6.5 Grendel barrel Length?????

[kmon]

Thanks for the reply. I've been casually researching this some tonight, and there is indeed an interesting phenomenae, where once the pressure falls, the burn rate falls precipitously as well. Which makes sense, since high density (i.e. high pressure) and hot (i.e. high pressure; PV=nRT) gas will transfer heat more agressively into the powder to cause it to burn faster. And vice versa, and if the pressure gets low enough, it essentially quenches the burn. Fascinating science.

Here, I'm just tagging these here for future read, which perhaps dive into the topic more:

https://apps.dtic.mil/dtic/tr/fulltext/u2/462060.pdf

https://apps.dtic.mil/dtic/tr/fulltext/u2/676246.pdf

I tried to explain in a short form what myself and some other engineers had a discussion about a few years ago on internal ballistics powder burn and pressure in an earlier post in this thread. Powder burns most efficiently under heat and pressure, a simple example of this pour out a measure of powder that you are using in your Grendel onto dry concrete or steel and light it with a match. Watch how long it takes t to burn in the open air. Then think about how fast it burns when in an enclosed environment such as the brass in the chamber of a rifle.

this video is not bad on going over powder burn in the chamber

https://www.youtube.com/watch?v=AqMzUsTTFnA

Ever notice how on light weight barrels very shortly after the chamber they start getting smaller in diameter, that is safely possible because the pressures in that location have dropped to the point less material is required to contain the internal pressure.

LR interesting example with the powder burns on the hands. In the case of the revolver heavy roll crimps are used to hold the bullet in place longer for better ignition and burn of the powder before the bullet starts to move and the bullet in most cases is still being engraved by the rifling when the base of the bullet is at the barrel cylinder gap under high pressure. The larger the barrel cylinder gap the more gas and flames escape there. Ever not get a good crimp on a revolver reload? If you have that you will have more unburnt powder show up or at least more partially burnt powder.