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Maybe I'm confusing terminology, but what exactly are you referring to as the "locking block"? From what I can see of the movement of the slide, the stress applied to the fracture area is where the stainless steel chassis is molded into the poly frame, not back at the sear assembley. Slide moves forward untill barrel ramps up locking tight in the slide, slide makes upward movement untill limited by the lug on the chassis. Maybe I'm calling it the wrong term, or have to dig deeper to see where the movement stops at, I stopped looking when I found movement that matched the direction of fracture.


I am assuming that you are calling the locking block as 'stainless steel chassis'. May be this image will help you with correct jargon.Brownells' M&P diagram



I am not getting confused with the sear assy. I just mentioned that the locking block and sear assy are 2 major MIM parts AFAIK.
 

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I am assuming that you are calling the locking block as 'stainless steel chassis'. May be this image will help you with correct jargon.Brownells' M&P diagram



I am not getting confused with the sear assy. I just mentioned that the locking block and sear assy are 2 major MIM parts AFAIK.


OK, we're on the same page now. Yes I have been talking about the front locking block. For some reason I had it in my head that it was part of the chassis system as talked about in S&W's flash presentation.



http://www.smith-wesson.com/wcsstore/SmWes...sh/swpopup.html



But I see now that what I was referring to as one assy, is actually the front locking block, sear locking block, and then the stainless rails embedded in the frame.



As for the locking block being MIM parts, don't know, I'm not about to take a file to em in order to check. I would be really suprised if they were however as MIM parts are good in compression, but not so much in torsional stress such as the locking block would encounter.



Thanks for getting me straightened out on the correct terminology.
 

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OK, we're on the same page now. Yes I have been talking about the front locking block. For some reason I had it in my head that it was part of the chassis system as talked about in S&W's flash presentation.



http://www.smith-wesson.com/wcsstore/SmWes...sh/swpopup.html



But I see now that what I was referring to as one assy, is actually the front locking block, sear locking block, and then the stainless rails embedded in the frame.



As for the locking block being MIM parts, don't know, I'm not about to take a file to em in order to check. I would be really suprised if they were however as MIM parts are good in compression, but not so much in torsional stress such as the locking block would encounter.



Thanks for getting me straightened out on the correct terminology.
I'm fairly certain that they're MIM.
 

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As for the locking block being MIM parts, don't know, I'm not about to take a file to em in order to check. I would be really suprised if they were however as MIM parts are good in compression, but not so much in torsional stress such as the locking block would encounter.


I know I'm going to regret this, but just how do you see torsional stress in the locking block? Compression and shear, yes, torsion?????????? The block (part of it) engages the inclined plane on the bottom of the barrel and unlocks the barrel from the slide and acts as a stop. With the slide going into battery, the block engages another inclined plane and cams the barrel back into engagement with the slide.
 

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Discussion Starter #267
I've seen one broken M&P locking block, and it was here on mp-pistol.com. I forwarded the image to a contact at Smith I trust and he said it's extremely rare and simply a matter of a defective part. That could just as easily happen in a non-MIM locking block (see Beretta, Glock, SIG for examples ... though some of them may now be using MIM'd locking blocks, too).



Regardless of what the locking block is made from, it's clearly not a weak link in the chain.
 

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Discussion Starter #268
Tested the gun yesterday for accuracy. There was substantially greater variation in group size and point of impact than in previous tests, but the gun still averaged 2.88" 5-shot groups at 25yd.



The gun hasn't been cleaned in close to 9,500 rounds. Next week we'll be performing a very thorough cleaning, especially of the chamber and bore, and then repeating the test one last time.



Pics of some groups along with other information about yesterday's shoot are posted at pistol-training.com.
 

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Discussion Starter #269
This will be going up on pistol-training.com Monday, but thought I'd give you guys the news right away.



Yesterday I finally got around to doing the "thoroughly cleaned gun" test on the endurance gun. Remember, this is a gun with more than 62,000 rounds through it and with a cracked slide:







Five groups at 25yd fired from the bench averaged 1.83 inches. That's a third of an inch greater size than when the gun was brand new.
 

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Thanks Todd for the follow up, wondering when you would get around to the cleaning and another accuracy test. It appears a thorough cleaning improved accuracy from the test pistol considerably, even with a cracked slide. Actually, this last accuracy test (1.50”) using the HST round shows little loss from initial accuracy test of 1.46” in April of 2008.
 

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Is it Melonite treated barrel that is responsible for this accuracy even after 62K rounds apart from the slide to barrel lock up?
 

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Discussion Starter #273
Is it Melonite treated barrel that is responsible for this accuracy even after 62K rounds apart from the slide to barrel lock up?


It's primarily attributable to the the quality of the steel and the basic design of the gun which provides and maintains excellent slide/barrel lock-up. In my experience, running hot ammo in the 9mm M&Ps (such as the 124gr +p HST I've been using for the accuracy tests) turns in the best result because the gun stays locked up the most consistently.
 

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It's primarily attributable to the the quality of the steel and the basic design of the gun which provides and maintains excellent slide/barrel lock-up. In my experience, running hot ammo in the 9mm M&Ps (such as the 124gr +p HST I've been using for the accuracy tests) turns in the best result because the gun stays locked up the most consistently.




nice thread sir ToddG... keep it coming, it will be a great help for me as newbie in this site! tnx
 

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Discussion Starter #276
Thanks Todd for a great test and write up for everyone to learn from.


I hated every second of it, of course. But I did it for you guys!




Hopefully, we'll finally be announcing our next 50,000 round endurance test before the end of April. It's not going to be a S&W ...
 

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i say beretta.
That would be to assume Beretta has an interest in marketing handguns. I doubt it unless things have changed in the last few years.



I could see it if Todd got the green light (no pun intended) on the new Beretta.



God Bless,

David
 
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