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I can't get quick load to match my chrono.

A

Aflac

Private
Full Member
Minuteman
May 27, 2013
91
1
New Mexico
Are there any quick load experts here? I just learned about the optimal barrel time paper and want to give it a try. I graphed mussel velocity vs powder charge and then ran quick load for the same numbers and graphed that against it. The slope of the measured numbers is a little deeper than the quick load numbers. So at the bottom of the range quick load will be fast and at the max loads it's slow. I measured case capacity and used my measured results and have tried adjusting burn rate. But burn rate just moves the line up and down. It fits not adjust the slope. Is there something I am doing wrong? Or is this all just within margin of error?. Our is my chronograph out to lunch? When graphed they all appear very linear, just with different slopes.
180 gr smk 308
Varget. Chrono avg. Quick load. Chrono max. Chrono min
36.3. 2099. 2107 2109. 2086
38.1. 2210. 2212. 2218. 2196
39.9. 2334. 2317. 2347. 2314
41.7. 2449. 2423. 2473. 2437
 
I'm no QL expert. I've got a couple mates that do it for me for my rifles with my supplied specs. Here's what I've found. Its close (usually) but not perfect. This is from both mates. Even being given the exact same info they regularly come back with slightly different charge weights and velocity for my OBT. Never really figured out why but haven't really looked that hard into it either. What I use it for is putting me in the ballpark to narrow down my testing to more specific areas. Some /rifles/loads that I'd worked up before getting QL info came up pretty close to where I saw best accuracy in real world testing. Results are usually within about 1/2gr charge weight and under 50 fps velocity difference but can go either way. So I'm not jumping on the my chrony is reading fast or slow as depending on the load some are higher some are lower.

Same with factory load velocities. Usually within 30 ft/sec of claimed velocity but can be higher or lower. I only want the chrony data to get me close. Its the real world verification after that that matters.

One QL prediction had the velocity about right for a load I'd worked up previous but the charge weight was SIGNIFICANTLY out. I'm running 50.2gr WIN748 behind 125gr pills in a couple 308wins for general hunting and worked up to max in my rifles of 53gr. Now I can't remember which was it was but QL for that velocity had either the charge weight down 4gr and pressure higher or charge weight up 4 gr (well over max) and pressure down at a safe level. iirc it was the latter and if I'd gone straight to QL figures theres a good chance I'd have to pull all my loads.

Remember QL is a prediction and not gospel.
 
Most chrono's have a +/1 1% accuracy range.... which would be somewhere around 40-50fps from your numbers. I'd say your're pretty much matching QL predictions.
 
Frogman is right. At the highest velocity avg there is only a 1.02% difference. One thing you can try to get it closer is adjust your bullet weight and see what happens. But again 1% is within range.
 
Yeah I tried bullet weight and it didn't make much of a change. But if the answer is that it's close enough then I'm happy. I just did not like the slopes being different and wanted to ask more knowledgeable people before I started making ammo of it. Thanks for the answers
 
Keep in mind that two identical barrels can have 50-100fps difference between them...you as the shooter can influence the velocity by how hard you hold the rifle. Combine that with +\- 1% chrono variance I'd say you are right on target with QL Predictions. Either way, if the load shoots well on target, get your avg chrono velocity and run with it despite what QL is saying...
 
One other thing to check is that your bullets are actually the length that QL says they are. I've had 130 VLD's that aren't so change it to what dimension bullet your using.
Also be sure to adjust the temperature if you haven't already. QL uses a base line of 70 degree's. So if your conditions we're different than that when you chrono'd the results won't be as close either.
As said above it will get you close on most calibers but its not perfect because there are too many variables between rifles, shooters and components to match up to real world.
With that said QL still kicks ass for getting info without sending one round down range !
 
Things to check are case length, case volume, bullet length, OAL. These are all factors in QL. Last but not least is QL is a program that "projects" or estimates velocity and pressure. I would never expect QL to match chrono numbers, while they may be close the chance of matching is slim.
 
Hmmm, I did miss the twist rate, I got barrel length, case volume, case length, bullet length. I will take a closer look for twist rate, I wonder if that will make a difference. But again thanks for all the help, the more I learn about reloading the more I find I dont know. And I just dont like taking any chances when I am purposfully designing explosions next to my face.....Though I will admit I geeked out for a good 5 days on that optimal barrel time paper when I read it.
 
The four things you have listed are what you need. I get really anal sometimes and find a bullet that is the exact length as the bullet length given by QL and seat it. I then measure the Cartridge length and enter that. The more accurate you are with the data input, the more accurate QL will be with predictions. Twist rate normally is associated with Ballistic programs as a function of bullet stability. Good luck.
 
I have to add 4" of barrel to one of my rifles to get QL to match actual real world numbers. Also, I don't know if its bc of the fast barrel or what (broughton 5c 30" 1:10) but my input data NEVER even comes close to real world data.
 
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