Alright, I just ran some numbers using GRT.Currently doing load development with N105 and 190 gr Sub-X. COL 2.09. 6.5" barrel with V7 proprietary gas tube (shorter than pistol gas).


8 gr of N105 got the bolt 2/3rds of the way back. Muzzle psi was 6880. If I seat out at 2.24 at 8 gr, muzzle psi will be 7280 and velocity will be around 1000 fps.


Ran data with my N110 loads seated at same COL and the lowest charge I tried was 8 gr at just below 900 fps with a muzzle psi of 5800. Those cycled and held the bolt open.


Does this have to do with the different powder pressure curves? And how does this play out with how quiet a load is? Less muzzle psi should mean more quiet. I'm assuming the difference is in the percentage of powder actually burned?
Any thoughts?

My GUESS is the N105 has a pressure peak that drops way faster than N110, even though muzzle pressure may be higher with N105.  At the gas port the N110 being slower, probably has a higher pressure than the N105.

Without a strain guage's down the barrel you will never know.

That’s the only thing that makes sense to me.

This was my line of thinking as well. That's pretty damn interesting though.

The pressure curve is related to burn rate, and thus burn time.  If a particular mass of powder burns completely well before the bullet reaches the muzzle, you’ll have a lower muzzle pressure.  On the other hand, if it burns completely just before the bullet exits the muzzle, you’ll have higher muzzle pressure.  And of course if it doesn’t completely burn until after the bullet exits, you’ll have a completely different effect.

MV is related to the pressure curve, but also a whole lot of other factors, so it’s really only mentally useful to think about when comparing different loads of the same powder.

GRT should tell you not only whether or not the powder is burned 100%, but (on one of the curves) where in the process burnout occurs.  When tweaking a load for a particular velocity range, that information might help you zero in on your load.