I'm guessing you've got a rough feedramp, either dirty or just bumpy. Something's catching the nose of the round...just a guess, tho. Mr. A! Help! Drivin' me crazy wondering... :?
Well, all we know right now is that your M40 MIGHT not like Federal Hydra-Shoks. I say try at least two other brands of JHPs before worrying. Want to do this on the cheap? Well, just head to your local Wally World and pick up two different boxes of cheap JHPs they stock: Winchester White Box Personal Protection/ Defense ammo and UMC-Remington JHPs. I have tried the UMCs in 9mm and though dirty, they fed well and were very accurate.Again and again, in the first 6 shots from a magazine there were 2 or 3 rounds that nosedived into the feedramp and stopped the slid. Once tapping the slide with knuckles was enough to make it close. After about 6 rounds, no problems. So what causes this kind of jam? I have old gun (maybe a weakish recoil spring?) and new magazines. Any thoughts on this?