MP5 bolt gap and cycling / function performance
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Thread: MP5 bolt gap and cycling / function performance

  1. #1
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    Default MP5 bolt gap and cycling / function performance

    Looking for experience shared by other armourers on the relation between bolt gap and function

    From my understanding, the MP5 has a "sweet spot" for the bolt gap at 0.25mm.

    HK literature specified 0.25mm to 0.50mm as the range for the bolt gap.

    From personal experience; Failures to Cycle (FTC) occurs slightly higher at below 0.25mm and above 0.45mm.

    Below 0.25mm (from what I am told) causes more damage to the brass by higher charge and pressure between chamber fluting.

    Does anyone else have experience on this and can share any relation between bolt gap and Failures in function?

  2. #2
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    In a nutshell....tooooooo much gap is a disaster and in 9mm tooooooo little gap can still function but is not optimal......beyond that you are over thinking
    Heckler & Koch Shooting Team
    Heckler & Koch Certified Armorer

  3. #3
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    Cycling can be affected by the ejection lever and tolerances. I had a clone that was a jamomatic! I replaced the trigger group with a HK model and all issues were resolved. Runs flawlessly now!

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    Quote Originally Posted by Jdyer View Post
    Cycling can be affected by the ejection lever and tolerances. I had a clone that was a jamomatic! I replaced the trigger group with a HK model and all issues were resolved. Runs flawlessly now!
    Cool, glad you got it worked out

    Some background to explain the OP, basically I wanted to experiment with the relation of bolt gap to cycling issue alone so I loaded 9mms to charges that would barely cycle. THen went down one roller size to see if it would completely stop cycling.

    Results are inconclusive at this point (still more testing to do)

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