I know there is a lot that I don’t know about firearms. So I sent off a few emails about over insertion.
The answer was unless you purposefully try to over insert the magazine, as in use more force than a human can generate, it won’t happen.
I’m not trying to change minds. I’m not even going to “cite my sources”. Just a recommendation, don’t believe everything you read on gun forums. Ask those that know for yourself.
I almost spent a lot of money on P07/P10-C mags when my full size mags will work just fine.
In the case of some pistols, like Glocks for example, everyone routinely runs longer mags and you never hear about over-insertion being a problem.
For a P-07 running a P-09 magazine, I have never heard about over-insertion being a problem. When I look at the design of the ejector in these guns, and how it is spring-loaded and rotating on the de-cocker or safety while also engaging the sear pin... I don't know if it is likely to be a problem. I guess if too much force was applied and it didn't deform the ejector itself, it might transfer that force to a pin and bend it? As I mentioned in an earlier post on this thread, I do pay attention to the wear pattern on this part when I happen to detail strip my frame for cleaning, inspection, etc. I have a spare ejector in case I ever need to replace one.
The P10 series and their ejectors are a whole different story. The ejector is a solid piece that is part of a frame insert. It has no movement, no room to give. There are numerous threads here showing photos of guns that have had their ejectors bent or broken. There are threads here where people are showing how the top-most round of a standard P10-C mag is making contact with an already deformed-looking ejector. People are manually bending or filing their ejectors to prevent this contact. So it's a common point of failure, even when you aren't over-inserting an extra length magazine. Seems like slamming home extra-length mags would just exacerbate the problem.