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QuickLOAD weighting factor?

I've read the linked article re: QuickLoad and understand the comments on the weighting factor.

Yesterday, I went to the range and tried a whole slew of different bullets, and powders, simply to check the accuray of the program. I got it just last week.

The temp was between 18F and 24F over the course of the session, and I took that into account when loading the data into the program as an "after-action" report. With Hodgdon Extreme powders, of course, I didn't factor the temp.

I was shooting mostly .270 Win, and with some tweaking of the weighting factor, I can get pretty close to the actual chronoed velocities....but here's my question. I'm having to tweak it, in most cases, a lot.

In fact, one load of RL-22 at 57.5 grains with 150 grain AFrames clocks 10 fps faster than what the program predicts even with the weighting factor set to zero, and the firing temperature correctly inputted. This seems a pretty drastic tweak, considering what I read in the article. Is this unusual?

I've checked H2O capacities and keyed all the dimensions of my cartridges correctly.

This brings up another question...once you've found the weighting factor that works for a particular powder, that only needs to be changed,or, may need to be) when you test a different lot. Is that correct?

And to ask one more question......I'm beginning to think that the weighting factor is specific to a specific lot of powder, not a particular rifle. Is that a correct assumption?

Thanks

Mike
 
The other area that is pretty much a guess is the initiating pressure. It will make a big difference in your pressure readings, and as a result your velocities. It needs to be adjusted to take into account your jump to the lands, or lack there of.
 
In my experience, the most effective method to "calibrate" QL to range data is to adjust the burn rate parameter of the powder - Ba, and leave the weighting factor close to the recommended for that cartridge. Powder lot variations in burn rate can easily be +-5% in the extreme. Tweaking Ba a few percent can get QL results very, very close to actual measured performance data. I record that adjusted value on the jug of powder so I don't forget it.

Changing Ba is easy: On the QL "Charge" window, the one where you input the charge weight, click the little icon just to the left of the drop down list bar that you use to select the powder. This will turn the powder parameter fields below from gray to white, allowing you to edit them. Just change the value of Ba to suit your fancy, with a larger number meaning a faster burn rate, and higher pressures/velocities. The powder name in the list field will now have ? marks before and after, telling you that the default values are overridden. To recover the original values, just click the icon again, and re-select the powder. This does not permanently change the powder data. You can however make a new entry into the powder database with this new burn rate - in effect a "custom" powder. Read the QL manual for instructions on how to add and edit powder records.

If I am using my PressureTrace instrument as well as the chronograph, I will adjust both Ba and the weighting factor to get both the pressure and velocity to track perfectly. The weighting factor is a qualitative estimate of how much energy the powder is using to accelerate the unburned powder with the bullet. A factor of 1 means that all the powder is moving, and 0 means that it all stays in the case during the burn. It does have an effect on the results, but I recommend that you not deviate too far from the baseline, and tweak Ba instead.

If you have more questions, just drop me an email, or ask the question here. Hope that this helps!

Cheers,
 
Thank you very much! That is a most helpful post.

I'm a fairly conservative reloader by nature, and "burn-rates" are something I've been afraid to mess around with. I'm going to play with it now and see what that will do, while maintaining a .5 weighting factor.

Once again, thanks so much.

Mike
 
You are welcome! As long as you stay in the +- 5% range, you are OK. After all - the rifle is the real thing, and you measured the actual bullet velocity, with no pressure signs!,Hopefully a good assumption!) If the bullet is going X FPS, then it takes Y pressure to do this. Even with bullet, barrel, case, and other variables, the pressures won't be too far off if you match velocities. It can't hurt to play with the program, just be careful out at the range!

Cheers,
 
There are many other variables that make a difference. #1 If you are seating in the lands, I suggest you add 5500-6000 psi to the start pressure,less than QLoad recommends, but it's still important to change the default). #2 Some of the bullet dimensions,weight, length) are incorrect in the data set--you need to manually override. #3 With the Hodgdon powders made by ADI, it works better to use the equivalent ADI data set. #4 Even with the "Extreme" powders I've found some temp correction is important. This is especially true with Varget.

These things may get you closer. But keep in mind that I consider getting withing 25 fps a very "good" match. Here's some things to consider--with the exact same load and same barrel dimensions, we've seen up to 80 fps differences from one barrel to another. AND, even quality chronographs can vary by as much as 50 fps chroning the same load. Two Oehler 35s placed back to back will usually be within 5-10 fps, but if you're talking about Shooting Chronys or PACTS, one machine can easily read 30-50 fps higher than another. Chronies are notorious for being 20-40 fps "optimistic" compared to an Oehler.

Bottom line--if "post-tweaking" you're within 10 fps of measured velocity that's about as good as it gets.
 
Once again, I thank all for the advice. This is some great info that I wasn't able to glean from the Adobe "User's Guide".

Okay, playing with the burning rates vice the weighting factor made for a much more accurate result with velocity predictions, and it made a tremendous difference in estimated pressure. While I would, of course, have approached max loads in small increments regardless of what QL predicted, you guys very likely saved me a lot of headaches, and that's severe understatment. Once again, I truly appreciate the input.

Of course, I have another question......

Has anyone found that the burn-rate of a certain lot of powder can vary from chambering to chambering? For instance, with my 6mm Rem, I can adjust the BR and closely match the actual results with 2 recipes in that chambering. However, when I use the same powder and the same burn-rate in either of my .223 Rems, I have to again adjust the BR to match the chronoed data for those rifles. And not just once, I have to tweak it for each rifle. Even though it was the exact same powder, poured from the same 8lb jug.

IOW, using the exact same powder, I have to use 3 different burn rates to match the chronoed results of 3 different rifles.

Anomoly, or normal?

Mike
 
Mike,

The other main ingredients are seating depth and case capacity. If these are different in your two .223's, perhaps that's the difference??

I don't know how much difference you are seeing, but as the other posters stated, if you are within 50 fps or so, you are mighty doggone close.

Mike

BTW, you know me as scootertrash.
 
How's it going, buddy? :D You snowed in? We got about 1" this AM, and C/S was actually running plows by 8AM. Funny, they don't do that when you really need it.......LOL!

I need to call a couple of our ranchers and see how their dogtowns have survived this weather. We need to get in a late Feb shoot or two, just to dissuade them from poisoning in early spring.

I'm really looking forward to seeing your new "twenties" in action. Maybe I'll get a nice load worked up for my 6mm with the help of QuickLoad & the members of this forum, so you won't get bored again this year waiting for my bullet to get there....

As to the H2O capacity, yep......done all that. Triple and quadruple checked, even. I am having to adjust the burn-rate some from rifle to rifle to get the results correct.

Anyway, back to pondering it some more.

Thanks for dropping in!

Mike
 
Weighting factor has nothing to do with powder, or powder lots, or barrels. It's an adjustment for cartridge efficiency. That is, it's ability to burn powder in the case -vs- half way down the barrel.
A 30 06 would suck in this regard, as much of it's powder counts as projectile weight for a distance down the barrel. Nothing to hold the powder back.
 

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