Does QuickLoad include Grendel?

[centerfire]

Centrefire,

I do believe you're onto something here.

Until now I have been messing with the Weighting Factor trying to match outputs with actual velocities, with no joy. Using your method however, if you vary the case capacity to match actual velocities it is almost like you are 'calibrating' the program. What JA is saying about the shorter case and bullet moving before the powder pressure starts to build then an artificially greater case capacity could go some way to being a QL velocity-predictor remedy.

As for chamber pressure... Without proper pressure testing we are left assuming that the pressure QL predicts is correct for the velocities it predicts. As we know it is almost impossible to attach a strain gauge on an AR directly over the chamber so I suppose we could match the velocities/pressures of powder and bullet manufacturer tables with what QL predicts. What you are doing, using case capacity as an independent variable and concentrating on matching predicted with actual velocities makes more sense to me than trying to measure pressure. I'm going to give that a go...Thanks for the heads-up.

Actually it's fairly easy to attach the strain gauge to an AR chamber. My HG comes off with two screws. With that said I only measured my final load development using A2520 and 107TMK. I have a rifle class coming up and needed to verify the load was safe, I wasn't confident in QL. I'm leaning back to my chronograph results because that is almost all of my testing/measuring and, frankly, I'm not very familiar with Pressure Trace (my friend ran it, it's his). What little I can tell you about it is that it matched my manipulated QL output far closer than QL's output with actual case capacity. This is all anecdotal at best but it is what I have observed. Take it for what it is worth.

[JASmith]

Actually it's fairly easy to attach the strain gauge to an AR chamber. My HG comes off with two screws. With that said I only measured my final load development using A2520 and 107TMK. I have a rifle class coming up and needed to verify the load was safe, I wasn't confident in QL. I'm leaning back to my chronograph results because that is almost all of my testing/measuring and, frankly, I'm not very familiar with Pressure Trace (my friend ran it, it's his). What little I can tell you about it is that it matched my manipulated QL output far closer than QL's output with actual case capacity. This is all anecdotal at best but it is what I have observed. Take it for what it is worth.

Post a picture of your gage set up.

Most ARs have threads over the chamber that extend to past the body of the Grendel. The threads make attaching the gage impossible, and, per the RSI literature, we need a bit of room between any change of diameter (threads count) and the gage.

[centerfire]

Post a picture of your gage set up.

Most ARs have threads over the chamber that extend to past the body of the Grendel. The threads make attaching the gage impossible, and, per the RSI literature, we need a bit of room between any change of diameter (threads count) and the gage.

I don't have pictures. The chamber of an AR starts about the last 1/3 of the extension and extends past the end of the receiver. The case is a little over 2" and there is enough room for the sensor without the HG on. I have a Proof CF barrel and there is plenty of steel shank visible.

[JASmith]

[grayfox]

I don't have pictures. The chamber of an AR starts about the last 1/3 of the extension and extends past the end of the receiver. The case is a little over 2" and there is enough room for the sensor without the HG on. I have a Proof CF barrel and there is plenty of steel shank visible.

CF, definitely not an expert, but your statement, 'The case is a little over 2" ' does make me wonder.......... I thought the case of the Grendel is 1.520" max. So does this refer to the overall length, COAL, as opposed to just the case? Guess I would also offer that the bullet (part of the COAL measurement) often sticks into the barrel portion? Finally, in the Saami pdf spec, the maximum chamber dimension shown on the sheet (which is indicated as a "Reference dimension") is 1.8113". So I think the statement regarding '...a little over 2" ' deserves some clarification.

edit to add, if you have some data, that's great. I just don't see the accuracy of the 2 inches statement...

[centerfire]

I tried a large number pf powder and bullet combinations and found that I could find NO, NADA, ZILCH, user settable QL parameter that could be transferred from one powder to another in QuickLoad.

That's true. I'm sitting in a hotel room and going from memory but I settled on 37gr of water generically from the original 35.8 (I think, I'll check this weekend when I'm home). For A2520, 37.8 grain gets predicted MV closer to actual MV. PT recorded pressure under 48K for 31gr of A2520 but the system is not known to be very precise from what I understand. Either way, QL predicted my load (107TMK and 31gr of A2520) to be almost 2700fps and 53K to 54K PSI. My actual results were low 2600fps. That is a fairly high discrepancy regardless of individual barrel quirks.

BTW, I said 25% error above and that is not correct. I'm not sure where I got that from. On average the error I see with the software for the cartridge is 75fps to 100fps. That's obviously less than 25%. However, for a cartridge like Grendel 100fps is the difference between a safe load and a dangerous load.

[centerfire]

CF, definitely not an expert, but your statement, 'The case is a little over 2" ' does make me wonder.......... I thought the case of the Grendel is 1.520" max. So does this refer to the overall length, COAL, as opposed to just the case? Guess I would also offer that the bullet (part of the COAL measurement) often sticks into the barrel portion? Finally, in the Saami pdf spec, the maximum chamber dimension shown on the sheet (which is indicated as a "Reference dimension") is 1.8113". So I think the statement regarding '...a little over 2" ' deserves some clarification.

edit to add, if you have some data, that's great. I just don't see the accuracy of the 2 inches statement...

Yes, sorry. Cartridge length.

[LRRPF52]

The location of the AR15 barrel extension flange makes gauge placement impossible with 6.5 Grendel on a standard AR15/Grendel barrel.

If you place the gauge forward of the flange, you won't get readings directly over the center of the propellant column, and thus will not get a peak pressure reading.

[JASmith]

That is a very nice cross section of a standard pressure barrel for either copper or piezo gages!

The port is the same distance from the base of the case where one should glue a strain gage on the outside of the barrel.

[centerfire]

The location of the AR15 barrel extension flange makes gauge placement impossible with 6.5 Grendel on a standard AR15/Grendel barrel.

If you place the gauge forward of the flange, you won't get readings directly over the center of the propellant column, and thus will not get a peak pressure reading.

Dunno what to tell you, numbers came out of the wizard box. I had to go read the Pressure Trace site but it does discuss placing the sensor over the throat and what the resulting data looks like. Frankly it's not especially important to me, I'm not a scientist doing lab work or writing a study. It's all anecdotal and every chronograph reading (or the PT) is diagnostic in nature anyway. This discussion centered around QL not pressure testing and I don't feel like I conducted a test. I certainly don't think I've presented it that way either. If you feel like any information I've provided is erroneous you're free to dismiss it.

[LRRPF52]

Dunno what to tell you, numbers came out of the wizard box. I had to go read the Pressure Trace site but it does discuss placing the sensor over the throat and what the resulting data looks like. Frankly it's not especially important to me, I'm not a scientist doing lab work or writing a study. It's all anecdotal and every chronograph reading (or the PT) is diagnostic in nature anyway. This discussion centered around QL not pressure testing and I don't feel like I conducted a test. I certainly don't think I've presented it that way either. If you feel like any information I've provided is erroneous you're free to dismiss it.

My post was meant to address the challenges of gauge placement on the AR15, not a critique of anyone. I think the common denominator everyone is focused on here is pressure measurement.

The thread started off focused on the accuracy of Quick Load when trying to predict internal ballistics with 6.5 Grendel.

Pressure trace and chronographs were mentioned, which helps add depth and breadth following critical thinking standards.

I actually appreciate the more technical nature of what you posted so far.

[kmon]

On the bullet being started by the primer, we all use Magnum or hot primers for our AR Grendels and the extra energy from the magnum primers does provide more energy to unseat the bullet than a standard primer. If there was a standard primer that had the cup thickness needed would be perhaps nice then again with the performance we get from the Grendel why mess with it.

Now in some other cartridges that are also short you can see a big difference in consistency, accuracy and much lower extreme spreads. One example is the 22 Hornet, though it is a very small rifle cartridge it burns pistol powder and not much of it and the standard pistol primers will give much better consistency. Some others are 218 bee, 25-20 and 32-20 to name a few. All short cases and yes i do load and shoot those. Another area that the pistol primers work well with is subsonic loads in rifle cartridges to get your powder burning well before the bullet is unseated from the case gives better consistency.

I know this is off topic but a post above reminded me of this

[Jimla]

By increasing case capacity I reduced predicted velocity and chamber pressure simultaneously. It's not perfect but I found that of the 10 or so different powders I chronographed my method seemed to have narrowed the error similar to my observed results and predictions of other cartridges I have also chronographed.

I did some Quick Load Experiments with three loads measure this week.

Load One: 123 SST with CFE223
Using the Default(No adjustment) max safe load calculated at 2492 fps
Using Burn Rate to Match Velocity, max safe load calculated at 2492 fps
Using case capacity to Match Velocity, max safe load calculated at 2473 fps

Load two: 123 SST with IMR 8208 XBR
Using the Default(No adjustment) max safe load calculated at 2425 fps
Using Burn Rate to Match Velocity, max safe load calculated at 2431 fps
Using case capacity to Match Velocity, max safe load calculated at 2457 fps

Load three: 90 TNT with IMR 8208 XBR
Using the Default(No adjustment) max safe load calculated at 2850 fps
Using Burn Rate to Mach Velocity, max safe load calculated at 2853 fps
Using case capacity to Mach Velocity, max safe load calculated at 2887 fps

If you notice the max safe load is within about 1% from each other, looking at velocity alone may be useful for finding max safe loads velocities before firing a single shot.

[Klem]

Jimla,

I am trying to understand what you are doing or have discovered here. I might be missing something in your detail.

My understanding is that the OP is concerned with the degree of confidence we have that QL predicts reality in this calibre. Across the forum confidence varies but that there is a general consensus that QL is useful but not perfect. The lack of confidence is because its predictions of velocity don't precisely match our chronographs. Plus individuals have different expectations of how close a match between computer prediction and reality is reasonable, given differences in ambient temperature, barrels, and chronographs will always produce differences between the program and the chronograph.

Centrefire is saying that a fix he uses is varying the case capacity until the velocity predicted by QL matches the velocity he gets from his chronograph. Once that is done then the program is 'calibrated' and presumably from then on, varying other variables like amount of powder and COAL will lead to better predictions of velocity.

Without the ability to detect pressure in an AR at a consumer level if we can at least get velocity to be more accurately predicted then hopefully the pressure prediction that goes with it will also be more precise. A pressure gauge on a Grendel bolt gun would be helpful but no-one has done that yet.

[Jimla]

Jimla,

I am trying to understand what you are doing or have discovered here. I might be missing something in your detail.

My understanding is that the OP is concerned with the degree of confidence we have that QL predicts reality in this calibre. Across the forum confidence varies but that there is a general consensus that QL is useful but not perfect. The lack of confidence is because its predictions of velocity don't precisely match our chronographs. Plus individuals have different expectations of how close a match between computer prediction and reality is reasonable, given differences in ambient temperature, barrels, and chronographs will always produce differences between the program and the chronograph.

Centrefire is saying that a fix he uses is varying the case capacity until the velocity predicted by QL matches the velocity he gets from his chronograph. Once that is done then the program is 'calibrated' and presumably from then on, varying other variables like amount of powder and COAL will lead to better predictions of velocity.

Without the ability to detect pressure in an AR at a consumer level if we can at least get velocity to be more accurately predicted then hopefully the pressure prediction that goes with it will also be more precise. A pressure gauge on a Grendel bolt gun would be helpful but no-one has done that yet.