“MP 40” needs identification before any fit discussion. The historic MP 40 is a World War II-era German submachine gun. It is not the modern Smith & Wesson M&P40 pistol, and they share neither dimensions nor a carry context. In a current holster query, M&P40 normally means Smith & Wesson’s polymer-frame, striker-fired .40 S&W pistol. That still is not one physical pattern: the company has made full-size and Compact versions, original and M2.0 generations, several barrel lengths, and versions with or without a thumb safety.
Identify the exact variant
Read the slide marking and establish the generation, size, barrel length, and whether a thumb-safety lever is present. Full-size, Compact, and longer-slide pistols have different slide and grip envelopes. The external safety levers on a safety-equipped version need clear access; a shell that presses against, blocks, or cannot fully seat around a lever is not a safe fit. A mounted light, laser, altered sight, threaded barrel, compensator, or extended magazine can also change compatibility. A generic M&P label is not enough: Shield and other M&P-family pistols are separate models.
Compare the stated model designation with the unloaded pistol itself. Look at the trigger guard, ejection-port area, slide, sights, and controls rather than relying on a photograph or caliber alone. The correct test is functional: the firearm should seat without force, remain stable through ordinary movement, draw cleanly, and return without interference. If it rocks, binds, leaves a control obstructed, or must be pushed into place, stop and resolve the mismatch with the manufacturer or a qualified instructor.
Retention and trigger protection
Retention means the firearm remains seated through normal activity while a trained lawful user can make a deliberate, predictable draw. Passive retention comes from the molded shape and pressure of the shell. Active retention adds a separate deliberate release. Neither compensates for incorrect model fit. An adjustment should not deform the shell, squeeze a control, or create an erratic draw. Test retention only with an unloaded firearm in a controlled setting.
Complete trigger-guard coverage is essential. The material must remain firm enough that clothing, a drawstring, keys, or a collapsing edge cannot enter the trigger area. A rigid thermoplastic shell commonly keeps its opening shape; leather can be durable but requires inspection for softening, curling, damaged stitching, and collapse. Material type alone does not prove safety. Retire a setup that cracks, loses attachment hardware, flexes into the trigger area, or no longer retains the unloaded pistol consistently.
Position and reholstering
Inside-the-waistband, outside-the-waistband, appendix, hip, shoulder, ankle, and off-body positions place the same firearm in different relationships to the body and other people. Clothing, mobility, body shape, belt support, and local law matter. Assess normal sitting, driving, bending, reaching, and restroom use with an unloaded firearm. The position must permit muzzle control, a full secure grip, and a safe return without sweeping the support hand or trapping fabric in the opening.
Clips, loops, screws, and belts are safety components. Inspect them for looseness, cracks, bent hardware, and worn stitching. A shirt tail, drawstring, jacket lining, or belt edge can enter the opening when reholstering. Clear garments completely and, where safe, visually inspect the opening. Reholstering is never a speed exercise: do not force the pistol past resistance. If the opening has collapsed or cannot be safely accessed, remove the unloaded holster from the body before addressing the problem.
Handling, storage, and law
Follow the manual for the exact M&P40 and the core safety rules: keep the muzzle in a safe direction, treat the firearm as loaded until personally verified otherwise, keep the finger off the trigger until a lawful shot is intended, and know the target and what is beyond it. A thumb safety, where present, is not a substitute for those rules. Seek qualified instruction for loading, unloading, drawing, movement, and reholstering. Begin practice with the firearm unloaded and cleared in an area without live ammunition; follow range rules for live fire.
A holster is not a storage device. When the firearm is not under the direct control of an authorized user, secure it against unauthorized access and follow the maker’s instructions for locking devices. Carry licensing, prohibited locations, vehicle transport, property rules, notification duties, and storage rules differ by jurisdiction and change. Confirm the current law for each state, locality, destination, and property involved; obtain qualified local legal advice if a rule is unclear. Exact identification, full trigger coverage, sound retention, and careful handling matter far more than a broad model label.