Regarding QL

[308sako]

I've recently been working with a 6 XC short barreled Shilen "match grade" 1 in 14 twist rifle. I have come upon a load that the barrel likes and is giving great brass life, however QL is not accurate in predicting the velocity achieved.

I have weighed numerous fired cases with and without water and come up with 49.8 grains of H2O, a 1/10th different than QL's norm. Barrel length has been input to the breech face and with a fired case inserted, the difference from that is less than 10 fps. Since I am using several different scales to verify the charge weights... I am at a loss as to what to do next within QL to balance the results to the observed.

Bullet used is the Sierra 70 grain MatchKing the Powder IMR 4350 lit by primer Cci BR2, with a cartridge overall length averaging 2.475" which is about -.005" from the lands in this chamber. Actual chronographed velocity 3385 ft/secs, Oehler 35P 20 rounds, SD 9.

QL estimate: 3283 ft/secs, 101.1% fill, 90.48% burn Ballistic efficiency 21.3%

Suggestions and advise appreciated.

 

[Steve Blair]

Change the burning rate factor (Ba) to match. Remember to correct to muzzle velocity.

 

[Nomad47]

Steve's advice is the first thing we do to 'calibrate' QL. You can also tweak weighting factor, shot start pressure, and bullet weight. Chris Long says adjusting bullet weight simulates differing barrel frictions. So even though you are shooting a 70 grain bullet, you could enter 68 or 69 grains as your bullet weight to get QL's velocity up. But you also need to watch pressure. Adjusting the wrong thing in QL could make it lie to you as far as pressure goes.
Chris Long suggests shooting two loads 1 grain apart, then adjusting the four parameters until QL tracks the two velocities obtained with the two loads.

 

[AP2020]

Change the burning rate factor (Ba) to match. Remember to correct to muzzle velocity.

+1

 

[308sako]

Thanks, I'll give the Ba a nudge.



So late this evening I delved into the occult of Ba alteration... F'n magic I tell you. Ba went from .5150 standard to .5390 and matched my data with spooky accuracy.

I have learned a lot, or gone crazy... either way thanks.

 

[louielouie]

I went back and checked my case capacity after adjusting the Ba for the velocity of a middle-of-10rd-ladder test. While adjusting the Ba got my velocity on in the middle charge, it wasn't until correcting/adjusting the case capacity that the 'slope' matched up (within 10 fps) of all the other powder/velocity points.
Further adjusting the 'Weighting factor' seems to move the slope up or down on the 'y' axis.

 

[Nomad47]

Good info, louielouie. I average the water capacity of five cases after the first firing. I should probably do another average after cases have 3 or 4 firings.

 

[normmatzen]

I, too, am in a constant battle to get accurate data from QL.

But, sometimes we forget little things. I recently started using a MagnetoSpeed chrony. I monitor every shot in practice. I have found that although the point of impact goes up as much as 1 MOA, the accuracy or tuning does not change (I use a tuner on the barrel).
I had two batches of rounds ( 6BRX ) some with full length sizing and some with LEE collett neck sizing only. The difference in case capacity is small, but real. I found that at ~3000 fps, about 18 fps difference due to case capacity difference.
I think we are all too easily expecting the digital world to be spot on . I am an old analog engineer and I know digital is not a panacea! GIGO, remember that old adage? For the young guys, that means garbage in, garbage out.

We must be very aware of a lot of second order effects or soon we have first order errors!

So, 18 fps here and 10 fps there etc. and pretty soon we have a 100 fps error.

Quickly, I can think of a number of second order errors, actual bore diameter - alters friction, actual case volume - alters initial pressure, actual powder batch burn rate - obvious. And, what about different primers? Many folks have documented velocity differences with different primers. QL doesn't have a handle for that!
So, each time I try a new load in QL, I consider what I should expect for accuracy. My 6BRX is a pretty stable package and I get pretty accurate numbers, but for my 7X57, my grandson's 7X57 and my brothers 7mm REM MAG as well as misc 30-06 and K31 loadings on various brand cases and powders, I am happy to get to errors of 50-75 fps. And, I use the results as guides, not absolutes!

 

[SDDasher]

I was just talking to a buddy this morning about these very issues with QL. I wish someone would list those things that can be "tweaked" in QL with the attending way to make the adjustments. I know about the burn rate but what about adjusting for different lengths in our brass vs QL or how to enter a Hybrid bullet data not listed in QL's library? There are a number of other things I am missing but you QL guru's get my drift. That would be an incredible primer for those of us technically illiterate using box programs.

 

[Steve Blair]

The QL manual describes all those areas well. There are several articles and numerous posts on this site. The software's manual is always a good place to start.

 

[SDDasher]

The QL manual describes all those areas well. There are several articles and numerous posts on this site. The software's manual is always a good place to start.

Mr Blair;
Thanks for all your help.

 

[Nvreloader]

What would the first steps be, in order to do adjust/calibrate QL?
When FIRST building a load for an unknown case, you have never loaded before?

1. Change the burning rate factor (Ba) to match fps readings.

2. Tweak weighting factor.

3. Shot start pressure.

4. Bullet weight.

Tia,
Don

 

[Nomad47]

Looks good to me, Don. But I think Chris Long would swap 3 & 4. I can't remember his percentages, but he doesn't like to adjust any one thing by a bunch. I'm thinking 10% for Ba and bullet weight.
Chris Long says that once he gets QL to track two different charges, he can then adjust charge to be spot on one of his OBT nodes.

 

[louielouie]

One other little thing I've been adjusting is the 'initialization pressure' - I shoot a range of 6.5mm bullets that have a bearing surface of 0.5465 for the 123 A-Max to 0.636 for the Sierra 140 SBT (hunting) and along with primers, we can establish some kind of values:
(900 * b/s length) + 3134 = init pressure so the 123 A-Max is 3626 psi (default) while the 140 SBT is about 3706 psi.
If QL automatically add 1000+ psi for Barnes solids then there must be something to it...

I usually use Wolf primers but if I try BR-2's I add 200 psi and maybe 300 for Fed GM210M. It's not exact and I may be totally off but that's what empirical values I've arrived from my (limited) testing.
I don't even wanna think about neck tension...

 

[savageshooter86]

talked to Chris on another site and am very interested in the chronograph and tune QL to get your OBT and be very close to your accuracy load. This sounds like a lot of saved components and time. Find your OBT and load and shoot then slightly tune the load and there you go. Sounds too simple but looking at his targets and method appears it works for him and apparently a lot of other shooters.

Now I know this doesn't mean that there isn't any work to be done with your load and actually shooting and fine tuning

 

[ftrrookie]

Great info guys. A couple of questions. First, what does OBT stand for? Second, I've been playing around with QL today trying out some of the suggestions in this thread. I got it close but still about 20 fps off from actual. Until I changed the powder temp setting. QL says not to change this when using "temp insensitive" powders (I'm using Varget). But when I changed it to the actual temp (88 degrees) it jumped to just 3 fps from actual. Do you QL Gurus mess with the temp setting or could this get me into pressure trouble?

 

[Steve Blair]

Great info guys. A couple of questions. First, what does OBT stand for? Second, I've been playing around with QL today trying out some of the suggestions in this thread. I got it close but still about 20 fps off from actual. Until I changed the powder temp setting. QL says not to change this when using "temp insensitive" powders (I'm using Varget). But when I changed it to the actual temp (88 degrees) it jumped to just 3 fps from actual. Do you QL Gurus mess with the temp setting or could this get me into pressure trouble?

[br]
Optimal Barrel Time http://www.the-long-family.com/OBT_paper.htm [br]
I don't use the temp setting unless it's double base powder.

 

[louielouie]

My only other comment is that when using the OBT nodes produced from Chris' spreadsheet, the even-nodes seem to work but the odd-numbered ones do not. I used his original formula which produced a different odd-node value and that *seems* to line up better with my guns w/24 ~ 26 in. barrels.