Leather too Light
I find many Holster makers use leather that is too light for the Job! The Gun is too loose in the holsters after some use. That is why I use 8-9 oz Shoulder with a 2-3 oz lining, it makes the leather a lot harder to work, but makes a holster that holds the gun better in the long run.
Leather is such a variable.
I guess because not much gets more "natural" than vegetable tanned leather.
Some leather from some tanneries seems to be much more dense and compacted and so a thinner leather can be used.
I know that Lou Alessi uses leather that is quite thin but, it holds it's shape really well.
Muir & McDonald & Hermann Oak both have great leather.
I especially like Muir & McDonald for floral tooling on leather.
It carves beautifully & the stamping impressions stay so crisp.