Haenelistklasse Posted February 20, 2020 Report Share Posted February 20, 2020 Hello, I was just wondering if anyone has experience with MP40 lower interchangeability. I have an ayf 43 receiver but am looking at a cool lower that is a bnz 41. Does anyone know if this match would work? or am I just better off sticking to an ayf lower? The lower is in another state so can not try out. Link to comment Share on other sites More sharing options...
DARIVS Posted February 20, 2020 Report Share Posted February 20, 2020 I believe MP-40 parts were stamped to tight tolerances, but the parts were assembled and fitted and riveted by hand, so there could be fitment issues in mismatched parts that involve rivets, such as the placement of the magwell on the receiver tube. In that case, a different rivet hole location would affect feeding into the chamber. Magwell placement affecting reliability is the biggest issue I have seen with the few mismatched MP-40's I have seen. However, fitting a mismatched lower to the upper receiver doesn't rely on rivet location, so you should be okay. At worst, the take down button in the bottom that locks the receiver when it's rotated into position may have some slop because the side of the hole it engages in may be worn, allowing the receiver tube to be able to rotate a small amount within the lower. Careful peening the edge of the hole with a light hammer can narrow the width of the hole and narrow the gap for the take down pit so the receiver doesn't move, if you find the slop is extreme. A mixed upper/lower should work just fine. It really depends on the individual parts. It certainly won't hurt to try swapping the parts out and taking it out for a test run. Link to comment Share on other sites More sharing options...
TSMGguy Posted February 20, 2020 Report Share Posted February 20, 2020 Right. The Germans never attained true interchangability as defined by the US Army Ordnance Department in the US. Each MP-40 was built up by a single trained assembler, who could and did make minor adjustments during the build. The US standard was different: Every part had to fit every weapon, with no fitting allowed. A Colt M1911 slide from 1918 has to fit a 1944 Remington Rand M1911A1 frame. It does. Every time. This was seen as a bit of a production miracle at the time, and it was. I ramble. That lower will fit, or it won't. It'll be close either way, but it may fit fine. It's just that fit isn't assured because it wasn't designed in. Because original fit wasn't assured before fitting, I'd take that as license to do a little fitting of your own. Link to comment Share on other sites More sharing options...
michaelkih Posted February 24, 2020 Report Share Posted February 24, 2020 All I will say is that my MP40 pre sample is 8 different MP40s. LOL. Runs perfect. Link to comment Share on other sites More sharing options...
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