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It appears that there is a downward frame bow to my M&P9, just forward of the trigger guard. I e-mailed S&W and they said that there is a bow and that I don't need to do anything about it. I replied that I'd like an explaination but I haven't heard back form them yet. Does anyone have any ideas about this? I have a Sigma (1st Gen) and the frame does not bow. Yes, I know they're not the same but they appear to be closely related.......
 

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The all have them, and they do not effect performance, at least nobodu has been able to tie any failures of any kind to them.



While I have not, nor will I ever mind you, taken an MP frame and cross sectioned it, the bow is a side effect of molding in the rail on the bottom of the dust cover. Just by looking at molded component ther appears to be thick spot in the material at the transition from the trigger guard and rail section. When the mold is filled and allowed to cool, the mass of material at this thick spot cools and shrinks differently from the rest of the part. In the case of the MP frame that differemce appears as the "bent" dust cover. The "bending" can be controlled by either modifying the part design and tool, changing the molding processes... All these add cost to the past either up front, or to each individual part as it comes off the tool due to increased cycle times and such. Given that the bow has no effect on performacne, but is simply an aesthetic thing, I guess SW chose to not mess with it.
 

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Sure, pick on my M&P :wink:



Actually until you pointed it out with that very pic, I had never been able to notice what everyone was talking about. I never notice it when handling the gun in person.



Weird. I think its just the lighting in those pics make it more pronounced.
 

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It may be a manufacturing thing, but I still ask why can't the S&W engineers determine a way to may it straight like most of the other plastic pistols???



This is the reason a bought a compact, it isn't as noticeable.





 

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itr674 said:
It may be a manufacturing thing, but I still ask why can't the S&W engineers determine a way to may it straight like most of the other plastic pistols???


Most likely, it is a cost issue and nothing more. To fix the issue one would have to redesign the frame, redesign/recut the tool or both. Considering the cost of injection molding tools, especially those meant for higher volumes with multiple cavities, the cost could easily add hundred of thousands of dollars to the capital expenditures. These additional thousands of dollars would have to be ammortozed over the parts coming off the tool. This could have increased the cost to above the targets. The other possible solution is to change to molding parameters. Usually these result in leaving the part in the tool longer and therefore means less parts off the tool per day. The end result is again higher costs. Then there is also the possibility that they dont know how to fix it.



From a business standpoint it makes sense to leave well enough alone. Having faced this dilemma I can understand the choice. And that is coming from the engineer.
 

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It is a design feature and and and a very good one.They may have patten on it.It is pretty obvious if you examen the pistol closely.Keep looking.



Ed
 

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If you're looking at the pistol completely assembled, it may not be entirely molding. Some 1911's suffer the same issue due to tolerances between frame & slide rails and the upward pressure of the recoil spring. I've measured a couple of frames with straight edges and -at least on the ones I actually measured-the warpage was minimal.
 
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