Shortening OAL = Higher Pressure = Cleaner Burning?

[anto]

I've been reading that generally the closer a load is to max, the cleaner burning it is. I've been working up some loads with 9mm 147gr Hardcast rounds, and noticed that 3.5gr Solo 1000 is indeed cleaner than 3.2gr at the same OAL.
Here's where my question about OAL comes into play.
I loaded 3.2gr Solo1k @ 1.147OAL and it was very smoky. I tried the same load @ 1.13OAL and it seemed much cleaner & was starting to show very mild primer flattening, nothing abnormal. I then tried out 3.5gr Solo1k @ 1.145OAL - there was less flattening & the load shot more accurately. If I slowly worked my way down to say, 1.14 or 1.135" OAL, wouldn't this increase the pressure and in turn, be cleaner burning?

[swerv512]

"cleaner burning" is referring to the amount of propellant burned. i think this is more a function of powder burn rate and barrel length. i'll do some QL later and see what happens...

[at_liberty]

I've been reading that generally the closer a load is to max, the cleaner burning it is. I've been working up some loads with 9mm 147gr Hardcast rounds, and noticed that 3.5gr Solo 1000 is indeed cleaner than 3.2gr at the same OAL.
Here's where my question about OAL comes into play.
I loaded 3.2gr Solo1k @ 1.147OAL and it was very smoky. I tried the same load @ 1.13OAL and it seemed much cleaner & was starting to show very mild primer flattening, nothing abnormal. I then tried out 3.5gr Solo1k @ 1.145OAL - there was less flattening & the load shot more accurately. If I slowly worked my way down to say, 1.14 or 1.135" OAL, wouldn't this increase the pressure and in turn, be cleaner burning?

1.135 is a very common OAL, and mags work well with it. Try it. Quite a bit shorter than that is possible too.

[HighLander51]

Decreasing overall length for any given powder will increase the pressure, and it will increase at a greater rate for heavier bullets in the same caliber. You have no way to measure pressure, only muzzle velocity, which does not indicate pressure. I have been shooting competition since the late 60's and load everything to near maximum. For the 9mm, I run 1.165".