Originally Posted by AustinTx
The Glock pistol, since it has a plastic frame, has all sorts of waves traveling through it, when it fires. IOW, it sort of behaves like Jello. Anything, rigid, attached to the rails will change the frames motion. Arc Angel calls it harmonic monition, I think. If that's wrong, he will correct this. That's a good enough name for it, IMO. Actually, some steel rifle barrels will look like a sine wave, with high speed photography. That's why proper rifle bedding improves accuracy, sometime.
I couldn't find the slow motion video of Glock frame flex that Austin mentions but what he describes is exactly what is happening during firing.
I was able to find this short clip of it,you may have to watch it a couple of times but it is their none the less.
You can see the dust cover flexing and that flex is transmitted through the entire frame. SJ 40