Today I shot some fresh 40 S&W loads using Hodgdon Longshot.
Two loads: 7.3grains and 7.5 grains behind 165 grain HP Montana gold.
The groups were decent and felt lively compared to my Unique powder loads.

But a few times while shooting the 7.5 grain longshot rounds my slide stayed open without chambering the next round and “once” it did not completely feed a round into the chamber fully but I had to push the slide up to lock it in. I shot new starline brass and OAL of 1.125

Also the hodgdon site states the min and max loads for 165gr 40's are 7.3 to 7.8 "small Window"
After running out of longshot rounds I oiled the slide and ran my unique loads with out any trouble.
Is Longshot too much at high velosity for the 40?
Any comments, Thanks Guys.
Vin

Hard to sat crony it the only way to find what the velocity is.

Sounds like your slide lock is moving during recoil. What pistol? Also, look to see if your bullets are hitting the slide lock. The follower generally lifts the lock but I' be seen bullets catch the lock.