Also, did you clean the gun before you went to the range?
Cliff
Right after the Shield was first introduced, John Connor wrote a review for either the American Handgunner or Guns Magazine. He reported that he cleaned and lubricated the pistol per instructions in the manual that came in the box. He then experienced few, if any problems in the initial break-in, and the gun worked. I broke in two Shields last year, both 9mm no safeties. I cleaned and lubed both. The first I shot about 200 rounds, a mix of 124 grain +P FMJ, and 147 grain Ranger/G2. The second was shot first with G2. Neither Shield jammed on me. No feeding problems.
Glocks gained a reputation of being increadibly reliable and myths circulated that they didn't even need to be lubed. Manufacturing quality and the design of other full-size, polymer frame pistols improved, and shooters began to discover that that these pistols functioned flawlessly out of the box, leading some to believe that the recommended 300-500 round break-in was no longer relevant. A couple of issues have arisen since then. First, manufacturers have designed super compact pistols in 380 and 9mm that are not simply chopped- down versions of full-size handguns. They have springs with greater tension, and tolerances my be tighter, or at least different. Secondly, the political hysteria coupled with mass shooting tragedies, as well as more interest in concealed carry, have caused a sharp i rise in demand for guns. Quality control seems to have been sidelined periodically. To counter the first, read the instruction manual before shooting, use a good, quality lube, generously, if necessary, and plan on at least 300 rounds to break in and ensure reliability. For the second issue, exercise the factory warranty.
Make sure your Shield is clean and lubricated, and head back to the range. Start with FMJ. If the problem continues, mark the magazine. If it jams with all mags, email S&W CS and in detail, describe your problem(s). When they send you and RMA shipping label, exercise your factory warranty. BTW, a guy I work with failed to lube a Glock 43 before shooting it for the first time. He got about 20 rounds down range before it seized up. Many years ago, I got exactly 101 rounds of FMJ thru a brand new G19 before the slide got sluggish. I'd believed stories that the copper colored stuff inside a new Glock was a lube Glock applied at the factory. That was the last new gun I ever tried to shoot without oil.