AR pistol buffer tube length

Discussion in 'Rifle Country' started by needmorecowbell, Feb 22, 2022.

  1. needmorecowbell

    needmorecowbell Member

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    E7F8EA7C-6083-4999-BA44-4F27D12AE1A4.jpeg Hi all. Need some help trying to solve a problem. I have a Freedom Ordnance FX9 PCC that came with a KAK blade and buffer tube. The tube has threads that are about 1 3/8 in length. I have since bought an SBA3 and SOB brace that came with an aftermarket tube and the threads are only about 1 inch in length. I’m told this is standard tube thread length and not the 1 3/8? Does anyone know if this is true? Possibly a standard tube won’t work on the FX9. Definitely the rear of the receiver from end to buffer pin is longer on FX9 than AR but everything I read on internet says it takes a standard tube. The tubes I have are too short on threads when add castle nut and retainer plate.
     
  2. sarduy

    sarduy Member

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    The length of the threads doesn’t matter much as long as they reach the buffer detent, however what you have is not milspec or commercial, it’s an adaptation tube for the KAK brace and the threads are longer because that tube and brace can be put on many other type of weapons.

    commercial threads are a bit longer than milspec but all work the same, the difference is in the tube size, commercial been a little larger.

    your SBA3 most likely came with the milspec buffer tube and it’s 100% good to go with that thread size.

    BFEE37F9-8E6A-41BE-AAA2-9C4B1AC11F0E.png

    upload_2022-2-22_15-52-35.jpeg
     
    Last edited: Feb 22, 2022
    entropy and BigBlue 94 like this.
  3. needmorecowbell

    needmorecowbell Member

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    That’s my issue they don’t. The distance from receiver end to detent is longer on the FX9. I think I just need to find an adjustable tube with longer threads. Sent a message to Freedom Ordnance as they now have a model that comes with SBA3 so gotta be something that works
     
  4. sarduy

    sarduy Member

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    Have you tried screwing the buffer tube into the lower? If so can you post pictures?
     
  5. needmorecowbell

    needmorecowbell Member

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    Update: it does fit on my FX9 but not by much. My struggles were because by time it’s over buffer detent the retainer is almost tight to receiver making it impossible for a novice like me to keep the pin spring in. I was saved though by the internet as saw how you can tap the pin spring hole with a 4-40 tap and put a set screw in to keep spring in place so easy to thread tube with retainer. Did that today and problem solved
     
    BigBlue 94 likes this.
  6. BigBlue 94

    BigBlue 94 Member

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    I use 6-32 instead of 4-40 because those are the set screws i have. I usually cut the spring flush with the receiver because the set screw compresses it farther than spec. It can cause the pin to become very tight.
     
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