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Thread: M&P9 barrel saga

  1. #1
    Site Supporter DocGKR's Avatar
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    M&P9 barrel saga

    I recently picked up a new M&P9 (Ser # HAHxxxx), as it was of post July 2012 production, I assumed it had a new barrel. Mark Housel put an RMR02 on it and I added the normal stippling, Apex Duty Kit, and Catalyst mag release:


    Then I went to shoot it with Fed AE9FP 147 gr FMJ. Even when shot from the bench off sandbags, I still got 2-3 flyers in every 10 shot group at 25 yds:


    Thinking I might not know how to shoot anymore, I grabbed the G19 w/RMR02 and OEM barrel I carried all last year and shot a 10 rd group at 25 yds. I quickly realized there was a problem with the M&P9, not me, as the G19 shot fine:


    Grabbed a known good older 1/18 twist M&P9 upper assembly I had and dropped it on the new lower--shot a bit better:


    Next, tried putting a KKM drop-in barrel I had lying around in the new M&P9:


    Shot pretty good, so this is what I used at the recent Ken Hackathorn class: http://pistol-forum.com/showthread.p...stro-Valley-CA

    Now I was still curious why the M&P9 shot so badly with the OEM barrel. After looking at it, I noticed there was no dimple on the underside of the barrel--thus indicating an older 1/18 twist barrel, as shown by Hilton Yam at MSW: http://modernserviceweapons.com/?p=3719 Careful inspection of twist rate indicated it was an old 1/18 twist barrel.

    S&W was kind enough to send me a new 1/10 twist M&P9 barrel w/dimple to replace the older 1/18 barrel that some how inadvertently had been put in my pistol as it was being built.

    When I tried the new 1/10 twist OEM replacement barrel in my new M&P9, the results were not ideal despite trying several groups:




    Finally I dropped the KKM barrel back in and got a reasonable group:


    Bizzarre...
    Last edited by DocGKR; 07-02-2013 at 01:19 AM.

  2. #2
    Member orionz06's Avatar
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    Interesting. I am gonna guess that S&W will not be swapping barrels for the poor saps who own M&P's with the older barrels.
    Think for yourself. Question authority.

  3. #3
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    Thanks for the great post. I'm surprised the new barrel did not help much. I think there was another person here who was having issues with the M&P accuracy and a new barrel fixed it.

    It is the hit or miss on this issue that keeps me out of the M&P line. Even though my M&P shoots ok, I'm not tempting fate.

  4. #4
    New Member BLR's Avatar
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    Wow.

    Food for thought on striker fired gun designs:

    Cocking the hammer on the Browning tilt barrel principal has more influence on slide velocity than recoil spring weight (within normal windows). Including delaying unlocking of the barrel. That is why flat bottom/small radius FPSs are so popular with the 1911/P35 crowd.

  5. #5
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    Been waiting a very long time to buy a M&P 9mm or even a Gen 4 G19.

    I'm just waiting for the Doc to say GTG

    Until then I will use my late 90`s`s metal frame DA Pistols

  6. #6
    We are diminished
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    I've said all along, switching to 1/10 twist is not going to fix this problem.

    Ernest Langdon developed a solution to the accuracy problem back in '07 -- that's six years ago -- with the engineers at Smith. It used the same twist as the original barrel... which is the same twist Smith has used in all its 9mm guns going back to the beginning of time. I have one of those barrels. It was first shot extensively by Ernest and then got wrung out quite a bit by Gordon Carrell before dropping in my lap. It shoots ridiculously tight groups with any ammo I've tried.

    The problem, as Bill pointed out, is the barrel dwell time.

    I'm sure there is some legitimate corporate/engineering reason why Smith doesn't just adopt the Langdon barrel profile. But for the life of me I can't imagine what it is or how it could possibly be more costly than the continuous beating the M&P's reputation gets.

  7. #7
    New Member BLR's Avatar
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    Quote Originally Posted by ToddG View Post
    I've said all along, switching to 1/10 twist is not going to fix this problem.

    Ernest Langdon developed a solution to the accuracy problem back in '07 -- that's six years ago -- with the engineers at Smith. It used the same twist as the original barrel... which is the same twist Smith has used in all its 9mm guns going back to the beginning of time. I have one of those barrels. It was first shot extensively by Ernest and then got wrung out quite a bit by Gordon Carrell before dropping in my lap. It shoots ridiculously tight groups with any ammo I've tried.

    The problem, as Bill pointed out, is the barrel dwell time.

    I'm sure there is some legitimate corporate/engineering reason why Smith doesn't just adopt the Langdon barrel profile. But for the life of me I can't imagine what it is or how it could possibly be more costly than the continuous beating the M&P's reputation gets.
    I'd venture to say it's because 99.99% of the M&P crowd doesn't care if it shoots patterns rather than groups. That said, I'd /personally/ take a M&P over any other striker fired pistol.

    I'm still of the opinion that a poly framed P35 sans mag safety would be a huge step forward in pistol designs. But that's just me talking out of my rear end

    PS - have it use 92 or 226 mags.

  8. #8
    Site Supporter JodyH's Avatar
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    Quote Originally Posted by Bill Riehl View Post
    I'd venture to say it's because 99.99% of the M&P crowd doesn't care if it shoots patterns rather than groups.
    I'd venture to say it's because 99.99% of the M&P crowd doesn't know if it shoots patterns rather than groups.

    fixed it for you
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  9. #9
    New Member BLR's Avatar
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    Quote Originally Posted by JodyH View Post
    I'd venture to say it's because 99.99% of the M&P crowd doesn't know if it shoots patterns rather than groups.

    fixed it for you
    I stand corrected

    Seriously, why tolerate that from a pistol...with a RD sight....off bags? I'd be three kinds of pissy if I had a pistol that did that at 25yrds.

    Anyone have a picture of the Langdon bbl? Just curious about it right now.

  10. #10
    Could the hammer cocking by slide effect on barrel dwell time be one of the reasons HK45 and HK P30 shoot so well?
    Is it harder to get a striker fired pistol to shoot as well ?
    It would seem that the longer the barrel remains locked up, or at least in a parallel relationship to the slide and thus sights, the more accurate the pistol is likely to be. Old bullseye shooters in the 1970s used to tell me this.
    I think that, the sooner the barrel is allowed to tilt and unlock, the more ammo variation would impact accuracy because barrel might be tilting before the bullet departed. Ammo pressure variations could thus cause bullet departure at various barrel tilts. If the barrel stays locked up and /or parallel longer ammo variation should affect it less.

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