Range Report Quickload tweaking - some observations and ??

N

Notso

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Nov 28, 2010
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#1
So I finally sat down yesterday and played around with QL some more trying to get the output data to better track my chronograph results across several different load development efforts and now I find I have more questions than answers.

My starting assumptions: CED M2 chrono, Varget powder, 4 different bullet types (175/168 SMKs, 168 AMAX, and 185 Berger BTHPLR), and two different brass makes (Lapua and WIN). I have lots of chrono data for all of the above after doing ladder tests and I plugged them into an excel spreadsheet to then compare to QL. I meticulously measured the level water capacity of the brass per the QL instructions and then ran all my loads through QL to see what I got. QL was very close on some loads and just in the ballpark on others. Sometimes I was under 10 fps and other times the QL varied by up to 20-40 fps.

So I played with both the burn rate factor as well as the starting pressure. By manipulating one or the other, I could get a specific load to track one ladder test for a specific bullet and brass type. But as soon as I changed one or the other
(bullet or brass type) the QL results would no longer track.

I thought I would get the better results by playing with the burn rate factor (Ba) but I actually got closer with the starting peak pressure field. However, I think that field depends too much on the seating depth and is only going to work for one specific bullet and seating depth.

Anyway, sorry for the novel..... I'm starting to become disenchanted with QL. If it doesn't track real world data, what is the point? My understanding is it's designed to be a "predictive" tool. But I'm not sure I can trust it completely. Is it designed to just get you in the ballpark for truncating load development but you still have to do OCW or ladder tests to get the real answer?

So here are the specific questions:
1 - how do you guys use QL?
2. - how much tolerance or slop in MV is acceptable?
3 - how close do QL OBT numbers have to the OBT chart to be considered "on the node"?

Thanks in advance for any insight and help.
 
#2
Re: Quickload tweaking - some observations and ??

1. As a help tool and estimator and with observed data as a baseline. For me QL works great for N140 and for low-medium pressure loads while for N540 and high pressure loads it requires a bit of tweaking (case capacity, starting pressure). For me it underestimates loads - which is good as it's additional precautionary measure.

2. Depends, there are many factors involved (also Chrony accuracy - i found my Master measured very differently the same load in the sun and few seconds later when the cloud covered the sun).

3. I have a OBT node in QL for Tikka (23,75" barrel) at 1,350ms while by tables it should be around 1,300ms but still don't get too attached to the numbers it's just a approximation tool. I use it to get into the ballpark and work from there.
 
#4
Re: Quickload tweaking - some observations and ??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: TwoGun</div><div class="ubbcode-body">It's just a tool to get you in the ball park. Each barrel/chamber is cut differently so it's unlikely you'll get the same results across barrels, not to mention across lots of powder. If you really want to know what's going on, you'll need a strain gage setup.

http://www.shootingsoftware.com/pressure.htm</div></div>
Except that the strain gauge will only give you accurate pressure changes and can not give you an accurate actual pressure because you can not (inexpensively) get the actual pressure as test loads still are subject to "your" barrel, chamber, throat, etc.
I like QL it seems to work well and the more info you can supply it the more accurate it becomes. Once you get it down for a particular rifle you will be pretty dang close when changing one or more items.
 
#5
Re: Quickload tweaking - some observations and ??

These are QL-tweaking tips from another forum written by Chris Long. Chris is the father of the Optimum Barrel Time load development process, which is the entire reason I even have a chronograph, much less QuickLoad.

*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*

My three main "tweaks" in QL are:

1.) Burn rate - no more than 5% higher or lower. More than that and I go to #2
2.) Weighting factor - no more than 10% change from QL default, else go to #3
3.) Bullet weight - this is a very good way to compensate for bore friction and other physical things that QL can't model. An increase in friction effectively reduces the accelerating force on the bullet, slowing it down. Increasing the bullet mass does the same thing in QL (F=MA). If you have to tweak this by more than a few single digit percentages, then there is something very weird going on. If things get too weird, reset it all to QL defaults, and start over with just the bullet weight and see what you get. I had one Savage 6mm barrel on a friends rifle that was really rough, and required a 3 grain increase in bullet weight (from 105 grains) to get the velocities to match. It was the only tweak that would let the model even get close to the right predictions.

The process is trial-and-error, tweaking these parameters until you can match at least two velocity measurements. I usually fire at least three different charge weights, from low to high, trying to bracket the expected OBT velocity range(s), and record velocity for each trial. It is best to fire 5 shots at each weight, if you have the patience, as the velocity average will be much more accurate than a single shot value. Single shots are OK to get you in the ballpark, but to get a good QL model, you need more than 1 at each charge weight. Then, tweak QL until you get the best match to your data samples.

You will find that it is very difficult, if not impossible to get an exact match for some component combinations. I am convinced that there are non-linear effects in the actual powder burn process that QL's linear system models do not encompass. However, if you work at it, you should get the model to match well over the range of velocity that encompasses the OBT you are shooting for. If in doubt, try narrowing the test velocity range around the target OBT node, and try again. Once you get QL calibrated, you can adjust the charge weight in QL to hit an OBT on the nose. That will be your starting load for an OCW type test.
 
#6
Re: Quickload tweaking - some observations and ??

Fred C Dobbs beat me to the punch. About the only thing I can add is you must calibrate QL for each bullet/powder combination. I also tend to run a higher 'weighting factor' for heavy-for-caliber bullets.
And Chris says about +/- 20 micro seconds (.020 mS) is usually close enough.
 
#8
Re: Quickload tweaking - some observations and ??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: The Mechanic</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: TwoGun</div><div class="ubbcode-body">It's just a tool to get you in the ball park. Each barrel/chamber is cut differently so it's unlikely you'll get the same results across barrels, not to mention across lots of powder. If you really want to know what's going on, you'll need a strain gage setup.

http://www.shootingsoftware.com/pressure.htm</div></div>
Except that the strain gauge will only give you accurate pressure changes and can not give you an accurate actual pressure because you can not (inexpensively) get the actual pressure as test loads still are subject to "your" barrel, chamber, throat, etc.
I like QL it seems to work well and the more info you can supply it the more accurate it becomes. Once you get it down for a particular rifle you will be pretty dang close when changing one or more items. </div></div>

What are you saying? The strain gage is attached to the gun you are testing. If properly calibrated, a strain gage gives you the actual chamber pressure of the rifle it's attached too. I've witnessed the Oehler 43 in person and it tells you exactly what's going on assuming the strain gage is located and calibrated correctly. Not a difficult process and strain gages are not expensive. One can attach a gage to every bolt gun one owns. Obviously a chronograph is necessary to see the entire picture but I assumed that was obvious.
 
#9
Re: Quickload tweaking - some observations and ??

An external strain gauge can give you pretty accurate pressure gain and reduction readings but the calibration process is by its very nature flawed. Picture an inflated balloon that you can only measure the internal pressure with the expansion or contraction of the balloon. You can get pretty close but you don't really get the actual real pressure inside the balloon without measuring it internally. Just saying you can have a "calibration, test load" that you may think is "X" pressure but it may not be due to variables difficult to predict without a large amount of calculations like chamber size, throat, freebore, barrel roughness, yada yada yada.
 
#10
Re: Quickload tweaking - some observations and ??

SAAMI uses a hole in the test barrel right on the cartridge case to get their readings. Much more accurate but still this is from a SAAMI posting.
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Under SAAMI proof test procedures, for bottlenecked cases the center of the transducer is located .175 in (4.4 mm) behind the shoulder of the case for large diameter (.250 in (6.4 mm)) transducers and .150 in (3.8 mm) for small diameter (.194 in (4.9 mm)) transducers. For straight cases the center of the transducer is located one-half of the transducer diameter plus .005 in (0.13 mm) behind the base of the seated bullet. Small transducers are used when the case diameter at the point of measurement is less than .35 in (8.9 mm).

Under C.I.P. proof test standards a drilled case is used and the piezo measuring device (transducer) will be positioned at a distance of 25 mm (0.98 in) from the breech face when the length of the cartridge case permits that, including limits. When the length of the cartridge case is too short, pressure measurement will take place at a cartridge specific defined shorter distance from the breech face depending on the dimensions of the case.

The difference in the location of the pressure measurement gives different results than the C.I.P. standard.[11]</div></div>
A quick google got me this article that seems pretty interesting also.
http://firearmshistory.blogspot.com/2011/01/testing-firearms-measuring-chamber.html
 
#11
Re: Quickload tweaking - some observations and ??

I don't know how flawed it is if you have all the parameters calibrated (quality strain gage, proper application, proper placement, brass thickness, barrel thickness, etc.). Even SAAMI can be 3% off according to your article and CUP can be 5% off. A strain gage is the only thing that will even come close to telling you what's going on plus it has the advantage of indicating a secondary overpressure from the use of powder that is two slow for the cartridge. And it's way better than using Quikload to create a charge that isn't published. The Oehler is an outstanding product but the RSI is probably a good unit as well. Those combined with the other tools can do some interesting evaluation not possible by looking at primer flattening, ejector flow or a sticky bolt. Plus, it's not theoretical. The actual barrel, chamber, brass, bullet and seating depth in a given atmosphere are giving real measured results. Accurate or not, it's real data which is still better than anything published.

http://www.shootingsoftware.com/ftp/PTII-Help.pdf
 
#12
Re: Quickload tweaking - some observations and ??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: TwoGun</div><div class="ubbcode-body"><span style="font-weight: bold"><span style="color: #FF0000">Accurate or not</span></span>, it's real data which is still better than anything published.
</div></div>
Isn't that exactly what I said? Not at home but I can show you some .50 CBC pierced primers that you would swear is overpressure except it was a bad bunch of soft primers. I can show you some separated cases you would swear is overpressure but it is just soft brass. I can show you some brass you would think is "just right" but is serious overpressure based on MV. You can see some overpressure without high MV if you jamb the bullet into the lands. You get what I mean right?

I am not telling you it is not valuable just that you have to do a lot more than a "proof or test" load to tell you what the "ACTUAL" pressure is in the case. I have read much of the HUGE QL manual. Printed that whole dang thing including the exterior ballistic manual and the more you read it the more you realize the enormous complexity of internal ballistics
 
#13
Re: Quickload tweaking - some observations and ??

Yes, it's enormously complex and the variables are many. But Quickload in and of itself is neither worse or better than some or most of the manufacturers manuals. Where it is useful is to try and duplicate manufacturer loads and with a strain gage it can get you where you want to go. For instance, can you tell me from any of your published data what reduction in powder is necessary to convert a 338-378 Weatherby from a 200gr Nosler factory load to a 210gr Berger Tipped TXS using the unknown factory powder that was in the factory load? It's extremely tricky unless you have a baseline from the factory load using a strain gage and then working up to what a TSX bullet can do using the strain gage. This is a scenario where a strain gage works beautifully. Yes there are other scenarios which strain gages are not the most useful. The reason I did this was because I acquired a bunch of 200gr factory stuff for $30/box and turned it into $100+/box stuff just by having the right equipment. I wouldn't even attempted this without a strain gage as Weatherby ammo is hot from the beginning.

From what I can tell, you're suggesting that the internal ballistics are somehow vastly different than what can be measured for the same energy it takes to distort the outer barrel wall. I can't see that there's much difference going on other than what's happening to the brass. And I wouldn't be using an unknown brass to work up pet loads. That doesn't make any sense to me.

Here's another scenario that a strain gage works very well. At the time Reloader 17 wasn't even in QuickLOAD.

http://www.6mmbr.com/reloder17.html

There's only so much resource a person has available to achieve a desired level of performance from a custom load. QuickLOAD is handy but for me it's just one piece of the total puzzle of a complete set of tools to get you outside the box, if that's where one is headed.
 
#14
Re: Quickload tweaking - some observations and ??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: TwoGun</div><div class="ubbcode-body"> ... Quickload in and of itself is neither worse or better than some or most of the manufacturers manuals.</div></div>
QL is very accurate in its predictions of my MVs, and I mean within 10-15fps of my chrono measurements usually. I'm mainly using Varget for 308 and H4350 for 6mm rounds, and haven't used it with 4831SC for 260 yet (am using the well tried Terry Cross load). I just ordered the V3.6 QL data update so I can play with IMR 8209XBR. You have to tailor it for your case dimensions and volume (measure the water volume of your fired cases), barrel length, and environmental conditions. Most of my barrels are Schneiders, but I expect that some barrels won't give accurate results without some tweaking of the barrel friction parameter.

QL is excellent for parametric studies (e.g., how much more MV will I get with a longer barrel or more powder?) and comparisons (e.g., how full will the case be if I use powder X to get the same MV as I get with powder Y?). All of these applications are more useful than any manufacturer's manual that I've seen, unless you are using a powder or bullet that is not in the database. For example, it took awhile for 115DTAC and 8209XBR data to become available for QL users who were already reloading with them.
 
#15
Re: Quickload tweaking - some observations and ??

QL is very accurate ...once you've got it dialed in. But if you change one component (other than charge weight), more times than not, all that accuracy goes to hell in a bag of skittles.

If you'd like to speak with the oracle hisself, QL's author, Helmut Brömel, sometimes comes up for air at the 24 Hour Campfire.
 
#16
Re: Quickload tweaking - some observations and ??

For my QL is very accurate, in my load with N140 and SMK 175 bullet, in a custom case, I have it starting from a lapua 30.06
For example I trim it at 51.80 mm accordingly to my rifle measures, check capacity with water ecc ecc....... the prediction of QL is 1% less of my actual crono data
So I'm very satisfied with it

QL.png
 
#18
Re: Quickload tweaking - some observations and ??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: davide</div><div class="ubbcode-body">if my topic doesn't match with QL policy please removed it...</div></div>
The issue with QL is when people ask for someone to run data for them for their rifle when they don't actually own a copy. You posting what works in your rifle wouldn't be a problem.
 
#20
Re: Quickload tweaking - some observations and ??

I bought QuickLoad about the same time I got my 260 Rem. I knew it was going to make me dive back into reloading.

I found it to be of limited usefulness. Maybe it will be more useful/accurate for 308, but that is such an easy cart to reload, I won't use QL.
 
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