I've discovered a bullet set-back problem with my M&P

I've discovered a bullet set-back problem with my M&P

This is a discussion on I've discovered a bullet set-back problem with my M&P within the General Firearm Discussion forums, part of the Related Topics category; I was unloading a mag and noticed two rounds were set back - significantly. Needless to say this was troubling. So, I load up a ...

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Thread: I've discovered a bullet set-back problem with my M&P

  1. #1
    Senior Moderator
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    I've discovered a bullet set-back problem with my M&P

    I was unloading a mag and noticed two rounds were set back - significantly. Needless to say this was troubling.

    So, I load up a mag and rack the slide and slowly release it to see if that'll help me see what's going on. The nose of the HS JHP contacts the feed ramp and stops! I remove my hand from the slide and the bullet holds the slide open! Well, so what I think, it probably behaves differently at full speed, but then something caused two bullets to set back.

    So I do the same thing with a Beretta 92FS, an H&P USP, and a Glock and the round slides right in the chamber. So why does my M&P not do this?

    So, I do another test - two in fact.

    I measured two Hydra Shok rounds, one at 1.103" and one 1.100" long. I used one round for a pull and drop, release and the other for a slide lock release test. I used a dial caliper to measure the length of the round after each chambering.

    Here's the results. The first method is pulling the slide to the rear and dropping it cleanly. The second method was releasing the slide freely via the slide lock lever, common in 'gaming'.

    1.103"........1.100"
    method 1....method 2
    1 1.102......1.095
    2 1.101......1.090
    3 1.100......1.085
    4 1.097......1.081
    5 1.097......1.077
    6 1.096......1.076
    7 1.094......1.073
    8 1.093......1.071
    9 1.092......1.070
    10 1.092.....1.068
    11 1.091.....1.066
    12 1.091.....1.064
    13 1.091.....1.063
    14 1.091.....1.061
    15 1.091.....1.061
    16 1.091.....1.060
    17 1.0905....1.057
    18 1.0905....1.056
    19 1.090......1.052
    20 1.090......1.050

    Pulling the slide to the rear and releasing it 20 times produced a set back of 0.013"

    Releasing the slide via the slide lock 20 times produced a set back of 0.050"

    I am eagerly anticipating doing these same two tests with a Sig 226, H&K USP, Glock 17, and a Beretta 92FS. Probably gonna be this weekend before I can run the tests.

    I thought it was especially interesting that dropping the slide from the slide stop produced a much larger back set than pulling the slide to the rear.

    So what's the point? The point is I had to mysterious set backs in my M&P and I need to know why and how it happened. It almost seems that slower slide speeds cause more force on the round than higher slide speeds.
    I'm too young to be this old!
    Getting old isn't good for you!


  2. #2
    VIP Member Array Rob72's Avatar
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    Tangle, how does your chamber look? My first step would be a felt bob and some 800 grit lapping compound

  3. #3
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    Having checked my USP, I get no noticeable setback for 10 or more chambering of the same round. I am using Fed hyrashocks and Speer gold dots.
    try running your finger along the feed ramp. If it is rough it may need some polishing.
    A different type of bullet might work better, I know the HS initially hung up in my SA Champ , when it was new. now the feed ramp is broke in , no problems.
    Bullet setback (especially in .40 is a bad thing alright). Hope ya get it worked out o.k.
    "In matters of style, swim with the current; in matters of principle, stand like a rock." Thomas Jefferson


    Nemo Me Impune Lacesset

  4. #4
    Ex Member Array Pete's Avatar
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    My solution to this problem in my Sig P232 (with the join between the feed ramp and barrel) was to use Cor-Bon Pow'R Balls. They don't grip the feed ramp.

  5. #5
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    Huh, another problem with the M&P... who woulda thought?

    Has it caused any malfunctions yet?
    "Just blame Sixto"

  6. #6
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    The feed ramp is as smooth and uniform as it can be. Even after 1550 rounds, the finish on the feed ramp looks like it's never been fired.

    rocky,
    The USP is one sweet gun except for that disgusting DA trigger. It almost seems unfair to compare a gun to a USP.

    SIXTO,
    Other than what I consider a once in a life time fluke trigger disconnect problem, this M&P has not had one mal of any kind in 1550 rounds and that was without any cleaning. AH-HA! I cleaned it!

    This thing runs like a champ, but somewhere along the way something has happened that caused two rounds to set back, and they set back more than the worse case of the two tests above.

    The baffling thing is that a round will hang on that smooth feed ramp. I've talked to some other M&P owners and one stated that no matter how he operated the slide he could not get a round to hang on the feed ramp. Mine hangs with JHPs and ball ammo as well.

    Oops, I forgot:
    Rob,
    Good point, but it's not getting to the chamber; it hangs about midway down the short feed ramp. The round is at a slightly upward angle.

    And, .02,
    It's not catching on a joint, it's right on the ramp. I'm tellin' ya it looks impossible.
    I'm too young to be this old!
    Getting old isn't good for you!

  7. #7
    VIP Member Array Bud White's Avatar
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    I tell ya them 40's are dangerous

    got a pic of how its doing it ?

  8. #8
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    You know Bud that's not a bad idea, I'm gonna take a pic and post it.
    I'm too young to be this old!
    Getting old isn't good for you!

  9. #9
    VIP Member Array Bud White's Avatar
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    Wonder if its not sliding smoothly up the breach face and thats why you get the binding? Anyways lets see the pic

  10. #10
    VIP Member Array Janq's Avatar
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    Tangle,

    I saw your thread this morning and then just moments ago while at SigForum I came across the following thread with relevant information...

    '.40 Cal.'
    http://sigforum.com/eve/forums/a/tpc...35/m/551100088

    - Janq
    "Killers who are not deterred by laws against murder are not going to be deterred by laws against guns. " - Robert A. Levy

    "A license to carry a concealed weapon does not make you a free-lance policeman." - Florida Div. of Licensing

  11. #11
    VIP Member Array Redneck Repairs's Avatar
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    Setback is common with all non fixed barrel autos . It creates issues with high pressure loads like the .40 , .357 sig , ect. . You can limit setback somewhat by polishing the feed ramp to mirror finish , but will never eleminate it . Which is why you should " load once " and then put that round in your practice rounds while replenishing your mag from the fresh box . As you load and unload the rounds impacting the feed ramp will force the bullet progressivley back into the case, so the top 1 or two rounds of your " carry mag " will over time be a problem . Glock actualy tried to limit this issue in thier 40 cals , but in doing so set up the exact reason we see glock kabooms since it did help with setback some , but left more case unsupported.
    My best advise is polish ( not grind or change angles by any means ) the ramp , and then limit the number of times you chamber any one cartage .
    Make sure you get full value out of today , Do something worthwhile, because what you do today will cost you one day off the rest of your life .
    We only begin to understand folks after we stop and think .

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  12. #12
    VIP Member Array Bud White's Avatar
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    heres the 1million $ question though why is 40 the worst for this ?

    I have my opinions and will share later have to leave soon

    theres more 9mm and 45 out there im sure than 40s all together but you dont hear about this usually in them just 40s

  13. #13
    VIP Member Array Redneck Repairs's Avatar
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    Bud so far .40 is the " winner " of that lottery due to it being a high pressure straight walled round that has been out there in numbers for years . The .357 may or not catch up since it is bottleneck and that helps reduce feeding stresses . I have personaly had setback in .40 , 9mm, .45 , and .380 off the top of my head , of all thiese i would expect the .40 to " kaboom " first due to the normal chamber pressure it operates under , especialy since there are no .40 sized frames , you take a 9mm engineered frame and mod it for the .40 for economic reasons , IMHO had the put the .40 into the .45 sized frames the rep for dramatic malfunctions would not be there . ( among other things you could slope the feed ramp to a less abrupt angle and have less impact on the nose of the bullet . ) For the space that most .40 cal handguns have tho they do ok if the shooter does his part and realises to swap out rounds .
    Make sure you get full value out of today , Do something worthwhile, because what you do today will cost you one day off the rest of your life .
    We only begin to understand folks after we stop and think .

    Criminals are looking for victims, not opponents.

  14. #14
    Member Array plblark's Avatar
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    this is troublesome with the 40 S&W because setback can really affect the pressure and the 40 is already close on the pressure curve from what I've read.
    For MN specific carry information and a great shooting community, check out forum.twincitiescarry.com

  15. #15
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    Jang,

    Thanks! I saw this in your link:

    "Sigarms Inc's personnel confirm that reloading the same round five or six times will cause the problems, noting that reloading the same round even once will void their warranty.

    Both manufacturers stress that the problem is not with the gun, but with chambering the same round repeatedly. The NJ Regional Operations Intelligence Center urges all law enforcement officers not to chamber the same round when loading their weapons."


    I have NEVER heard of a warranty being voided if you chamber a round more than once. I'm not saying it's not true, I'm just saying that in all the years I've been carrying and conversing with people that carry, I've never once heard this mentioned. Hmmm, maybe we should read our owners manual.

    I have, as I'm sure countless others have, reloaded the same defensive round many times. Until I noticed set back on my M&P, I have never seen set back in my defensive ammo.

    For those of us that must load and unload our guns on a daily basis, I have to sometimes more than once, we're gonna go broke buying SD ammo. For example, if I have to chamber a new round every day, in less than three weeks, I would have gone through an entire box (20 rounds) of SD ammo. Since I can't chamber a round twice, that means it will cost me about $22 ($15 per 20, 30 days per month) a month just to keep once chambered rounds in my gun.
    I'm too young to be this old!
    Getting old isn't good for you!

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