I broke down and bought a copy of QuickLOAD to play with, I'd like to make sure I'm looking at the right numbers to get a prediction of optimal barrel times.

This is for a 7mm-08 Rem.  Barrel length is 26".  I'm using LC-16 brass that has been fired multiple times and I have measured the water capacity of those fired cases to be an average of 54.4 grains.  I'm using a Hornady ELD-M 162gr bullet (#28403), COAL is 2.950" and Reloder-17 for giggles.

From an OBT chart, the 5th node for a 26" barrel is 1.3295ms.

In QuickLOAD, I pull up the Hornady bullet and change the cartridge length to 2.950 from 2.800.  

In the selected cartridge window, I pull up 7mm-08 Rem and change the case capacity from 55.0 grains to 54.4 grains.

In the charge window, I pull up Alliant Reloder-17 and change the charge wt to 43.2 grains.  I also changed options/step window/increment step width/user defined/in weight increments to 0.1 grains.

I calculate the charge variations and the output gives

So QuickLoad is predicting the barrel time of 1.329ms for 43.2gr of Reloder-17 which is real close to the value I want.  Yes, I know to work up to that load, not load to that straight out of the gate.

What confuses me is the QL barrel time.  The 'B_Time ms' in the charge variations output is the same as the results field 'Barrel Time 10% PMax to barrel.'  But when I look at the pressure/velocity graph and move the mouse pointer to the far right where the bullet exits the barrel, the graph axis is right at 1.360ms.  In the more results window, the 'time elapsed since 10% PMax' is 1.314ms.  So which do I compare to the OBT time to?  The 1.329ms from Barrel Time 10% PMax' or the graphed result of 1.360ms when the bullet actually exits the barrel?  My feeling is to ignore the graph axis and go with the printed barrel times.

In a related question:  How close are the predicted QL velocities to real life?  The reason I ask is I'm highly suspicious my chronograph is giving false readings - approximately 100 fps higher than what they ought to be for a Varget load in this rifle.  I had data from the chrono last October for a 77gr SMK 556 load that I thought was screaming out of the rifle.  When I used a friend's LabRadar in Atlanta, it was 100 fps slower than what my chrono said and much closer to what it should have been according to the reloading manual.  The chrono is giving what I think is the same 100 fps error with this cartridge, but I have no way to check at the moment.  (At least until I get to a long range and check bullet drops.)  I know you can mess around a little with the 'Burning Rate Factor Ba' to force the prediction to match your measured muzzle velocity, but I'd have to change it so much for that 100 fps presumed error that it can't be right.  Plus when I tried to do it, QL shows a dangerous load and my work up, the bolt lift, brass life and primer say it's not.  I think it's time for a new chronograph.

I'll be interested to read the responses.

I've been thinking about buying QL as well. Kind of interested to see what you think of it.

I ordered yesterday, so I'm in to learn. Well actually I might be able to contribute something. A friend ran my numbers for a 90 gr SMK 223 load, measured velocities with Labradar we right at 100 fps slower than expected. Might be that lot of Reloder 15, might be chamber/barrel, hard to say for sure. Variations happen so the fudge factors help you tune parameters to meet your system.

How do u get to the OBT data page? I have used QL for a few months now but haven't come across that feature.

It's not in QL as far as I know.  I just googled "optimum barrel time" and started looking around.  In particular, I downloaded this: OBT Chart

There are a couple of excel files I found, one with macros and the other without that will do the calculations too.

Select: Options/Output window settings/Charge increments of one propellant. Wasn't sure which page you wanted to see lol.

I've been using the 'time elapsed since 10% PMax' number with truly excellent results.  Excellent in that, with high quality bullets like Berger, I'm getting 5-shot 1-hole groups at 100 yards, and 5-shot 6" groups at 1000 yards.

But your post has me second-guessing.  I think ideally, I need to do the OBT method and also the OCW method, independently, and compare results.

I have some experimental data to add - and I also have some changes to make to the initial data.

I actually measured the cartridges instead of going by memory and they measure 2.920", not 2.950", so I lost a bit of case volume there.  They're still 0.020" off the lands.  I also had to start with the next lot of brass - I had worn out what I've been shooting.  So I measured the water capacity of 12 cases that I fired today when I got home from the range.  The water capacity of these new cases averaged 54.49 grains of water, so that gave me a bit of case capacity back.

As I was walking over to my reloading bench yesterday to make the loads, I messed up the charge weight by a grain.  No biggie, I caught it before I got finished loading, but instead of pulling all the rounds, I just pulled the ones outside the range and loaded a couple more test groups.  Since I dropped a grain yesterday and I was using .3 grain increments, the actual charge weights were .1 grains off of what I intended.  No harm, just full disclosure on why I didn't load exactly what I said I was going to load yesterday.

So plugging in the values from today (and changing the weight increment to .3 grains to match what I loaded, here are QL's predictions:



And how did the prediction stack up to reality?  At least within my shooting ability?  (Group number 5 is just stuck behind 1 to make it easier to take the picture, not because it belongs there.)  I only shot 4 round groups because that's how the box of bullets worked out.  Besides, OCW says just to shoot 3 round groups.  In case you're wondering, my scope is down .5 mils from my Varget load zero.  This load is shooting a little high and right of that load.  If it was the same, the rounds would impact in the bottom diamond with my aim point being the top diamond.



My OBT for the 5th node is 1.3295ms.  The best group was loaded at 43.1 grains giving a barrel time of 1.324ms - which just happens to be the closest to the OBT.

Given this, I'll do a 10 round groups later this week with 42.8, 43.0 and 43.2 grains.  These 30 rounds will be out of the same lot of brass I used today, but won't include the same cases I shot today.  This lot of brass is LC-16 .308 resized to 7mm-08 and weigh between 176.6 and 177.0 grains.  The brass prep after buying once fired cases was clean, FL resize to 308, trim to length with a WFT, FL resize to 7mm-08, anneal, FL resize again, deburr flash holes, clean, load.  I'll post results when weather and time permit.



Crappy thing is I have to start a new box of bullets, but at least they're from the same lot number.  I'm making the assumption my OCW will end up being 43.0 grains.

And here's the results of the chronographing I was doing today.  As I said before, I'm NOT trusting it right now, so I'm not bothering to adjust Ba to make the predicted velocities match the measured velocities.  


Anybody know how to verify a chrony?  I'm thinking about making a ballistic pendulum.



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Edited because dropbox is run by a bunch of hosers that screwed up public links

Understand that I have had Quickload for less than a week, but as far as I know, optimal barrel time is not defined anywhere in the program.

This is my understanding of OBT:  The optimal barrel time theory is that the sound wave from the powder igniting moves from the chamber to the muzzle, then reflects back to the chamber, reflects back to the muzzle (albeit at a smaller amplitude each time) etc.  Every time the sound wave gets back to the chamber, it's a node where it's as far away from the muzzle as possible.  This time can be calculated from the speed of sound in steel and the barrel length.  The thought is the sound wave opens up the bore a little bit so the bullet is not held as tightly, so you don't want that effect when the bullet is exiting the barrel.  

In my case, the 5th node is the sound wave is back at the chamber for the 5th time.  I'm using Quickload to provide an estimate of the barrel exit time to make small changes in pressure by slight charge changes or seating depths to cause the bullet to leave as close to that time node as possible.

I don't know if I believe it or not.  There seem to be a lot of people that do.  But I will say in this case, I've never used Reloder-17 before.  I bought some on a whim back in November in AL just to have a different powder on the shelf.  When I started playing around with this 7mm-08 and bought Quickload, I ran a bunch of different powders - everything I had that would work for a 7mm-08 - 223 CFE, 8208-xbr, IMR 4895, H4895, TAC, Varget, Reloder 15, Reloder 17, IMR 4064, AA2230, Win 748 are the ones I see in the shelves from here.  The internet is singing the praises of IMR 8208-XBR for velocity, but by the time I found a good precise load with it in my rifle, I thought it was over pressure.  QL confirmed that.

Reloder-17, with the water case capacity of my LC-16 brass and the length I am loading to, looked on paper to be a best choice in QL as far as case fill, max pressure, and velocity of all the powders listed above.  I also noticed it was the best with the powder burning 100% just short of the muzzle and the predicted barrel exit time matching up with the OBT node at around 43.0 grains.  I loaded up an OCW test series and shot it.  The best group was right where the predicted QL barrel time matched up to the OBT node.  

Really hard to say if it's a coincidence or not with a sample size of 1.  So I'm posting results here and asking others if they have tried anything similar and if so, am I using the numbers the same way they did.  I am not saying this is a method that will work for anything, I just want to know if anybody else is trying something like this.

That's the goal and why I started with OCW.  Then I got wondering if OCW was somehow related to OBT, ie, did the optimal charge weight load barrel exit time line up with an optimal barrel time node that gave the most forgiving load.

I'd be happy to find a good load that shot well at +-0.5 grains, +- a grain with a 308 based cartridge would be a bit much to ask wouldn't it? That would be around a 4% difference.  I'm just wanting to try banging steel around 1000-1200 yards, I have no interest in large magnum cases that would take that much powder.

I'm going to the range and trying this out Friday. I'm shooting .308 and reloder-17 is at the top of my list according to QL also for 190gr, 175gr and 168gr bullets. I'm going to load up several test loads from each of those bullets, with one 5 shot group being the closest to the predicted node. So my sample size will be a little bigger, but not definitive.

I have been working with QuickLOAD for three days so I'm still learning but the two .223 loads I found by the blind squirrel method are right on two OBT nodes from the table available online.  That changed me from sceptic to maybe a believer.  

Like you I found the OBT macros and OBT tables.  Interesting these data do not agree with the data published in Chris Long's original article.  Not sure why the OBT node number for the same barrel length would be different or which numbers we should be using.

It is a bit surprising not to see Varget, for example, near the top of the list for heavy .223 and .308.  Not a big deal, just surprising.  The usual suspects are missing.  Not sure why.

I don't know the answer to your question about the difference between OBT shown in the table and the pressure/velocity chart, but I do see the right side of that chart ends short of barrel length.  If you put the cursor on the green line there is a box below showing "Projectile travel (in.)" which is well short of my barrel length.  I also see OBT is defined as 10% pressure to muzzle, not barrel length.  Think I would go with the OBT shown in the lower right chart.  It would be helpful if OBT was included somewhere in the program.

I am unable to save loads.  If anyone else has this problem or found a solution, I would be interested.  The button between File and Options takes me to the save box but when I save and try to reload I get an error message.  I'm on Windows 10.

Great idea to share experiences.  I have a lot to learn.  So far, I'm finding the program highly interesting, very powerful, and potentially a useful tool.

That was my understanding of barrel harmonics also until I bought QuickLOAD and started reading.  Some think it's not barrel oscillation but a change in bore diameter which travels back and forth through the barrel.  If that's true, and I'm not sure it is, you want the bullet exiting when the bore diameter is closed not open I suppose.  I'm not sure about this because we have all experienced POI shift from anything touching the barrel.  Interesting stuff.  

Enough of the theory.  I plan to spend my time seeing what all this means on the target.

I think the the reason for the barrel length being shorter than what it actually is, is that QL subtracts the cartridge length from the barrel length and what you're seeing is the barrel length the bullet actually travels which is not from the bolt face to muzzle.  At least that's what I've come up with.

Reading around the internet, I found another parameter to try and balance which is on the pressure/velocity vs time graph is Z1 - end of progressive burn.  My reading suggests that you ought to try and get Z1 as close to Pmax as possible.  If Z1 is much to the left of PMax, your powder is probably too fast for the load.

So going through my powder inventory, I've found that 41.0 grains of CFE 223 in my 26" barreled 7mm-08, 162gr Amax seated to 2.920" with my case capacity of 54.49gr of water.  I just happened to have 5 pieces of brass left in this lot, so I figured I'd load up a mostly blind test.  I loaded 1 at 40.0gr, 1 at 40.5gr and the remaining 3 at 41.0gr so I could sneak up on the pressure a little.  QL predicts a barrel time of 1.329ms, right on top of the OBT node I was using before.  It will be interesting to see how those last 3 rounds group.

The reason I didn't pick CFE 223 to start is the case is only 86.7% full.  I've always heard you want the case as full as possible.  With that said, I've also read you don't want between 98% to 101% because depending on the individual case, some loads could be compressed and some might not be - which gives a bit of inconsistency in the pressure from shot to shot.


Z1 right on top of Pmax



Barrel time 1.329ms.  Even so, I don't think I'm willing to give up the 100fps with increased pressure since I'm working towards a long range load.  But I want to see how the QL prediction holds.

The Reloader-17 load has Z1 to the right of Pmax which the internet says the powder would be a bit on the slow side.


When I went with Reloader-17, it was 96.5% full.

I'll post a pic of the CFE-223 3 round group when I post the Reloder-17 groups.

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edited because dropbox is run by a bunch of hosers that screwed up all public links

Z1 vs. Pmax.  One more thing to think about.

My optimized load has the Z1 to the right of Pmax.  Hoping that means I don't need to change powders but can bring the two together by seating depth.

Will see how that works.

Looking forward to seeing how this translates to the target.

I went back and looked at some of the loads I was planning on loading to see where Z1 was in relation to Pmax. Some of my loads have everything spot on. I'm at a node, Z1 and Pmax are equal and it's not overpressure. So I can compare that 5 shot group to the ones that are not. Some are supposedly on a node but Z1 and Pmax aren't close. Should be a fun Friday and I'll report back.

When you tune the QL model to your observations (accurate chronograph data) and enter the measured case capacity, ambient temperature, and adjust Ba, your QL model is now the gospel, and not an idealization.  You have trued your model to your observations.

With large charge weight variations that you give (1.5-2gr), you're going to need an enormous case - like a belted magnum - if you hope for any consistency at all.  1.5-2gr in a .223 case will be an enormous difference.

I'm editing the picture links above.  Apparently dropbox changed their public folders today.

I have so many data points and not enough brain cells left lol. What is the best way to test this theory out? I have multiple bullets in .308 data I can load, just need an idea of where to start. Example:

.308 168gr Nosler HPBT
22" barrel
56.88 h2o
2.000 case length
2.800 COAL
40.0gr AR-Comp
89% case fill

This load is on a node at 1.201" (node is 1.2018" according to the chart I downloaded) and Z1=Pmax on the graph. I can go up to the next load at 42.1gr (94% case fill) but the Z1 is not spot on with Pmax.

Should I load 5 shots at 40gr and 5 at 42.1gr and compare them to see if Z1=Pmax matters? Should I load 39.7, 40.0, 40.3 to see if being on the node matters? All of the above?

The answer to your question is "all of the above."  More data is always good.

I found a very useful tool in the Propellant Table Setup Form.  Click the box for the barrel time of entry load and the lower left table will give you other powders and loads that match you OBT.  Very interesting to see other powders with the same OBT which might produce lower pressure or higher velocity.  

I am very pleased with the software.

Key question is whether an OBT load is an accurate load.  I have back tested accurate loads and found them to be on an OBT node which is encouraging.

Your data might be a good test of the OBT hypothesis except for the n of one of course.

Good luck.

The only reason I'm posting this is because I said I would.  My son and I were miserable at the range today, neither of us were happy with our shooting.  35 degrees and a 10-15mph wind makes for some cold fingers and toes.  I feel like I wasted a half of box of bullets, but it was still cheaper than going to a movie.  I'm going to repeat this test when it's more pleasant shooting weather.  I didn't count a couple of my shots, I know I yanked them.  Hard to be still when shivering.



1=42.6gr, 2=42.8gr, 3=43.0gr, 4=43.2gr

The 3 shots with the CFE223 load were under an MOA.  The bullet in that group I didn't count was the first shot of the day at the right hand target that was way off.  I didn't feel like going down range to put up a new one.

It rained some today so couldn't get to the range. I got a swfa ss 12x42 scope I need to sight in though, very nice looking glass so far. Should have time tomorrow to shoot if it stays clear.

So, OP what is your opinion of it now? Really thinking about it, guess I will need to get a aux cd drive for the surface.

I think it's a very useful tool.  I'm not holding my crappy shooting on a day I was freezing against the predictions.  Best part of it was it confirmed an 8208-xbr load was too hot.  Primers didn't look bad, no problem with bolt lift, but the cases were killed after about 3 shots and then would pop a primer for no apparent reason.  Had 2 go in 100 shots or there about.

Monday afternoon is looking pretty good as far as weather.  I hope to try the last test again.

Made it back to the range yesterday afternoon.  Here are the results, but I need to use shooter's excuse #87:  I forgot my bipod and had to improvise a shooting position off my range bag.  I was hanging off the bench and even had one knee down on the ground and the best I could hold was about 3/4 of the inner diamond.  So at least a 1/2" of these groups was me.  I didn't count a couple of shots because I knew they were bad when they broke.



I shot everything round robin, 1 round 1 to 6, then next starting on target 2 and going 2-6, 1, then starting on target 3 and going 3-6,1-2, etc.  Target 1 got shot at twice as the first target since I loaded up the rest of the box of bullets and had 7 rounds for each charge.

If you're into OCW, all the loads, 42.4, 42.6, 42.8, 43.0, 43.2, 43.4 were keeping a consistent point of impact.  Somewhere between 42.8 and 43.2 will be where I settle.  If you're reading it differently, please let me know.

The rifle is going to be down a while, I'm going to try my hand at bedding the action.

*****Edit
Well, forgot my conclusion.  Once I adjusted the QL model with the actual fired case volume, it predicted a barrel exit time that lined up with an OBT node at 43.0 grains.  In the range where I'm going to settle.  If I had trusted QL, I'd been in the ball park immediately and could have saved shooting quite a few rounds while narrowing in where I wanted.  The adjusting for fired case capacity was the key.