Does QuickLoad include Grendel?

[daved20319]

And if it does, what's the Hordes opinion of its accuracy? Up to now, I've always worked with cartridges that were well established, but the Grendel, not so much, we're still learning what can be done with it. And what's more, the vast majority of info out there is for AR based Grendels, but I'm running a bolt gun, so in theory, at least, I should be able to tolerate more pressure. Appreciate your thoughts on the subject, thanks.

Dave

[grayfox]

Dave,
There are several threads on here already about using Quickload for the Grendel by those who do use it.
And btw, I don't know what you mean by "well established... not so much" for the Grendel. That seems to be a vaguely-undefined ding without any objective measure behind it, no offense.

There are also threads about using a bolt gun, in fact a subsection devoted to the bolt-flavor in Grendel.
Have you done any searching out yet to see what info is already present to educate yourself?

I shoot both AR style and bolt style, do not use QL (and have not seen any need to personally) but have no issues with those that do, to each his own toolset!

R/

[Klem]

Dave,

Yes, QL has Grendel. I use it, it works for me and across all the calibres I am interested in.

How accurate is it? It's conservative in the pressure sense and the predicted MV will never be absolutely precise, but neither will manufacturer tables given different ambient temperatures and barrel lengths/types. It's a computer simulation, a simplification of reality. If you take the time to enter actual data instead of relying on the defaults it is more accurate. It also gives you peace of mind, lets you try differences in powders, bullets and seating depths without spending money. It doesn't replace range time but it will narrow down the possibilities.

It lags behind all the latest bullet releases (e.g. Sierra Tipped Match Kings and Game Changer). It does however let you input the dimensions of these new bullets into its library.

As for bolt gun over-pressure, sure you can load over SAAMI max in a bolt gun and reasonably expect it to tolerate more than an AR15. But why would you do this? Just get a larger 6.5 calibre and underload it. The gun will weigh the same as a Grendel and as long as you fill at least 80% of the available case with powder (QL will tell you this) you can mimic a 'hot' Grendel without the wear-and-tear on gun and brass. Plus you can load normally and enjoy the longer range.

[grayfox]

I got a 2d 6.5 CM for some 123's for doing with it just as Klem says...!!! just enough to be a sweet but fast (in Grrr terms) bullet...
no worries.

[kmon]

it works, at one time the pressures showed high for Grendel but think that might have been resolved with later releases, not sure on that though. I like the quickloads program and like Klem said you can get pretty accurate results with it, mostly I got it for some older cartridges and wildcats that there was very little data for but use it for other rounds and what ifs that arise.

[centerfire]

it works, at one time the pressures showed high for Grendel but think that might have been resolved with later releases, not sure on that though. I like the quickloads program and like Klem said you can get pretty accurate results with it, mostly I got it for some older cartridges and wildcats that there was very little data for but use it for other rounds and what ifs that arise.

At this point I've chronographed a handful of different cartridges using QL and based on my measured results I don't think QL has fixed the high pressure predictions for Grendel.

[Klem]

At this point I've chronographed a handful of different cartridges using QL and based on my measured results I don't think QL has fixed the high pressure predictions for Grendel.

This is a bold and damning statement...What are you referring to here?

'Fixed' assumes something was/is incorrect. In this case you refer to 'high pressure' (peak pressure). You are using muzzle velocity as a proxy for muzzle pressure, yes? And muzzle pressure as an indicator of peak pressure? Can I ask how you have come about this conclusion based on chronograph results and what are you comparing them against?

[centerfire]

This is a bold and damning statement...What are you referring to here?

'Fixed' assumes something was/is incorrect. In this case you refer to 'high pressure' (peak pressure). You are using muzzle velocity as a proxy for muzzle pressure, yes? And muzzle pressure as an indicator of peak pressure? Can I ask how you have come about this conclusion based on chronograph results and what are you comparing them against?

No, a strain gage and chronograph combined. There's nothing bold about my statement, I noticed a roughly 25% difference between predicted MV and recorded velocity so my buddy brought out his Pressure Trace. It's why I adjust case capacity instead of weighting factor. I've measured a few other cartridges too and none of them have the same error that Grendel does.

ETA: I misstated 25%. It should be 75fps to 100fps.

[JASmith]

No, a strain gage and chronograph combined. There's nothing bold about my statement, I noticed a roughly 25% difference between predicted MV and recorded velocity so my buddy brought out his Pressure Trace. It's why I adjust case capacity instead of weighting factor. I've measured a few other cartridges too and none of them have the same error that Grendel does.

That was my experience too. The pressures for some powders were way off, but one or two weren't bad.

I did, however, discover that the correction factors for velocity and pressure were the same percentage over the entire range of powder weights one would consider.

A Western Powders ballistician explained that the case is short enough that the primer discharge hits the base of the bullet and gets it moving before the charge lights off. That means that the bullet is moving when the powder starts merrily burning. The result is the case volume is changed and the initial velocity is not zero.

While repeatable as demonstrated by the fine accuracy, it is not predicable with the physics models used in QuickLoad.

I have not had an opportunity to see if we get similar results in other short cases like the BR series and the WSSM series.

[Klem]

OK, this is getting interesting...A pressure trace like Recreational Software Incorporated sells?

Is the pressure trace indicating higher or lower by 25% than QL?

What changes do you make to case volume to bring it closer to reality?

[centerfire]

OK, this is getting interesting...A pressure trace like Recreational Software Incorporated sells?

Is the pressure trace indicating higher or lower by 25% than QL?

What changes do you make to case volume to bring it closer to reality?

The Pressure Trace told me what I already knew and what I've already posted. My posts have been fairly explicit and you're welcome to go back and reread them.

[Klem]

The Pressure Trace told me what I already knew and what I've already posted. My posts have been fairly explicit and you're welcome to go back and reread them.

[centerfire]

Velocity and pressure have an inverse correlation when using Weighting Factor whereas velocity and pressure have a (mostly) direct correlation using case capacity as a variable. QL over estimates velocity and pressure for the Grendel cartridge, if I use weighting factor to reduce velocity the software increases pressure. 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. You still have to be mindful of the case' artificial capacity because obviously the fill % is then incorrect. Again, it's not perfect.

The strain gauge only works attached directly to the barrel; the chamber specifically.

[centerfire]

That was my experience too. The pressures for some powders were way off, but one or two weren't bad.

I did, however, discover that the correction factors for velocity and pressure were the same percentage over the entire range of powder weights one would consider.

A Western Powders ballistician explained that the case is short enough that the primer discharge hits the base of the bullet and gets it moving before the charge lights off. That means that the bullet is moving when the powder starts merrily burning. The result is the case volume is changed and the initial velocity is not zero.

While repeatable as demonstrated by the fine accuracy, it is not predicable with the physics models used in QuickLoad.

I have not had an opportunity to see if we get similar results in other short cases like the BR series and the WSSM series.

That is an interesting theory and sounds plausible. The other cartridges I have chrono'd are higher volume than Grendel and do not have the large discrepancy.

[Klem]

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.