9mm OAL vs fps, note

[Nevada Ed]

While testing out some of my loads, I ran into a thing that
might be of interrest to some of you.

I tested the 115 and 124 gr plated bullets in one of my 9mm pistols
with a very short OAL of 1.10" and the 124gr at 1.09".

These were to see if a maximum fps would be improved over a 1.12" OAL?

I found out that this pistol did not like the 124gr at a OAL of just 1.09", and proved it by poor groups on my targets.

I used a full load of HS-6 and BE86, with the short 115gr plated bullet at 1.10"
and found out that this shorter length with these slower powders
produced loads that were only 96% of the 1.12" loads and lost 85fps or more.

The good news is, that with my short 3.5" barrel C9 pistol,
a 115gr fmj load with Bullseye or w231 and a OAL of 1.10"
gave me a load that was very close to the 4" factory data.

Happy Holidays to all.

 

[BLUEDOT37]

Those reductions in COAL" of .020-.030" aren't small differences but I don't readily see why they'd make accuracy/velocity worse unless the resultant pressure increase caused problems with the bullet's plating integrity?

If you had said the detrimental change was because you increased the the COAL" I could see that because some pistol barrels have little to no freebore/leade & a longer COAL" jams the bullet into the rifling causing potentially severe issues.

.

 

[stansdds]

Maybe the increase in free-bore jump impacted accuracy? Free-bore distance certainly impacts rifle accuracy.