Underpowered ammo velocities?

[T2C]

Velocity and port pressure are not directly related.
The powder burn rate can affect cycling greatly.

Thank you. A lot of people do not understand that.

[TomMcC]

Thank you. A lot of people do not understand that.

I still have a bit of English Radway Green SS109 they dumped on the surplus market some years ago. It only works in my carbine length rifle, but not my rifle length rifle. Burn rate was not optimize to run across the board on barrel lengths, but then they weren't making it for the American AR series.

[jsbhike]

I’m asking in reference to internal ballistics not terminal ballistics. I was just wondering after I observed a tuned gun fail to lock back a bolt while firing PMC bronze, and it made me wonder if that ammo is considered “underpowered” especially it’s posted velocity on the box is like 2900 FPS.

There isn't necessarily a relationship between projectile velocity and details on gas pressure going in to the system due to differences in the burning characteristics of the powders being used.

[T2C]

I still have a bit of English Radway Green SS109 they dumped on the surplus market some years ago. It only works in my carbine length rifle, but not my rifle length rifle. Burn rate was not optimize to run across the board on barrel lengths, but then they weren't making it for the American AR series.

We used Radway Green for shooting High Power Rifle matches when shooting at reduced distances. It shot well enough through my RRA match rifle to score plenty of X's on a MR-31 at 100 yards.

[Clint]

Yes, PMC Bronze is a known "low power" ammo in regards to cycling.

We use it for testing as the low limit for brass cased ammo.

I’m asking in reference to internal ballistics not terminal ballistics. I was just wondering after I observed a tuned gun fail to lock back a bolt while firing PMC bronze, and it made me wonder if that ammo is considered “underpowered” especially it’s posted velocity on the box is like 2900 FPS.

[Straight Shooter]

About anything from Hornady.
As for .223...Fiocchi..Guerilla...and a few more are slow even for .223.

[TomMcC]

We used Radway Green for shooting High Power Rifle matches when shooting at reduced distances. It shot well enough through my RRA match rifle to score plenty of X's on a MR-31 at 100 yards.

Weird, I wonder if they're different vintages. Yours worked in a 20 and mine works in a 14.5.