I can't say that I use small rifle for 40 cal because I don't own one. BUT, I DO use small rifle primers in other cartridges like 9mm, 38spl, and 357 mag.
I don't shoot much 40 but I've loaded thousands of small rifle primers in 9mm and 38's, never had a problem with them, but only used them in revolvers. They all went bang.
Small rifle primers are called for in many .38 Super loads. They're usable, but you have to reduce the load and work back up. They have a thicker cup, so chances of a fail to fire increase.
I have used small rifle primers in 9mm and 40 S@W Back off the powder a grain or so as with any new component. Before loading prime a few cases and see if they go bang . Some brand primers are harder! for example the CCI military primers hardly dent in my pistols but Winchester Small rifle primers work in all my semi autos. I don't feel there is a safety problem just a if they go bang problem.