JimGnitecki
Member
- Joined
- Mar 28, 2010
- Messages
- 1,258
Comparison of QuickLOAD versus GRT simulations for an unusual 9mm pistol loading
Background of this comparison:
I have both the QuickLOAD (hereafter “QL”) and the Gordons Reloading Tool (hereafter “GRT”) simulation software packages, and used them the other day to compare their predicted results for an unusual 9mm pistol loading.
The results were “similar” but different than the “actual”, and also had enough differences in them to make me ask (a) why? and (b) are the differences typical for simulations?
I should mention right now that while I have decades of reloading experience, I am “new” to using simulation software. I bought QL and downloaded the most current free beta version of GRT, both within the past week. I am very early in my learning on both of them, and may well not be doing things correctly, or maybe just not making adjustments to the default software assumptions that an experienced user might know to make.
Also, the load I was developing is unusual. I want a fairly fast and very accurate 9mm 115 grain pistol load (1300 to 1350 fps ideally). Based on many years of successful usage, I prefer Vihtavuori powders. I also want to use the Hornady HAP 115g jacketed hollow point bullet, which is the same as the Hornady XTP bullet except the HAP’s hollow point does not have the “cuts” in it that promote expansion, as the HAP is designed for Action Pistol competition where no chance of a misfeed can be tolerated.
The Vihtavuori load table for 9mm shows the following data for a combination of bullet and powder that comes very close to meeting my objectives:
Caliber 9mm
OAL = 1.142”
Primer = Small Pistol
Case brand = Lapua
Powder = Vihatvuori 3N38 with minimum = 7.2 grains and maximum = 8.7 grains (compressed)
Muzzle velocity out of a 4” barrel supposedly was 1181 fps at 7.2g and 1401 fps at 8.7 grains.
Bullet = Berry´s 115g HB RN TP
This load implies that about 8.0 grains might deliver a bit over 1300 fps. I communicated with a well known ballistics author who did some QL simulations on this load, and assured me that substituting the HAP bullet for the Berry’s should produce lower pressure than the Berry’s load since the HAP bullet is shorter than the Berry’s bullet. Thus if I use the same OAL, the max pressure should be lower.
Note that this load uses VV 3N38 powder, which is a slow burning pistol powder. VV recommends it to Action Pistol competitors who need high velocity AND enough residual gas pressure past the muzzle to effectively operate a compensator. A slow burning powder can achieve both objectives by limiting peak pressure while still generating enough bullet velocity in the barrel, and enough gas velocity beyond the muzzle to operate the compensator.
Before I ever got QL and GRT, I had already tested the load at 7.2, 7.4, 7.6, 7.8, and 8.0 grains. The 7.2 grain load was not good. The 7.4 through 7.8 grain loads produced gradually improving accuracy. The 8.0 grain loading produced the best accuracy, and also the highest velocity at 1324 fps. Its Standard Deviation was just 10.0. The best 5-shot group at 25 yards, off a suboptimal sandbag and with my 70 year old eyes looking through progressive bifocals, was 1-3/8” but the best 4 in that group were just 13/16” (0.81”). This was fired out of my unmodified SIG P210 American Target pistol. Note that the 8.0 grain load is almost exactly between the minimum and maximum loads in the VV load table, for the 115g bullet and 3N38 powder. So, it’s not “hot” and not “weak” either.
Note that since the max load VV recommended was 8.7 grains, it would be logical to assume that that loading either hit, or was close to, either the SAAMI or CIP limit of around 34,000 psi. So I figured that at 1324 fps versus the 1401 fps shown for the 8.7g load, my load must be somewhere under 34,000 psi but not too far below since 1324 is not that far from 1401 fps.
So, already knowing I had a good (maybe even great) load, but curious about what peak pressure I was producing to get it, I ordered QL and then found out about the free beta GRT and downloaded that too.
In dojng the required inputs, I entered my actuals, wherever i had them, in place of the default values. That means that I used my actual (Hornady) case internal volume, my actual case height, my actual bullet length, actuaL OAL, etc. Then, I ran the simulation for each software package.
My Results:
The key differences that I, as an “amateur” in using simulation software, detected in the two results were:
Item / QL / GRT / abs diff / % diff / Actual (if available)
Max pressure / 22,972 psi / 25,181 / QL 2209 lower / QL 9.6% lower
Muzzle velocity / 1185 fps / 1249 fps / QL 64 lower / QL 5.4% lower / 1324 fps actual
Barrel time (10% Pmax to muzzle) / .552 ms / .5295 ms / QL .0225 ms higher / QL 4.2% higher
Percent of propellant burned / 75.49% / 70.3% / QL 5.2% higher / QL 7.4% higher
Ballistic efficiency / 23.5% / 26% / QL 2.5% lower / QL 10.6% lower
Load ratio / 98.7% / 101.8% / QL 3.1% lower / QL 3.1% lower
Questions prompted by looking at these differences one at a time:
Max Pressure:
Note that the max pressures differ by 9.6%.
- Is this typical for simulations, or is it because this is an unusual pistol load that only burns 70 to 75% of the powder before the bullet leaves the muzzle?
-Does this 23k to 25k psi pressure, compared to the SAMMI max for 9mm of 34,000 psi, surprise any of you more experienced simulation users? After all, with an actual velocity = 1324 fps, this IS a reasonably hot load for 9mm.
Muzzle Velocity:
Note that there is a 5.4% difference predicted by the 2 simulations.
Note also that the actual velocity (measured accurately by Labradar) is almost 9% higher than the average of the 2 simulations!
- Why?
Barrel Time (10% Pmax to muzzle):
There is a 4.2% difference between the 2 simulations.
Percent of propellant burned:
There is a 7.4% difference in the amount of propellant burned.
- Both of the simulations show a relatively low 70 to 75% burn. Is this because this is an unusual load with a slow powder designed to feed a pistol compensator lots of gas after the bullet has left the muzzle?
Ballistic efficiency:
Is the Ballistic efficiency simulation, either 23.5% or 26%, typical? Or is it low due to the unusual load?
Load ratio:
The Load ratio (i.e. percent of the available volume left in the case below the bullet that is actually used by the powder with this load) shows as 98.7% in QL and 101.8% in GRT. This correctly says that this 8.0 grains of VV 3N38 powder requires near or slightly over the available case volume under the bullet. i.e. it is near or actually a very slightly compressed load.
But, given that I did not use the “default” internal volume for a 9mm case with either QL or GRT, but instead carefully measured the ACTUAL volume via the “grains of water” test, this SHOULD have been exactly the same volume with both simulations.
The fact that it is not the same means that QL and GRT use slightly different powder density. Indeed, QL says it used a solid density of 1.51 g/cc, while GRT says it used the same value. So why is the load ratio different?
I am trying hard to learn how to properly use QL and GRT, and I would greatly appreciate it if some of you experienced load simulators could give me some guidance as to how to get my simulations closer to the actual results I get when I shoot the loads.
ANY help or advice would be appreciated.
I have attached screenshots for both QL and GRT showing my inputs and the results.
Jim G
Background of this comparison:
I have both the QuickLOAD (hereafter “QL”) and the Gordons Reloading Tool (hereafter “GRT”) simulation software packages, and used them the other day to compare their predicted results for an unusual 9mm pistol loading.
The results were “similar” but different than the “actual”, and also had enough differences in them to make me ask (a) why? and (b) are the differences typical for simulations?
I should mention right now that while I have decades of reloading experience, I am “new” to using simulation software. I bought QL and downloaded the most current free beta version of GRT, both within the past week. I am very early in my learning on both of them, and may well not be doing things correctly, or maybe just not making adjustments to the default software assumptions that an experienced user might know to make.
Also, the load I was developing is unusual. I want a fairly fast and very accurate 9mm 115 grain pistol load (1300 to 1350 fps ideally). Based on many years of successful usage, I prefer Vihtavuori powders. I also want to use the Hornady HAP 115g jacketed hollow point bullet, which is the same as the Hornady XTP bullet except the HAP’s hollow point does not have the “cuts” in it that promote expansion, as the HAP is designed for Action Pistol competition where no chance of a misfeed can be tolerated.
The Vihtavuori load table for 9mm shows the following data for a combination of bullet and powder that comes very close to meeting my objectives:
Caliber 9mm
OAL = 1.142”
Primer = Small Pistol
Case brand = Lapua
Powder = Vihatvuori 3N38 with minimum = 7.2 grains and maximum = 8.7 grains (compressed)
Muzzle velocity out of a 4” barrel supposedly was 1181 fps at 7.2g and 1401 fps at 8.7 grains.
Bullet = Berry´s 115g HB RN TP
This load implies that about 8.0 grains might deliver a bit over 1300 fps. I communicated with a well known ballistics author who did some QL simulations on this load, and assured me that substituting the HAP bullet for the Berry’s should produce lower pressure than the Berry’s load since the HAP bullet is shorter than the Berry’s bullet. Thus if I use the same OAL, the max pressure should be lower.
Note that this load uses VV 3N38 powder, which is a slow burning pistol powder. VV recommends it to Action Pistol competitors who need high velocity AND enough residual gas pressure past the muzzle to effectively operate a compensator. A slow burning powder can achieve both objectives by limiting peak pressure while still generating enough bullet velocity in the barrel, and enough gas velocity beyond the muzzle to operate the compensator.
Before I ever got QL and GRT, I had already tested the load at 7.2, 7.4, 7.6, 7.8, and 8.0 grains. The 7.2 grain load was not good. The 7.4 through 7.8 grain loads produced gradually improving accuracy. The 8.0 grain loading produced the best accuracy, and also the highest velocity at 1324 fps. Its Standard Deviation was just 10.0. The best 5-shot group at 25 yards, off a suboptimal sandbag and with my 70 year old eyes looking through progressive bifocals, was 1-3/8” but the best 4 in that group were just 13/16” (0.81”). This was fired out of my unmodified SIG P210 American Target pistol. Note that the 8.0 grain load is almost exactly between the minimum and maximum loads in the VV load table, for the 115g bullet and 3N38 powder. So, it’s not “hot” and not “weak” either.
Note that since the max load VV recommended was 8.7 grains, it would be logical to assume that that loading either hit, or was close to, either the SAAMI or CIP limit of around 34,000 psi. So I figured that at 1324 fps versus the 1401 fps shown for the 8.7g load, my load must be somewhere under 34,000 psi but not too far below since 1324 is not that far from 1401 fps.
So, already knowing I had a good (maybe even great) load, but curious about what peak pressure I was producing to get it, I ordered QL and then found out about the free beta GRT and downloaded that too.
In dojng the required inputs, I entered my actuals, wherever i had them, in place of the default values. That means that I used my actual (Hornady) case internal volume, my actual case height, my actual bullet length, actuaL OAL, etc. Then, I ran the simulation for each software package.
My Results:
The key differences that I, as an “amateur” in using simulation software, detected in the two results were:
Item / QL / GRT / abs diff / % diff / Actual (if available)
Max pressure / 22,972 psi / 25,181 / QL 2209 lower / QL 9.6% lower
Muzzle velocity / 1185 fps / 1249 fps / QL 64 lower / QL 5.4% lower / 1324 fps actual
Barrel time (10% Pmax to muzzle) / .552 ms / .5295 ms / QL .0225 ms higher / QL 4.2% higher
Percent of propellant burned / 75.49% / 70.3% / QL 5.2% higher / QL 7.4% higher
Ballistic efficiency / 23.5% / 26% / QL 2.5% lower / QL 10.6% lower
Load ratio / 98.7% / 101.8% / QL 3.1% lower / QL 3.1% lower
Questions prompted by looking at these differences one at a time:
Max Pressure:
Note that the max pressures differ by 9.6%.
- Is this typical for simulations, or is it because this is an unusual pistol load that only burns 70 to 75% of the powder before the bullet leaves the muzzle?
-Does this 23k to 25k psi pressure, compared to the SAMMI max for 9mm of 34,000 psi, surprise any of you more experienced simulation users? After all, with an actual velocity = 1324 fps, this IS a reasonably hot load for 9mm.
Muzzle Velocity:
Note that there is a 5.4% difference predicted by the 2 simulations.
Note also that the actual velocity (measured accurately by Labradar) is almost 9% higher than the average of the 2 simulations!
- Why?
Barrel Time (10% Pmax to muzzle):
There is a 4.2% difference between the 2 simulations.
Percent of propellant burned:
There is a 7.4% difference in the amount of propellant burned.
- Both of the simulations show a relatively low 70 to 75% burn. Is this because this is an unusual load with a slow powder designed to feed a pistol compensator lots of gas after the bullet has left the muzzle?
Ballistic efficiency:
Is the Ballistic efficiency simulation, either 23.5% or 26%, typical? Or is it low due to the unusual load?
Load ratio:
The Load ratio (i.e. percent of the available volume left in the case below the bullet that is actually used by the powder with this load) shows as 98.7% in QL and 101.8% in GRT. This correctly says that this 8.0 grains of VV 3N38 powder requires near or slightly over the available case volume under the bullet. i.e. it is near or actually a very slightly compressed load.
But, given that I did not use the “default” internal volume for a 9mm case with either QL or GRT, but instead carefully measured the ACTUAL volume via the “grains of water” test, this SHOULD have been exactly the same volume with both simulations.
The fact that it is not the same means that QL and GRT use slightly different powder density. Indeed, QL says it used a solid density of 1.51 g/cc, while GRT says it used the same value. So why is the load ratio different?
I am trying hard to learn how to properly use QL and GRT, and I would greatly appreciate it if some of you experienced load simulators could give me some guidance as to how to get my simulations closer to the actual results I get when I shoot the loads.
ANY help or advice would be appreciated.
I have attached screenshots for both QL and GRT showing my inputs and the results.
Jim G