QuickLoad tuning question for QL users

[jebel]

I'm still learning how to tune QuickLoad and have a question about the Burning Rate Factor (Ba).

I have two loads, each of a different chambering (7mm-08 and .338-06). I'm using Varget in both of them, the same lot (same bottle). I have input the bullet dimensions, seating, and case capacity for each into QuickLoad. I have chronograph observations for each load (LabRadar), conducted around the same time and atmospheric conditions.

In the first load (7mm-08), QuickLoad is underestimating the observed velocity. By increasing the Burning Rate Factor by 7.8%, I can match my observed muzzle velocity (and I'm just over Max Average Pressure).

In the second load using the same powder, QuickLoad is overestimating the observed velocity. By decreasing the Burning Rate Factor by 2.3%, I can match my observed muzzle velocity (and pressure is ginger).

Question: (1) Is this weird? The impression I have gotten from reading QL user comments is that the Burning Rate Factor might need to be adjusted, as lot-to-lot variation exists, but you would expect that entire lot to be of a comparable rate. Or (2) is this normal, as one cannot compare burn rates between two different cartridges even using the same powder due to other factors? Or (3) is this an indication that I should be looking at other factors to tune in QuickLoad besides (or in addition to) the Burning Rate Factor? FYI, the weighting factor for both cartridges defaults to 0.5 and I left it unchanged.

 

[bigedp51]

The information I sent to you shows tweaking the burn rate and if needed tweaking the bullet weight very slightly.

And as long as the chronograph velocity matches the Quickload velocity it means the chamber pressure is a very close guesstimate to actual chamber pressure.

Just remember it is only a software program and it must be adjusted and tweaked for every firearm and the components used when reloading.

Example below
A brand new Savage button rifled barrel bore scope photo.

And below a custom hand lapped barrel.

Bottom line, Quickload doesn't know what type finish your barrel has or its actual bore dimensions. So you must adjust and tweak Quickload to get approximate answers.

The throat in my Savage .223 is longer than the throats in my AR15 rifles. And there are no adjustable throat variations in Quickload between .0250 and .0500. And my Savage throat length is .0566 so thats a lot of burn rate adjustment tweaking Quickload.

When I first bought Quickload I did not have a chronograph and was disappointed how far off the default settings were from the reloading manuals. And when I did get a chronograph I still didn't think much of Quickload and having to make adjustments to it to get close to the reloading manuals.

After this its more money buying a Pressure Trace System and getting more accurate pressure readings. BUT its the strength of your cases brass and construction that ultimately governs how hot you can load. And Quickload doesn't tell you that either and your Federal primer pockets will stretch out of shape sooner than other brands of brass.

Call me old fashioned but nothing beats making a workup load and reading the brass and primers for signs of pressure and also measuring base expansion just above the extractor groove.

 

[eklarsen]

You are doing it correctly. One other thing to double check is the seating depth of the bullet, if you have measured the h20 capacity, seating depth, OAL you need to adjust that burn factor and yes, the same powder can be different in a different case\caliber.