Bought internet brass, help....

[engineermike]

Case length has nothing to do with COL unless you over crimp and then it plays hell with accuracy. I however do trim a lot of pistol brass because I crimp everything. But I don't think that 9mm brass is considered straight wall brass either. If you are loading magnum loads in a revolver then case length might be a little more important as you are usually using a roll crimp and that is a whole different animal. Ever since I started using a standard length to my pistol brass I have a lot less fliers on my targets but that's just my results. I have yet to blow a pistol apart by over crimping with a taper crimp but my bullet patterns are a lot better when I don't.

 

[Mobuck]

Since the 9x19 heaspaces off the case mouth, it IS possible for a case to be too short but since the case is also tapered, this is usually not a noticeable problem(I've actually seen a 9x19 feed and fire a 380ACP). Cases can also be too long and prevent complete lockup.
In the many thousands of 9x19 that I've loaded, I've NEVER trimmed a case and likewise NEVER had a case length related malfunction. It could happen tomorrow but, it hasn't happened yet.

 

[1SOW]

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Lyman's also states not to seat bullet too deeply due to creation of excessive pressures. So wouldn't seating a bullet to normal depth in a case that is shorter than the called out spec length cause increased pressures?

Your press doesn't seat to A seating depth. It seats to AN OAL. With shorter cases you'll just have shorter/less brass holding the bullet (slightly less neck tension).
The interior case volume will be the same regardless of case length in 9mm.

Load 'em up and shoot 'em.