Range Report Quickload accuracy prediction

[ReaperDriver]

I'm about to pull the trigger (so to speak) on QL and wondered if it is useful for accuracy predicition based on OBT or something similar? I know it pretty accurately predicts MV, pressure and such. But not sure about what output I would look at (I'm looking at the demo page right now) that would give me an indication if X load is the optimum load for a particular barrel.

Is QL worth the $150?

 

[Ratbert]

Re: Quickload accuracy prediction

Um no.

And even accuracy of the MV prediction is kind of an amorphous goal. However I still enjoy playing with it and it is useful for matching up what MV you're getting with what sort of pressure spike ballpark you're likely generating. Going to depend on how much $150 is worth to you, in the end.

 

[sobrbiker883]

Re: Quickload accuracy prediction

I've has folks run numbers for me based on case capacity, cal, bullet, barrel length and powder I wanted to use. The resulting chart, when compared to an OBT chart has consistently given me loads the run moa or better without wasting a lot of components or range time.

I always seem to forget to buy a copy when I've had the dough....

Anyone want to run me a 6.5 Creedmoor table?

 

[Fred_C_Dobbs]

Re: Quickload accuracy prediction

QL's usefulness in OBT is not in the accuracy of its MV predictions but in its linking of MV to barrel time.

Based on your cartridge's particulars, QL will predict a certain muzzle velocity along with a particular barrel time (barrel time = dwell). As MV goes up, barrel time goes down and vice-versa. The OBT theory says that for a given length barrel, certain barrel times will coincide with an accuracy node. So you fiddle with the charge weight until QL's prediction for barrel time matches an OBT and that's your OBT charge weight.

I started out using the OBT-predicted charge as the middle load for OCW testing but have found that tends to be redundant because the OBT-predicted load almost always also is the OCW load. It can be astonishingly accurate.

You will have to tweak QL a bit to make it work well. Measure and weigh your bullets and measure your case's capacity and correct those numbers in QL's factory data. Then load up a handful of rounds for MV testing. From the results, you can correct your powder's burn factor to make QL's prediction match your range data. Once you've done that, you know QL's predicted barrel time also is correct. Then you can adjust the charge weight in QL to make the predicted barrel time match one of the OBT accuracy nodes. QL even has a function that will tell you every powder in its database that's capable of producing your requested barrel time based on pressure limits you also set.

The last new load I worked up with OBT, the OBT predicted load also was best in the OCW test so if I'd skipped OCW I could have had a load ready for seating depth tweaking after firing just three rounds. The longer I use OBT on a particular rifle, the better my feel for the process gets and the more compact the process becomes. That load, BTW, shoots 3-shot groups of 2"-3" @400 yards, averaging about 2.4".

I always load up foulers with a lighter charge anyway so this one time I decided to do an experiment to further test the whole OBT theory. I figured that if OBT is to be believed, I should be able to use the same data I'd just used for my "production" load and just jump to another accuracy node and have it be equally as accurate. So I reduced the charge weight until QL predicted a barrel time that was two full accuracy nodes slower than my production load. My new foulers shot 1/2" @100 yards and QL missed the MV by just 9 fps.

 

[ReaperDriver]

Re: Quickload accuracy prediction

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Fred_C_Dobbs</div><div class="ubbcode-body">QL's usefulness in OBT is not in the accuracy of its MV predictions but in its linking of MV to barrel time.

Based on your cartridge's particulars, QL will predict a certain muzzle velocity along with a particular barrel time (barrel time = dwell). As MV goes up, barrel time goes down and vice-versa. The OBT theory says that for a given length barrel, certain barrel times will coincide with an accuracy node. So you fiddle with the charge weight until QL's prediction for barrel time matches an OBT and that's your OBT charge weight.

I started out using the OBT-predicted charge as the middle load for OCW testing but have found that tends to be redundant because the OBT-predicted load almost always also is the OCW load. It can be astonishingly accurate.

You will have to tweak QL a bit to make it work well. Measure and weigh your bullets and measure your case's capacity and correct those numbers in QL's factory data. Then load up a handful of rounds for MV testing. From the results, you can correct your powder's burn factor to make QL's prediction match your range data. Once you've done that, you know QL's predicted barrel time also is correct. Then you can adjust the charge weight in QL to make the predicted barrel time match one of the OBT accuracy nodes. QL even has a function that will tell you every powder in its database that's capable of producing your requested barrel time based on pressure limits you also set.

The last new load I worked up with OBT, the OBT predicted load also was best in the OCW test so if I'd skipped OCW I could have had a load ready for seating depth tweaking after firing just three rounds. The longer I use OBT on a particular rifle, the better my feel for the process gets and the more compact the process becomes. That load, BTW, shoots 3-shot groups of 2"-3" @400 yards, averaging about 2.4".

I always load up foulers with a lighter charge anyway so this one time I decided to do an experiment to further test the whole OBT theory. I figured that if OBT is to be believed, I should be able to use the same data I'd just used for my "production" load and just jump to another accuracy node and have it be equally as accurate. So I reduced the charge weight until QL predicted a barrel time that was two full accuracy nodes slower than my production load. My new foulers shot 1/2" @100 yards and QL missed the MV by just 9 fps. </div></div>

Thanks! That's exactly the kind of info I was looking for.

Couple of quick Qs:
1. I realize Garbage in = garbage out. How hard is it to tweak QL as you suggest to get that data correct? Was that a laborious process?
2. Is the OBT affected by just barrel length? Or does profile, composition, rifling type, etc all affect that as well? Is that lind of stuff go into the calcs?

 

[Fred_C_Dobbs]

Re: Quickload accuracy prediction

In reverse order, the OBT theory holds that nothing about the barrel matters in the harmonics that determine its accuracy nodes except length. Rifling might affect barrel time (as in dwell) but it doesn't affect the timing of the optimum barrel time nodes.

The hard part was figuring out what not to screw with. After that, it got pretty simple. You just confirm that your bullet's dimensions (weight, OAL, and length of boattail), a FF case's capacity (measured in grains of water) and your anticipated COAL all match what's in QL.

After that, all that's left is to adjust either "burning weight factor" or something called "weighting factor" to make QL's predicted MV match your range data. Some folks prefer to use "weighting factor," including the guy who wrote OBT. I use the burn factor because I've screwed with the both of them and just had better success with it than with weighting factor. YMMV.

EDIT:
One other thing. Whichever pressure setting you tweak, the tweak can change over time. I just opened a new bottle of Varget and my MV went up 33 fps (and my accuracy suffered a bit for it). The new bottle was bought at the same time as the one that just had run out, it was the same lot number, bought on the same day and the two had sat side-by-side since new. The difference is that the powder in the bottle that had been opened longer had absorbed enough humidity that a given volume weighed just a tiny bit more. So I tweaked burn factor, which reduced my OBT charge weight by 0.6 grains and got rid of those extra 33 fps.

 

[ReaperDriver]

Re: Quickload accuracy prediction

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Fred_C_Dobbs</div><div class="ubbcode-body">In reverse order, the OBT theory holds that nothing about the barrel matters in the harmonics that determine its accuracy nodes except length. Rifling might affect barrel time (as in dwell) but it doesn't affect the timing of the optimum barrel time nodes.

The hard part was figuring out what not to screw with. After that, it got pretty simple. You just confirm that your bullet's dimensions (weight, OAL, and length of boattail), a FF case's capacity (measured in grains of water) and your anticipated COAL all match what's in QL.

After that, all that's left is to adjust either "burning weight factor" or something called "weighting factor" to make QL's predicted MV match your range data. Some folks prefer to use "weighting factor," including the guy who wrote OBT. I use the burn factor because I've screwed with the both of them and just had better success with it than with weighting factor. YMMV.
</div></div>

Cool. How much does the accuracy of the chrono affect your tweaks to get QL to match your actual range MV? I am currently using a CED M2 and I'm fairly confident the MV is close. But I'm sure other chrono's like the Ohler 35 or something would be more accurate. I know that my CED is typically about 10-20 fps different than my friend's Ohler shooting the same load out of the same rifle. Is that going to throw the calcs off too much?

 

[Fred_C_Dobbs]

Re: Quickload accuracy prediction

I use an M2 as well. If it's accuracy is other than adequate, it hasn't seemed to affect my ability to work up loads with OBT.

Worst case, you expand the number of incremental loads you use for OCW testing. 20 fps probably is under half a grain charge weight so as long as your min/max OCW loads go a full grain either side of OBT's predictions, you chould have it well covered.

If you run a couple of iterations of OBT and notice that the best OCW load always is a consistent charge weight (or MV) above or below the OBT-predicted load, take note of the difference and in the future, you adjust your starting or middle OCW load accordingly. In part, that's what I was referring to when I mentioned gaining experience doing OBT with a particular rifle.

 

[1000yard]

Re: Quickload accuracy prediction

I bought QL in Feb 1999, from Hartmut, at the SHOT show, and have been using it since(have had to upgrade and update a few times)
It has saved me a bunch of time/money. Works well for me.
remember garbage in = garbage out.

 

[ReaperDriver]

Re: Quickload accuracy prediction

Just ordered my copy this am. I'm looking forward to playing with it and seeing how well it works. I have several different powder, case and bullet combos that I haven't gotten around to doing load development on yet, so it should be interesting.

 

[Clark]

Re: Quickload accuracy prediction

I am using for more simple things than Dobbs.

I just ordered an upgrade this week from 3.4 to 3.6.
The CD cost me $15.

I have lots of cartridges that I handload and am getting ready for hunting elk at long range.

What will give me the most power at 500 yards, 7mmMag, 300 Win Mag, or 338 Win mag, with the barrel lengths I own and the bullets I can get this month?

Per Quickload, that turns out to be 7mmRemMag 180 gr VLD, 26" Re22.

It also helps me make the chart for adjusting my scope elevation and windage.

With this chart on my range finder, I shot 5 deer last year between 329 and 510 yards.

It also gives me the math so I will stop shooting at walking animals at 600 yards.

 

[ReaperDriver]

Re: Quickload accuracy prediction

Thanks Clark. My copy should be waiting on me at home today. I'm looking forward to learning how to use it to best effect.

 

[dar1246]

Re: Quickload accuracy prediction

I use QL for finding different powder combos for a new bullet selection. It helps kinda of with pressure and case capacity.