Quickload question

[spawndn72]

I received my copy of quickload yesterday, so I am very new to the program.
I entered in everything for my 250 grain missouri bullets cowboy #1 45 colt load using 7.1 grains of Unique.

Quickload estimates a velocity of 842fps out of my 5.5" barrel. My shooting chrony shows a mean of 655 for 5 shots. Lowest was 622, highest was 686. My Dillon powder measure was throwing anywhere from 7.1 to 7.3 grains which would account for the spread in velocity.

Any idea what might be causing this?

 

[mcb]

Double check the case volume of the brass you are using matches what is in QL and that your bullet parameter match your actually bullet and that your seating depth is correct.

Measure the cylinder gap of your revolver. If it's more open than 0.003-0.006 you might be loosing some extra velocity there that quick loads cannot account for.

I threw some numbers in my copy and can't match your actual velocity either. I increased case volume slightly, turned down Shot Start Pressure to 500 psi, and still only get down to ~780 fps. I probably don't have the same bullet parameter entered since I don't have the length of that bullet.

I have found Quickloads can sometimes struggle with lower pressure/velocity loads.

Sorry not much help

 

[spawndn72]

I checked everything you told me to check. Bullet length and seat depth is correct. Case capacity is right. Cylinder gap is 0.0035. Below is a screen shot

 

[higgite]

I believe what mcb was referring to is the actual case capacity of your brass, not whether you chose the correct case in QL or not. Your screen shot shows the QL default case capacity for .45 Colt (SAAMI) which is probably different than the actual capacity of your sized brass. For QL to accurately reflect your real life conditions, you need to measure the case capacity of your brass and input that into the "Maximum Case Capacity, overflow" slot. Also, for bullet, case and cartridge lengths, are you using your actual measurements or the QL defaults for that caliber?

 

[243winxb]

Quickload estimates a velocity of 842fps out of my 5.5" barrel. My shooting chrony shows a mean of 655 for 5 shots.

From my readings on the internet-

More common with hand gun ammo. Even the rifle guys adjust data input so QL matches their recorded velocities.

It may all be a problem with the learning curve? But may be more the components used.

A gov test on IMR 4831 showed the difference between the fastest and slowest lots. This made a huge difference in velocity and pressures.

After reading this, https://www.accurateshooter.com/gear-reviews/test-quickload-review/ i decided i dont need or want one. It made my head hurt.

But would be a fun toy, just seeing how pressure is affected by 1 change at a time.

 

[spawndn72]

I believe what mcb was referring to is the actual case capacity of your brass, not whether you chose the correct case in QL or not. Your screen shot shows the QL default case capacity for .45 Colt (SAAMI) which is probably different than the actual capacity of your sized brass. For QL to accurately reflect your real life conditions, you need to measure the case capacity of your brass and input that into the "Maximum Case Capacity, overflow" slot. Also, for bullet, case and cartridge lengths, are you using your actual measurements or the QL defaults for that caliber?

The default case capacity actually matched my measured case capacity and I used actual measurements of the bullets and the brass.. I also adjusted the case capacity variable up and down by several grains and while it made a difference, it did not make a 200fps difference, more like 20-40fps difference.

After thinking about this some more, I think that quickload does not take into account the cylinder gap and I think I am getting excessive blow by due to the brass not expanding since it is such a low pressure charge.

 

[unclenunzie]

I don't know if this helps - but with my 5.5" barrel Cattleman using 8.0 grains Unique at 1.6" OAL, laser cast keith 255gr:

2, 5 shot strings ProChrono: (hi 816 lo 771 av 793 es 45 sd 18) (hi 801 lo 772 av 787 es 29 sd 10)

I am a novice at this but I wonder if your powder charge is giving you about what you could expect. Using mostly defaults in QL it says 906 fps for this load, knowing my input data is not perfect (I attempted to give it calipered bullet data). It puts this charge's max pressure right under 14000 PSI.

 

[mcb]

The default case capacity actually matched my measured case capacity and I used actual measurements of the bullets and the brass.. I also adjusted the case capacity variable up and down by several grains and while it made a difference, it did not make a 200fps difference, more like 20-40fps difference.

After thinking about this some more, I think that quickload does not take into account the cylinder gap and I think I am getting excessive blow by due to the brass not expanding since it is such a low pressure charge.

Cylinder gap and case seal are definitely factors that Quick-loads does not capture.

Also at these low pressures the powder is not burning as efficiently as it would at higher pressures so some of the parameters related to the propellant (ie heat of explosion, progressive burn limit, etc) might be effectively too high for these conditions. But I typically don't mess with those parameters in my use of Quickloads. That is getting into aspect I have a decent understanding of but insufficient information to change with anyway to validate my changes given what little real world data I can collect (basically muzzle velocity).

If you want to dabble in there, unlock the propellant parameters and lower the heat of explosion by a few percent at a time and see if you can get it to match your chrono data without making too big of a change. This is basically saying that due to the lower pressure your not efficiently converting all the chemical potential energy to useful work. I would not mess with the other parameters other than for curiosity's sake.

If you have the stomach for some gritty thermodynamics read the technical background information that comes with Quickloads. It is really thermodynamics heavy but it really does layout everything the program is simulating fairly well and would give you more intuition into what all the parameters including the propellant parameters mean. It should be in the install directory or on the disk somewhere.