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Old June 13, 2019, 03:43 PM   #51
Aguila Blanca
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Since you're here, Barney, I'll just comment that I have downloaded the program and I like the look of it, but I load using Winchester and Hodgdon powders only. In order for me to add Winchester 231 to the propellant database requires that I have data that's not available to mere mortals. Consequently, regardless of how nice the program looks, it simply isn't of any practical use.

As I posted above, I attempted two runs with GRT, using two powders in your database that straddle Winchester 231 on Hodgdon's burning rate chart. All three are near the top of the chart, so I expected that by averaging the results of those two runs, I should be fairly close to my actual chronograph results.

The GRT results weren't in the same universe.
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Old June 13, 2019, 04:35 PM   #52
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Aguilla Blanca,

you're right. This isn't anything you or we can fix with the required precision by looking at charts or "guesstimating".

Maybe - try to import the QL-Powder file for the propellant and check once more...

Barney
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Old June 13, 2019, 05:26 PM   #53
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Quote:
Originally Posted by hounddawg View Post
As long as I use standard bullets and powders and stick to manufacturers recipes do I really need something like this? I know some of you shoot some pretty exotic cartridges where load data is scarce or non existent but for someone like me that colors inside the lines would this be helpful ?
Ditto from the other end.

I make custom projectiles by casting & swaging so there's zero chance they'd have anything I'd be interested in being literally not on the charts at all......

When I posted my concerns above I hoped to get people to think that this software is by NO means total & complete. There are other variables.
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Old June 13, 2019, 07:53 PM   #54
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Quote:
Originally Posted by BEG
Maybe - try to import the QL-Powder file for the propellant and check once more...
I don't have QuickLoad. UncleNick was kind enough to look up the powder properties for Winchester 231 in his QL for me (it's in a post in this discussion), but the QL data don't include a value for z2, and without a value for z2 GRT won't allow me to enter a new propellant into the database. That's why you'll see a couple or three posts above speculating on what the value of z2 should be.

So,, as a general comment on the program -- you can't advise people to import data from Quickload if Quickload doesn't provide values for all the parameters you ask for.
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Old June 13, 2019, 08:37 PM   #55
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I have now run GRT using the value for z2 of 0.9, as suggested. That allowed me to add Winchester 231 to the propellant database. I load two .45 ACP loads, one using Berry's 230-gr plated round nose bullets, and the other using Berry's 185-gr plated round nose, hollow-base bullets. I ran both through GRT, and for both the results were far higher velocity than what I actually saw.

The 230-gr load was chronographed long before I started trying to keep any sort of records, so all I remember was that the velocity was in the upper 700s. (BEG, that's obviously feet-per-second.) GRT says that this load will generate a velocity of 859.58 fps.

I started loading the 185-gr bullet more recently, so I do have a record of my velocity with that one. Even better, I've found two articles on the internet discussing that exact load (right down to the same bullet, same powder, and about the same charge). So we have some hard data to use for comparison.

With Berry's 185-gr projectile, a seating depth of 1.250", and a charge weight of 5.3 grains, GRT says I should see a velocity of 849.74 fps. My results averaged (three separate strings of five shots each) 671 fps.

What do other people say? Source number 1 used a C.O.L. of 1.240 (shorter than mine) and a charge weight of 5.4 grains of Win 231, and he reported a velocity of 817 fps.

Source number 2, which was published in Shooting Times magazine, also used a C.O.L. of 1.240 (I used 1.250). For a charge of 5.3 grains he recorded a velocity of 687 fps. That tells me that my results are consistent with his.

Source number 2 also did a couple of heavier charges. 5.7 grains yielded a velocity of 762 fps, and a charge of 6.1 grains yielded a velocity of 812 fps. Even this result is significantly below the GRT calculated velocity of 849.74 fps for 5.3 grains.

Obviously, something is off. It may well be the missing value for z2, but tinkering with such is far above my pay grade. At this point, I am just reporting real world results for those of you who know enough to be able to tinker with these things.

I did demonstrate one thing, though. In my opening post I mentioned that I tried to approximate results for Winchester 231 by choosing two powders in the GRT database that straddled 231 in Hodgdon's burn rate chart. If the z2 value of 0.9 is valid, then that approach did work. The results for N320 and N330 were 896 fps and 849 fps. (For the 230-grain bullet.) The results for Winchester 231 were 860 fps, which does slot nicely between 896 and 849.

Unfortunately, all those numbers are much too high ...
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Old June 14, 2019, 01:24 AM   #56
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Barney, thanks for joining the discussion.

I’m seeing different output values in the results text area than what is shown in the graph below the text. For instance, using input data directly from the GRT database for:
9mm Luger
Hornady HP/XTP 35540, 0.355, 115 grain
Vihtavuori N320 (2018-12) (I manually entered 4.5 grains)

the results text shows:
maximum pressure 29255 psi
Muzzle velocity 1141 ft/s,

However, the pressure curve in the graph peaks at about 23,000 psi on the vertical scale to the left, but if you put your cursor on the peak, a popup window shows 26625 psi. The velocity curve shows MV to be about 950 ft/s on the vertical scale to the right, but if you put the cursor on it, the popup window shows 1139 ft/s. Shouldn’t the popup values and the scales agree, or am I misinterpreting something?
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Old June 14, 2019, 01:36 AM   #57
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Aguilla Blanca,

as you mentioned, there are noumerous factors, which might affect the simulation to be "faster" than observed. One is for sure to have the appropriate powder behaviour and that is more, than just z2. Given the fact, GRT currently simulates pressures and bullet speeds up to +-5% accuracy or better, with known powders, I tend to belive this is the main reason for the deviation of apx. 20%, you observe. But on the other hand - it could be something else... . But to approach other reasons, we would have to rule out error no1 and this simply isn't possible yet.

I have the impression, you're a experinenced handloader, and obviously do measurements on the seating depth and OAL of your bullets. So this should mean no offense, but I experience this the most common reason, why GRTs results are somewhat out of range with reality, if everything else is correct. Have you personally measured the cases volume, you have entered into GRT? If the case volume would be actually larger by "only" 5-6%, this will easily generate a recognizable drop in V0. Of course this surely would not deliver a sufficient explanation for the 178fps deviation, but it could narrow the gap, if excluded from the list of possible errors.

Please feel free to attach the .grtload to a ticket on: www.grtools.de. More proficient folks (than me) will have a look at it.

Cheers...
Barney

Last edited by BEG; June 14, 2019 at 05:35 AM.
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Old June 14, 2019, 01:45 AM   #58
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higgite,

you discovered a bug which was reported by other sources, as well. It will be fixed in the next release comming over the weekend or early next week.

Thanks...
Barney
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Old June 14, 2019, 02:08 AM   #59
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Quote:
Originally Posted by BEG
I have the impression, you're a experinenced handloader, and obviously do measurements on the seating depth and OAL of your bullets. So this should mean no offense, but I experience this the most common reason, why GRTs results are somewhat out of range with reality, if everything else is correct. Have you personally measured the cases volume, you have entered into GRT? If the case volume would be actually larger by "only" 5-6%, this will easily generate a recognizable drop in V0. Of course this surely would not deliver a sufficient explanation for the 178fps deviation, but it could narrow the gap, if excluded from the list of possible errors.
I have not measured the case volume -- I accepted the default. I'll see what I can do about getting my own reading.
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Old June 14, 2019, 05:39 AM   #60
BEG
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Quote:
I have not measured the case volume...
You should! You should as well measure the length and actual weight of your bullets. Just to be sure, you're in the ballpark with what you entered into the simulation.

There is also a friction coefficient and the initial pressure value, which should be "tweaked" if certain custom bullets are used.

Hope this helps...
Barney

Last edited by BEG; June 14, 2019 at 05:46 AM.
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Old June 14, 2019, 12:37 PM   #61
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Bullet length and weight is something I've checked. I have submitted bullet dimensional data for the Berry's bullets I use and for a number of other projectiles through the GRT ticket system. I have found Berry's bullets to be acceptably consistent with regard to weight. I might be fussier if I were a bullseye competitor, but ... I'm not.
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Old June 14, 2019, 02:30 PM   #62
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Downloaded the software and tried it on a few loads that I did with N135 powder. The simulated muzzle velocities are within a few percent from what I measured. Too bad the powder library is limited. I can see why the propellent manufacturers not eager to disclose the information. That may be why quickload is doing it themselves. I agree it is unfair, to quickload and users who have paid, to port over the powder data.

-TL

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Old June 15, 2019, 11:32 AM   #63
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I don't have a problem with porting from my copy of QL to my copy of GRT. Since I've paid the license fees for QL and upgrades for about 20 years, I figure this is no worse than getting a second opinion. Also, publishing an occasional piece of information is something NECO's Ed Dillon (U.S. QL distributor) has said is OK as I think he feels it encourages people to buy the program. However, spreading the QL data around wholesale to those who haven't bought into it becomes an IP rights violation.

I've found with QL it is pretty common for case volumes to be minimum for cases I've seen. That produces errors on the high side of pressure to discourage loading too warm. For pistol cases, though, I almost automatically add a grain of case water overflow capacity as I've found that to be pretty close with .45 Auto, .38 Special and .357 Magnum among others. With rifle cases, like .308 Win, it can be one to three grains low, depending on the make of the case. Also, keep in mind that for brass being fired at peak pressures below about 30,000 psi, you want to use the resized case capacity. For those above 40,000 psi, you want to use the as-fired capacity. Between those two numbers it varies with the cartridge as to whether resized or as-fired capacity will give you the most realistic results and you just want to compare your prediction with a maximum published charge to the velocity and pressure reported by the powder maker (who usually is the only one with average performing data powder for load development and testing).
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Old June 30, 2019, 08:22 PM   #64
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When playing with the bullet types, I noticed the tool predicted cast bullet having higher friction than jacketed bullet.

My experience is quite on the contrary. Cast bullets (lubricated of course) have the least friction, followed by jacketed. The worst is plated.

Do you see the same with the loads you have tested? What does quickload have to say? Anybody has entered a ticket for plated bullets? Thanks.

-TL

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Old June 30, 2019, 09:13 PM   #65
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QuickLOAD uses a lower start pressure on lead than on jacketed bullets. This results in lower peak pressure as the bullet is further down the tube when the pressure peaks and therefore has a greater volume behind it for the gas to fill. It also puts a lower limit on bore friction.
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Old June 30, 2019, 09:35 PM   #66
tangolima
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In GRT, the bullet types (jacket, cast, etc) seem to change friction only. The initial pressure is determined by firearm type (pistol, rifle, etc). Cast bullets having more friction than jacketed does seem right though.

-TL

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