Grendel gas pressures vs. 5.56 pressures....

[rasp65]

Variable The powder is burned in the first few inches of the bullets travel. When the high pressure/velocity gas comes in contact with the atmospheric oxygen then it reburns causing the enormous flash.

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Several years ago Quickload overestimated the pressure on some (not all) Grendel loadings. Some reloaders were terrified by high Quickload results, even on loadings that had been physically pressure tested by Bill Alexander as safe. Bill Alexander explained that the geometry of the Grendel cartridge somehow did not meet certain assumptions in the Quickload software. I do not know if the glitch in Quickload has been fixed.

This issue comes up every few years.

Yeah, I know Quickload is kind of verboten for Grendel. I've posted about it many times in the past as well. Without any other source of data to work with though, I gotta take whatever I can get.

It would please me greatly if the actual muzzle pressures for the Grendel were much lower. I just can't afford piezo electric gauges and other fancy sensor stuff to find out.

I need to pick a can for a Grendel lightweight build, and I need to know just how much "bang" needs caught in the can before I can make the best decision about what can to catch it in.LOL

Variable The powder is burned in the first few inches of the bullets travel. When the high pressure/velocity gas comes in contact with the atmospheric oxygen then it reburns causing the enormous flash.

I agree --sort of---. The powder is mostly consumed early on, but it doesn't combust completely. The longer the barrel, the more complete the combustion, and less flash (from atmospheric re-ignition) in my experience. Getting burn percentage numbers helps me guess how bad the flash will be, plus percentage of unconsumed powder is important to gauge how much unburnt powder will be acting as "sandblasting" media launched at high velocity into the baffles in a can. The first blast baffle takes the brunt of the errosion, but if there is a lot, it also affects the successive baffles as well.

In the videos that I posted links to with Titanium cans emitting sparks, unburnt powder is likely the primary culprit. The solid particles impact the Ti surfaces in the can and ablate off tiny specks of Ti. Those Ti specks are what are seen as brilliant white sparks traveling down range from the muzzle. Even inconel and stellite errode, but they resist it better and don't ignite like Ti does (creating additional visible signature).

[nincomp]

Yeah, I know Quickload is kind of verboten for Grendel. I've posted about it many times in the past as well.

I knew that you had brought up the Quickload issues before. I just figured that it would not hurt to bring it up again.

Has anyone gotten pressure curves for Hornady's own loadings. Hopefully they developed them as they developed the powder blend for those rounds. They may have it listed as port pressures for different configurations of AR15's.

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I knew that you had brought up the Quickload issues before. I just figured that it would not hurt to bring it up again. Very True Sir.

Has anyone gotten pressure curves for Hornady's own loadings. Hopefully they developed them as they developed the powder blend for those rounds. They may have it listed as port pressures for different configurations of AR15's.

I sent them the following message yesterday morning:

Hi,

I shoot your excellent 6.5 Grendel 123 Amax load (8150) through multiple rifles I have. My shortest barrel used is a registered short barreled rifle that is 10.5" in barrel length. I use a .30 caliber suppressor on it (AAC 762-SD), and it works very well. That being said, it's a very large suppressor, and is really overkill for that application.

I want to build a new 12.5" barreled Grendel, and use a smaller, lighter .30 caliber suppressor on it. I can make a much better choice in my selection if I can find out what the muzzle pressure ("uncorking") is in psi for an average 12.5" Grendel barrel using your 123gr. Amax load (8150).

By comparison: I also have an 11.5" 5.56 rifle (Colt 6933) that has an approximate muzzle pressure of 10,140psi using M855 ball ammunition. It can be suppressed reasonably well with a smaller suppressor. I know there is more to it than that, but to keep it short, it would be a big help to me in selecting a reasonable suppressor size if I knew about how much muzzle pressure I could expect from your 123 Amax load (8150).

So my questions are:

1.) What is the approximate pressure at the muzzle of a 12.5" Grendel barrel firing your 123gr. Amax load?

2.) Approximately what percentage of the powder will be consumed in 12.5" of barrel?

Thanks in advance for any help you may be able to provide!

Respectfully,
XXXXX XXXXXXX

Haven't heard back from them yet, but hopefully I will. I'll post up anything I get.

I have a hunch the Quickload presssures really are too high. I sure hope so. If they really are as high at 12.5" as the quickload curve would seem to indicate, then I think I'm totally screwed on using a lightweight can. It would likely be short lived in that scenario. It will also significantly sour my whole goal for a lightweight build. That many bucks budgeted for the build--- needs to yield something significant to justify it.