Quickload (or chrono?) way off for 300 win mag or H1000

[nuclear_shooter]

So, just got Quickload and plugged my current 300 win mag load it to compare. Measured my case capacity right at 93.2 gr H2O , OAL 3.620", 26" barrel, 208gr AMAX, 74 gr H1000, and it underestimated what i chrono'd by almost 200 fps. My friend ran his 338 LM load though and it matched up exactly. I've shot out to 1000ish yards with it, and the dope matched up fairly good, if anything I shot high. Load chronos right around 2810 at the muzzle. As stated, this is my first time with Quickload, so maybe I just missed something obvious. Any suggestions?

 

[Sako man]

Quickload is an estimated guess, chrono is going to be much more accurate. It's as well very difficult for someone to figure out what the issues was not looking at your input data vs shooting conditions. Trying to chase quickload accuracy vs the actual MV is a loosing battle. Examples: a function of MV is ambient temp or sheering friction and a million other variables. If you want to chase that tail by all means do so but I don't recommend it.

 

[bigedp51]

With Quickload to get accurate data you need a chronograph, then you need to change the powder burn rate until Quickload velocities match your chronograph velosities. Until you do this everything that Quickload spits out is just a guesstimate, I also understand that even after doing this there is no guarantee the chamber pressure readings will be correct.

I do not have a chronograph so until I get a chronograph the money spent on Quickload could have been better spent. Meaning Quickload is overrated and needs "tuned" with a chronograph to get accurate data. It does give good estimated data on powders, the percent burned in a given length of barrel and has other good features. But pressures and velocities leave a lot to be desired and manuals give better data for reloading in general.

 

[nuclear_shooter]

So basically you're suggesting something like: http://www.the-long-family.com/Tuning QL to achieve best results.pdf I still expected better agreement (20-50 fps), but maybe the system becomes more nonlinear when you load them out as far as I've got them? I will rechrono some loads this weekend maybe, make sure I didn't misread a 2600 as 2800 . Still, I think I would have noticed that even at 500 yards.

 

[sakobob]

believe your dope, 74gr h1k and 2810 seem about right where it should be.
as said, there is a bunch of variables so don't get to hung up on the quick load data.

 

[nuclear_shooter]

Will try several loads out with a chrono when I get some time and attempt to get a better powder burn rate. Anybody else had similar issues with H1000?

 

[918v]

Did you measure the capacity of a virgin case or one that was fireformed to your chamber? Did you measure your actual bullet, or go with what QL had? What chrono are you using?

 

[nuclear_shooter]

Did you measure the capacity of a virgin case or one that was fireformed to your chamber? Did you measure your actual bullet, or go with what QL had? What chrono are you using?

Yes, I did, it was actually bigger than what QL had, making it even less velocity. I didn't measure the exact bullet mass, but its only a few fractions of a grain off I would guess. I can measure in the morning. The chrono is just a standard Shooting Chrony. I believe it to within a few FPS as I've tested it with several factory loads plus as I said, my dope is pretty much dead on or a little high at 800/1000 yards (as it I shoot over top the target).

 

[918v]

Yes you did meaning a virgin case or a fireformed case? Because that's where you will lose most of the velocity.

 

[nuclear_shooter]

Yes you did meaning a virgin case or a fireformed case? Because that's where you will lose most of the velocity.

Sorry, the brass I'm using was once fired factory ammo that I've been reloading. I have yet to actually try virgin brass, but I do have some norma brass I will try out.

 

[918v]

Did you measure the bullet length? QL's bullet data isn't always accurate. For example, QL says my 175SMK is 1.266" long but in actuality they are 1.235" long.

QL is dead on with the 308 and the powders that go along with it. Maybe their H1000 burning rate is wrong?

 

[nuclear_shooter]

Did you measure the bullet length? QL's bullet data isn't always accurate. For example, QL says my 175SMK is 1.266" long but in actuality they are 1.235" long.

QL is dead on with the 308 and the powders that go along with it. Maybe their H1000 burning rate is wrong?

Good tip. The bullet length was off by about 0.2" and the weight was off by 0.5 gr. I guess longer bullet = less usable volume in the case = higher pressure = higher velocity. Now only 100 FPS off. Burn rate to get proper velocities is now 0.3940. Stock value is 0.3660.

 

[Clark]

In the 1980s there was a Valhalla power meter that cost $2k that the saying was, "You will know you are operating it right, when it gives you the right answer."

I have been posting about Quickload for 14 years.
I think I am getting better at operating it, because the chronograph agrees with the QL prediction more often.

The QL library treats 300WinMag special. It gives different case volumes for different brands of brass.
When I measure the same brands, I get about that much variation, but not much correlation.

The more important tricks are:
1) Change the start pressure for jammed into the lands vs off the lands.
2) The jug of powder you have may act a lot faster or slower than the model in QL library. Get a correction for each jug. My 8 pound jug of IMR4350 requires that I enter 4% smaller into QL to the the right velocity and pressure prediction.
My jug of Varget is right on the money.
My surplus IMR4895 jug acts just like H322 in prediction land.

I do not have enough data on belted magnums yet, but with the Mauser case heads I have overloaded, the same powder will reach the threshold of loose primer pockets at the same predicted pressure in 243, 260, 308, and 257RAI.
And with the same correction factor for that powder, the chronograph will match the QL prediction.

 

[Fred_C_Dobbs]

Look over QL's "Change Diagram" for your load and it's easy to see why even tiny differences at the start can make a substantial difference in the end.

Looking at my .308 Win load, the "usable case capacity" is 48.6 grains of water. Which means that the gunpowder starts off in a space of less than 0.2 cubic inches. When the primer goes BANG!, in less than one-half of one one-thousandth of a second, pressure drives the bullet about an inch and a half down the barrel, which increases the volume the powder is confined to by about 150%. And by that time the pressure has peaked, increasing about 3400-fold over the pressure I trapped inside that casing when I seated the bullet.

Shit's changing, real fast. Mind-bogglingly fast. And if you've ever studied the Ideal Gas Law, you know that the volume, temperature and pressure of a gas are interrelated. Which means tiny, almost microscopic differences between the dimensions of your real-world components and what QL has recorded in its db will make measurable differences at the chrono.

Measure everything you can measure with reasonable accuracy. To allow for human error, I take measurements from several different components and use the average value. More measurements, averaged, equals a lower error rate.

I find QL's bullet lengths almost always are wrong, but the dimensions it gives for the boattail almost always are right. I use a cheap 6x hand lens and regular dial calipers to measure my boattails.

Despite all my careful measuring of components, in the eight years I've been using it, QL's initial prediction has never once been within 20 fps of actual. That's when you have to start tweaking powder properties. Most of the time, my opening salvo is off well more than 20 fps so don't consider tweaking powder properties an option, consider it a necessity. QL is a tool, not a tutor. You da boss. Tweak it until it howls.

Here are the QL tweaking parameters I got from Chris Long, who created a load development process know as Optimum Barrel Time. OBT relies on QL's "barrel time" prediction, alternately known as "dwell," and effectively tweaking QL is integral to making OBT work as advertised.

My three main "tweaks" in QL are:

1.) Burn rate - no more than 5% higher or lower. More than that and I go to #2
2.) Weighting factor - no more than 10% change from QL default, else go to #3
3.) Bullet weight - this is a very good way to compensate for bore friction and other physical things that QL can't model. An increase in friction effectively reduces the accelerating force on the bullet, slowing it down. Increasing the bullet mass does the same thing in QL (F=MA). If you have to tweak this by more than a few single digit percentages, then there is something very weird going on. If things get too weird, reset it all to QL defaults, and start over with just the bullet weight and see what you get. I had one Savage 6mm barrel on a friends rifle that was really rough, and required a 3 grain increase in bullet weight (from 105 grains) to get the velocities to match. It was the only tweak that would let the model even get close to the right predictions.

The process is trial-and-error, tweaking these parameters until you can match at least two velocity measurements. I usually fire at least three different charge weights, from low to high, trying to bracket the expected OBT velocity range(s), and record velocity for each trial. It is best to fire 5 shots at each weight, if you have the patience, as the velocity average will be much more accurate than a single shot value. Single shots are OK to get you in the ballpark, but to get a good QL model, you need more than 1 at each charge weight. Then, tweak QL until you get the best match to your data samples.

You will find that it is very difficult, if not impossible to get an exact match for some component combinations. I am convinced that there are non-linear effects in the actual powder burn process that QL's linear system models do not encompass....

Those are the three key QL properties to tweak, but the order is not carved in stone. I know shooters who are successfully applying OBT who start by tweaking Weighting Factor, and still others who begin at Bullet Weight.

Two of the cardinal rules of QL are never to change anything unless you have a valid reason for doing so, and never change anything without a reasonable expectation that the change will produce a value that is more accurate than QL's default values would. QL has no end of values you can mess with, and it would be ridiculously easy to start tweaking aimlessly and find yourself lost in the weeds.

Also, one of QL's shortcomings is it fails to account for differences in primer brisance. I stole this formula from I forget who to adjust QL's starting pressure to make up for that shortcoming. It is not essential you use this, but I find it lessens the needed tweaking.

Shot Start (Initiation) Pressure = ( 1420 x bearing surface length ) + 2860

Throw in an additional 600 psi for 215M primers (which probably also goes for any magnum primer).
The bearing surface length is expressed in inches, i.e., 1" = 1.0; 1 1/8"= 1.125. Off the top of my head, I can't think of a single bullet manufacturer who publishes bearing surface length. And I wouldn't trust them if they did. So that's just another property for you to measure.

 

[nuclear_shooter]

Look over QL's "Change Diagram" for your load and it's easy to see why even tiny differences at the start can make a substantial difference in the end.

Looking at my .308 Win load, the "usable case capacity" is 48.6 grains of water. Which means that the gunpowder starts off in a space of less than 0.2 cubic inches. When the primer goes BANG!, in less than one-half of one one-thousandth of a second, pressure drives the bullet about an inch and a half down the barrel, which increases the volume the powder is confined to by about 150%. And by that time the pressure has peaked, increasing about 3400-fold over the pressure I trapped inside that casing when I seated the bullet.

Shit's changing, real fast. Mind-bogglingly fast. And if you've ever studied the Ideal Gas Law, you know that the volume, temperature and pressure of a gas are interrelated. Which means tiny, almost microscopic differences between the dimensions of your real-world components and what QL has recorded in its db will make measurable differences at the chrono.

Measure everything you can measure with reasonable accuracy. To allow for human error, I take measurements from several different components and use the average value. More measurements, averaged, equals a lower error rate.

I find QL's bullet lengths almost always are wrong, but the dimensions it gives for the boattail almost always are right. I use a cheap 6x hand lens and regular dial calipers to measure my boattails.

Despite all my careful measuring of components, in the eight years I've been using it, QL's initial prediction has never once been within 20 fps of actual. That's when you have to start tweaking powder properties. Most of the time, my opening salvo is off well more than 20 fps so don't consider tweaking powder properties an option, consider it a necessity. QL is a tool, not a tutor. You da boss. Tweak it until it howls.

Here are the QL tweaking parameters I got from Chris Long, who created a load development process know as Optimum Barrel Time. OBT relies on QL's "barrel time" prediction, alternately known as "dwell," and effectively tweaking QL is integral to making OBT work as advertised.



Those are the three key QL properties to tweak, but the order is not carved in stone. I know shooters who are successfully applying OBT who start by tweaking Weighting Factor, and still others who begin at Bullet Weight.

Two of the cardinal rules of QL are never to change anything unless you have a valid reason for doing so, and never change anything without a reasonable expectation that the change will produce a value that is more accurate than QL's default values would. QL has no end of values you can mess with, and it would be ridiculously easy to start tweaking aimlessly and find yourself lost in the weeds.

Also, one of QL's shortcomings is it fails to account for differences in primer brisance. I stole this formula from I forget who to adjust QL's starting pressure to make up for that shortcoming. It is not essential you use this, but I find it lessens the needed tweaking.

Shot Start (Initiation) Pressure = ( 1420 x bearing surface length ) + 2860

Throw in an additional 600 psi for 215M primers (which probably also goes for any magnum primer).
The bearing surface length is expressed in inches, i.e., 1" = 1.0; 1 1/8"= 1.125. Off the top of my head, I can't think of a single bullet manufacturer who publishes bearing surface length. And I wouldn't trust them if they did. So that's just another property for you to measure.

Good info here. I've been real busy preparing for a conference so I haven't gotten a chance to play around with this any since tweaking bullet length weight. I don't jam my bullets into the lands, but I only jump them a short way (0.010") which might also be causing my slower velocities. I will try playing with the start pressure next.