I have worked on this in the past and thought I had it resolved but I tried to shoot a S&W M&P 40 cal today and had feeding issues. As I remember the original problem was short loaded rounds would jam against the ranp going up to the chanber. Today also some rounds loaded long would not feed in the chamber. I have bought some Nosler 40 cal rounds that seem to work and were loaded at 1.11 COL. My reloads were at 1.17 ( to long) and some were 1.11 (to short) book is at 1.12 COL. Boy it was a while ago I had all these problems and I just don't remember if I solved it or not. Craig
Well I just remembered it needs to be loaded long as the short load always hung up on the feed ramp. The long loads today were hanging up in the mag causing all the today issues. I shortened all those rounds but then I had the the too short ramp issue. I think if load around 1.12 to 1.14ish COL I should be alright. I will try some rounds at these lengths. Craig
That's odd... I actually tried to get my 5" M&P .40 to feed jam with various loads, short, long, weak and could not. The worst I got was ejection problems with wimp loads.
Assuming you haven't added a +2,3,4 or 5 mag base without a correct spring for it, here's a couple of thoughts. Is it possible that your loads are on the low end and not cycling the slide totally rearward? This would cause a slow delayed feed and jam. Another thing, is a weak grip causing the same issue.
Hey Gary thanks for the suggestions. I will try all of that but I have worked on this problem like a year ago and forgot. A friend polished the feed ramp but that didn't seem to help. Going longer worked but I have always felt there is something else amis here. I am thinking something like the mag follower isn't pushing the bullet up high enough to chamber. I think I tried other mags but to no avail. Well this all is just something to do. Craig :-\
Well I made the length 1.14 on the remaining blue 200g and it was better but like 6 out of the 24 I had fixed chambered but hung up before full battery. On a better note I re-taper crimped the 9mm blue bullets that were a problem and all shot fine. I am scratching my head on the 40 cal. Craig