quick Load question

Rockydoc

Well-Known Member
What to adjust in order to get predicted muzzle velocity to match actual velocity of test load.

I adjusted Shot Start Pressure down to 0 and predicted velocity was still higher than actual.

The load is for a 35 Remington, Lee C358-200 powder coated and gas checked, 39.2gr Varget, CCI 200 primer. WW case 50.88 gr H2O case volume.

Predicted MV. 2022fps. Actual 1998fps avg. 10 shots. Is that close enough to rely on predictions of changes in powder quantity or brand?

Rocky
 

Rockydoc

Well-Known Member
I also want to predict adjustments in powder quantity when I change to a different brass case with a different internal volume.

Internal volume of my cases:
W-W cases = 50.88 grains of water
Hornady cases = 51.7 grains of water
R-P cases = 51.3 grains of water

Are these significant differences in volume?
 

Ian

Notorious member
Welcome to powder coat. Even with SSIP at zero the algorithm is thrown off about 5-7% by powder coat. Keep SSIP at 1100 and most other things will be right.

Now, QL gives muzzle velocity. Where and how are you measuring it? Known good chronograph?

Some powders don't play nice with the predictions, but very few. Most are within 20 fps of my Magnetospeed once I factor powder weighting for PC bullets.

To answer your original question, the realistic thing to do to tune the data to the actual measured MV is adjust powder charge in QL.
 

BudHyett

Active Member
I also want to predict adjustments in powder quantity when I change to a different brass case with a different internal volume.

Internal volume of my cases:
W-W cases = 50.88 grains of water
Hornady cases = 51.7 grains of water
R-P cases = 51.3 grains of water

Are these significant differences in volume?
There is an old "rule" stating six grains of cartridge brass occupies the same volume as one grain of powder. The variances in brass and powder make this "rule" invalid. Different companies have their own formula for brass. Powders greatly vary in density such as Hodgdon Trail Boss versus W-W 231. This old time rule is no longer relevant.

The difference between the volumes in your case lots show little difference. I weighed cases many years ago and got similar results. My experimentation showed choosing one brand of brass and shooting it as a lot number until exhausted was the better choice. Annual annealing and outside neck turning kept the brass usable for long periods of time. The wall thickness was set at .015, any less resulted in case neck splits within five reloadings.
 

Rockydoc

Well-Known Member
Welcome to powder coat. Even with SSIP at zero the algorithm is thrown off about 5-7% by powder coat. Keep SSIP at 1100 and most other things will be right.

Now, QL gives muzzle velocity. Where and how are you measuring it? Known good chronograph?

Some powders don't play nice with the predictions, but very few. Most are within 20 fps of my Magnetospeed once I factor powder weighting for PC bullets.

To answer your original question, the realistic thing to do to tune the data to the actual measured MV is adjust powder charge in QL.
My chrono is LabRadar
 
  • Like
Reactions: Ian

Rockydoc

Well-Known Member
Welcome to powder coat. Even with SSIP at zero the algorithm is thrown off about 5-7% by powder coat. Keep SSIP at 1100 and most other things will be right.

Now, QL gives muzzle velocity. Where and how are you measuring it? Known good chronograph?

Some powders don't play nice with the predictions, but very few. Most are within 20 fps of my Magnetospeed once I factor powder weighting for PC bullets.

To answer your original question, the realistic thing to do to tune the data to the actual measured MV is adjust powder charge in QL.
I am trying to determine what velocity will result from a given powder charge. To do so I will need to do something different to tune QL .
 

popper

Well-Known Member
Predicted MV. 2022fps. Actual 1998fps avg. 10 shots.
What is ES on the crony? You are off by 24 fps. Doubt you will ever get it spot on. Computer guess vs measurement. Personally I'd go by ES of the crony.
 

Ian

Notorious member
I don't know why, but I read that as 2202 fps. Yes, 24 fps is damned close! It is phenomenal that a simple thermodynamic model with so few inputs and so many unknown variables can spit out info within 1% of results.
 

fiver

Well-Known Member
if i could get a reloading manual and my real world velocities within 20 fps i'd be exstatic, extactic, ecstatick, able to spell ecstatic too.

throwing a powder coated bullet in the mix and using a computer program not programmed for them and being that close says your on to something with your numbers.
 

Michael

Active Member. Uh/What
Yep, what everyone else said.

Re: case volume, how much overlap is there if you measured 10 of each brand, and how much variation is there within each brand? The lines might get a bit blurred.

I wouldn't mix case make for the sake of consistency, but unless one brand liked a different charge weight just because, I wouldn't give it a second thought unless excessive pressures were looming.